diff options
Diffstat (limited to 'contrib/pg_stat_statements/pg_stat_statements.c')
| -rw-r--r-- | contrib/pg_stat_statements/pg_stat_statements.c | 3447 |
1 files changed, 3447 insertions, 0 deletions
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c new file mode 100644 index 0000000..14cad19 --- /dev/null +++ b/contrib/pg_stat_statements/pg_stat_statements.c @@ -0,0 +1,3447 @@ +/*------------------------------------------------------------------------- + * + * pg_stat_statements.c + * Track statement planning and execution times as well as resource + * usage across a whole database cluster. + * + * Execution costs are totaled for each distinct source query, and kept in + * a shared hashtable. (We track only as many distinct queries as will fit + * in the designated amount of shared memory.) + * + * As of Postgres 9.2, this module normalizes query entries. Normalization + * is a process whereby similar queries, typically differing only in their + * constants (though the exact rules are somewhat more subtle than that) are + * recognized as equivalent, and are tracked as a single entry. This is + * particularly useful for non-prepared queries. + * + * Normalization is implemented by fingerprinting queries, selectively + * serializing those fields of each query tree's nodes that are judged to be + * essential to the query. This is referred to as a query jumble. This is + * distinct from a regular serialization in that various extraneous + * information is ignored as irrelevant or not essential to the query, such + * as the collations of Vars and, most notably, the values of constants. + * + * This jumble is acquired at the end of parse analysis of each query, and + * a 64-bit hash of it is stored into the query's Query.queryId field. + * The server then copies this value around, making it available in plan + * tree(s) generated from the query. The executor can then use this value + * to blame query costs on the proper queryId. + * + * To facilitate presenting entries to users, we create "representative" query + * strings in which constants are replaced with parameter symbols ($n), to + * make it clearer what a normalized entry can represent. To save on shared + * memory, and to avoid having to truncate oversized query strings, we store + * these strings in a temporary external query-texts file. Offsets into this + * file are kept in shared memory. + * + * Note about locking issues: to create or delete an entry in the shared + * hashtable, one must hold pgss->lock exclusively. Modifying any field + * in an entry except the counters requires the same. To look up an entry, + * one must hold the lock shared. To read or update the counters within + * an entry, one must hold the lock shared or exclusive (so the entry doesn't + * disappear!) and also take the entry's mutex spinlock. + * The shared state variable pgss->extent (the next free spot in the external + * query-text file) should be accessed only while holding either the + * pgss->mutex spinlock, or exclusive lock on pgss->lock. We use the mutex to + * allow reserving file space while holding only shared lock on pgss->lock. + * Rewriting the entire external query-text file, eg for garbage collection, + * requires holding pgss->lock exclusively; this allows individual entries + * in the file to be read or written while holding only shared lock. + * + * + * Copyright (c) 2008-2020, PostgreSQL Global Development Group + * + * IDENTIFICATION + * contrib/pg_stat_statements/pg_stat_statements.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include <math.h> +#include <sys/stat.h> +#include <unistd.h> + +#include "catalog/pg_authid.h" +#include "common/hashfn.h" +#include "executor/instrument.h" +#include "funcapi.h" +#include "mb/pg_wchar.h" +#include "miscadmin.h" +#include "optimizer/planner.h" +#include "parser/analyze.h" +#include "parser/parsetree.h" +#include "parser/scanner.h" +#include "parser/scansup.h" +#include "pgstat.h" +#include "storage/fd.h" +#include "storage/ipc.h" +#include "storage/spin.h" +#include "tcop/utility.h" +#include "utils/acl.h" +#include "utils/builtins.h" +#include "utils/memutils.h" + +PG_MODULE_MAGIC; + +/* Location of permanent stats file (valid when database is shut down) */ +#define PGSS_DUMP_FILE PGSTAT_STAT_PERMANENT_DIRECTORY "/pg_stat_statements.stat" + +/* + * Location of external query text file. We don't keep it in the core + * system's stats_temp_directory. The core system can safely use that GUC + * setting, because the statistics collector temp file paths are set only once + * as part of changing the GUC, but pg_stat_statements has no way of avoiding + * race conditions. Besides, we only expect modest, infrequent I/O for query + * strings, so placing the file on a faster filesystem is not compelling. + */ +#define PGSS_TEXT_FILE PG_STAT_TMP_DIR "/pgss_query_texts.stat" + +/* Magic number identifying the stats file format */ +static const uint32 PGSS_FILE_HEADER = 0x20171004; + +/* PostgreSQL major version number, changes in which invalidate all entries */ +static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100; + +/* XXX: Should USAGE_EXEC reflect execution time and/or buffer usage? */ +#define USAGE_EXEC(duration) (1.0) +#define USAGE_INIT (1.0) /* including initial planning */ +#define ASSUMED_MEDIAN_INIT (10.0) /* initial assumed median usage */ +#define ASSUMED_LENGTH_INIT 1024 /* initial assumed mean query length */ +#define USAGE_DECREASE_FACTOR (0.99) /* decreased every entry_dealloc */ +#define STICKY_DECREASE_FACTOR (0.50) /* factor for sticky entries */ +#define USAGE_DEALLOC_PERCENT 5 /* free this % of entries at once */ +#define IS_STICKY(c) ((c.calls[PGSS_PLAN] + c.calls[PGSS_EXEC]) == 0) + +#define JUMBLE_SIZE 1024 /* query serialization buffer size */ + +/* + * Extension version number, for supporting older extension versions' objects + */ +typedef enum pgssVersion +{ + PGSS_V1_0 = 0, + PGSS_V1_1, + PGSS_V1_2, + PGSS_V1_3, + PGSS_V1_8 +} pgssVersion; + +typedef enum pgssStoreKind +{ + PGSS_INVALID = -1, + + /* + * PGSS_PLAN and PGSS_EXEC must be respectively 0 and 1 as they're used to + * reference the underlying values in the arrays in the Counters struct, + * and this order is required in pg_stat_statements_internal(). + */ + PGSS_PLAN = 0, + PGSS_EXEC, + + PGSS_NUMKIND /* Must be last value of this enum */ +} pgssStoreKind; + +/* + * Hashtable key that defines the identity of a hashtable entry. We separate + * queries by user and by database even if they are otherwise identical. + * + * Right now, this structure contains no padding. If you add any, make sure + * to teach pgss_store() to zero the padding bytes. Otherwise, things will + * break, because pgss_hash is created using HASH_BLOBS, and thus tag_hash + * is used to hash this. + */ +typedef struct pgssHashKey +{ + Oid userid; /* user OID */ + Oid dbid; /* database OID */ + uint64 queryid; /* query identifier */ +} pgssHashKey; + +/* + * The actual stats counters kept within pgssEntry. + */ +typedef struct Counters +{ + int64 calls[PGSS_NUMKIND]; /* # of times planned/executed */ + double total_time[PGSS_NUMKIND]; /* total planning/execution time, + * in msec */ + double min_time[PGSS_NUMKIND]; /* minimum planning/execution time in + * msec */ + double max_time[PGSS_NUMKIND]; /* maximum planning/execution time in + * msec */ + double mean_time[PGSS_NUMKIND]; /* mean planning/execution time in + * msec */ + double sum_var_time[PGSS_NUMKIND]; /* sum of variances in + * planning/execution time in msec */ + int64 rows; /* total # of retrieved or affected rows */ + int64 shared_blks_hit; /* # of shared buffer hits */ + int64 shared_blks_read; /* # of shared disk blocks read */ + int64 shared_blks_dirtied; /* # of shared disk blocks dirtied */ + int64 shared_blks_written; /* # of shared disk blocks written */ + int64 local_blks_hit; /* # of local buffer hits */ + int64 local_blks_read; /* # of local disk blocks read */ + int64 local_blks_dirtied; /* # of local disk blocks dirtied */ + int64 local_blks_written; /* # of local disk blocks written */ + int64 temp_blks_read; /* # of temp blocks read */ + int64 temp_blks_written; /* # of temp blocks written */ + double blk_read_time; /* time spent reading, in msec */ + double blk_write_time; /* time spent writing, in msec */ + double usage; /* usage factor */ + int64 wal_records; /* # of WAL records generated */ + int64 wal_fpi; /* # of WAL full page images generated */ + uint64 wal_bytes; /* total amount of WAL bytes generated */ +} Counters; + +/* + * Statistics per statement + * + * Note: in event of a failure in garbage collection of the query text file, + * we reset query_offset to zero and query_len to -1. This will be seen as + * an invalid state by qtext_fetch(). + */ +typedef struct pgssEntry +{ + pgssHashKey key; /* hash key of entry - MUST BE FIRST */ + Counters counters; /* the statistics for this query */ + Size query_offset; /* query text offset in external file */ + int query_len; /* # of valid bytes in query string, or -1 */ + int encoding; /* query text encoding */ + slock_t mutex; /* protects the counters only */ +} pgssEntry; + +/* + * Global shared state + */ +typedef struct pgssSharedState +{ + LWLock *lock; /* protects hashtable search/modification */ + double cur_median_usage; /* current median usage in hashtable */ + Size mean_query_len; /* current mean entry text length */ + slock_t mutex; /* protects following fields only: */ + Size extent; /* current extent of query file */ + int n_writers; /* number of active writers to query file */ + int gc_count; /* query file garbage collection cycle count */ +} pgssSharedState; + +/* + * Struct for tracking locations/lengths of constants during normalization + */ +typedef struct pgssLocationLen +{ + int location; /* start offset in query text */ + int length; /* length in bytes, or -1 to ignore */ +} pgssLocationLen; + +/* + * Working state for computing a query jumble and producing a normalized + * query string + */ +typedef struct pgssJumbleState +{ + /* Jumble of current query tree */ + unsigned char *jumble; + + /* Number of bytes used in jumble[] */ + Size jumble_len; + + /* Array of locations of constants that should be removed */ + pgssLocationLen *clocations; + + /* Allocated length of clocations array */ + int clocations_buf_size; + + /* Current number of valid entries in clocations array */ + int clocations_count; + + /* highest Param id we've seen, in order to start normalization correctly */ + int highest_extern_param_id; +} pgssJumbleState; + +/*---- Local variables ----*/ + +/* Current nesting depth of ExecutorRun+ProcessUtility calls */ +static int exec_nested_level = 0; + +/* Current nesting depth of planner calls */ +static int plan_nested_level = 0; + +/* Saved hook values in case of unload */ +static shmem_startup_hook_type prev_shmem_startup_hook = NULL; +static post_parse_analyze_hook_type prev_post_parse_analyze_hook = NULL; +static planner_hook_type prev_planner_hook = NULL; +static ExecutorStart_hook_type prev_ExecutorStart = NULL; +static ExecutorRun_hook_type prev_ExecutorRun = NULL; +static ExecutorFinish_hook_type prev_ExecutorFinish = NULL; +static ExecutorEnd_hook_type prev_ExecutorEnd = NULL; +static ProcessUtility_hook_type prev_ProcessUtility = NULL; + +/* Links to shared memory state */ +static pgssSharedState *pgss = NULL; +static HTAB *pgss_hash = NULL; + +/*---- GUC variables ----*/ + +typedef enum +{ + PGSS_TRACK_NONE, /* track no statements */ + PGSS_TRACK_TOP, /* only top level statements */ + PGSS_TRACK_ALL /* all statements, including nested ones */ +} PGSSTrackLevel; + +static const struct config_enum_entry track_options[] = +{ + {"none", PGSS_TRACK_NONE, false}, + {"top", PGSS_TRACK_TOP, false}, + {"all", PGSS_TRACK_ALL, false}, + {NULL, 0, false} +}; + +static int pgss_max; /* max # statements to track */ +static int pgss_track; /* tracking level */ +static bool pgss_track_utility; /* whether to track utility commands */ +static bool pgss_track_planning; /* whether to track planning duration */ +static bool pgss_save; /* whether to save stats across shutdown */ + + +#define pgss_enabled(level) \ + (pgss_track == PGSS_TRACK_ALL || \ + (pgss_track == PGSS_TRACK_TOP && (level) == 0)) + +#define record_gc_qtexts() \ + do { \ + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; \ + SpinLockAcquire(&s->mutex); \ + s->gc_count++; \ + SpinLockRelease(&s->mutex); \ + } while(0) + +/*---- Function declarations ----*/ + +void _PG_init(void); +void _PG_fini(void); + +PG_FUNCTION_INFO_V1(pg_stat_statements_reset); +PG_FUNCTION_INFO_V1(pg_stat_statements_reset_1_7); +PG_FUNCTION_INFO_V1(pg_stat_statements_1_2); +PG_FUNCTION_INFO_V1(pg_stat_statements_1_3); +PG_FUNCTION_INFO_V1(pg_stat_statements_1_8); +PG_FUNCTION_INFO_V1(pg_stat_statements); + +static void pgss_shmem_startup(void); +static void pgss_shmem_shutdown(int code, Datum arg); +static void pgss_post_parse_analyze(ParseState *pstate, Query *query); +static PlannedStmt *pgss_planner(Query *parse, + const char *query_string, + int cursorOptions, + ParamListInfo boundParams); +static void pgss_ExecutorStart(QueryDesc *queryDesc, int eflags); +static void pgss_ExecutorRun(QueryDesc *queryDesc, + ScanDirection direction, + uint64 count, bool execute_once); +static void pgss_ExecutorFinish(QueryDesc *queryDesc); +static void pgss_ExecutorEnd(QueryDesc *queryDesc); +static void pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString, + ProcessUtilityContext context, ParamListInfo params, + QueryEnvironment *queryEnv, + DestReceiver *dest, QueryCompletion *qc); +static uint64 pgss_hash_string(const char *str, int len); +static void pgss_store(const char *query, uint64 queryId, + int query_location, int query_len, + pgssStoreKind kind, + double total_time, uint64 rows, + const BufferUsage *bufusage, + const WalUsage *walusage, + pgssJumbleState *jstate); +static void pg_stat_statements_internal(FunctionCallInfo fcinfo, + pgssVersion api_version, + bool showtext); +static Size pgss_memsize(void); +static pgssEntry *entry_alloc(pgssHashKey *key, Size query_offset, int query_len, + int encoding, bool sticky); +static void entry_dealloc(void); +static bool qtext_store(const char *query, int query_len, + Size *query_offset, int *gc_count); +static char *qtext_load_file(Size *buffer_size); +static char *qtext_fetch(Size query_offset, int query_len, + char *buffer, Size buffer_size); +static bool need_gc_qtexts(void); +static void gc_qtexts(void); +static void entry_reset(Oid userid, Oid dbid, uint64 queryid); +static void AppendJumble(pgssJumbleState *jstate, + const unsigned char *item, Size size); +static void JumbleQuery(pgssJumbleState *jstate, Query *query); +static void JumbleRangeTable(pgssJumbleState *jstate, List *rtable); +static void JumbleRowMarks(pgssJumbleState *jstate, List *rowMarks); +static void JumbleExpr(pgssJumbleState *jstate, Node *node); +static void RecordConstLocation(pgssJumbleState *jstate, int location); +static char *generate_normalized_query(pgssJumbleState *jstate, const char *query, + int query_loc, int *query_len_p, int encoding); +static void fill_in_constant_lengths(pgssJumbleState *jstate, const char *query, + int query_loc); +static int comp_location(const void *a, const void *b); + + +/* + * Module load callback + */ +void +_PG_init(void) +{ + /* + * In order to create our shared memory area, we have to be loaded via + * shared_preload_libraries. If not, fall out without hooking into any of + * the main system. (We don't throw error here because it seems useful to + * allow the pg_stat_statements functions to be created even when the + * module isn't active. The functions must protect themselves against + * being called then, however.) + */ + if (!process_shared_preload_libraries_in_progress) + return; + + /* + * Define (or redefine) custom GUC variables. + */ + DefineCustomIntVariable("pg_stat_statements.max", + "Sets the maximum number of statements tracked by pg_stat_statements.", + NULL, + &pgss_max, + 5000, + 100, + INT_MAX, + PGC_POSTMASTER, + 0, + NULL, + NULL, + NULL); + + DefineCustomEnumVariable("pg_stat_statements.track", + "Selects which statements are tracked by pg_stat_statements.", + NULL, + &pgss_track, + PGSS_TRACK_TOP, + track_options, + PGC_SUSET, + 0, + NULL, + NULL, + NULL); + + DefineCustomBoolVariable("pg_stat_statements.track_utility", + "Selects whether utility commands are tracked by pg_stat_statements.", + NULL, + &pgss_track_utility, + true, + PGC_SUSET, + 0, + NULL, + NULL, + NULL); + + DefineCustomBoolVariable("pg_stat_statements.track_planning", + "Selects whether planning duration is tracked by pg_stat_statements.", + NULL, + &pgss_track_planning, + false, + PGC_SUSET, + 0, + NULL, + NULL, + NULL); + + DefineCustomBoolVariable("pg_stat_statements.save", + "Save pg_stat_statements statistics across server shutdowns.", + NULL, + &pgss_save, + true, + PGC_SIGHUP, + 0, + NULL, + NULL, + NULL); + + EmitWarningsOnPlaceholders("pg_stat_statements"); + + /* + * Request additional shared resources. (These are no-ops if we're not in + * the postmaster process.) We'll allocate or attach to the shared + * resources in pgss_shmem_startup(). + */ + RequestAddinShmemSpace(pgss_memsize()); + RequestNamedLWLockTranche("pg_stat_statements", 1); + + /* + * Install hooks. + */ + prev_shmem_startup_hook = shmem_startup_hook; + shmem_startup_hook = pgss_shmem_startup; + prev_post_parse_analyze_hook = post_parse_analyze_hook; + post_parse_analyze_hook = pgss_post_parse_analyze; + prev_planner_hook = planner_hook; + planner_hook = pgss_planner; + prev_ExecutorStart = ExecutorStart_hook; + ExecutorStart_hook = pgss_ExecutorStart; + prev_ExecutorRun = ExecutorRun_hook; + ExecutorRun_hook = pgss_ExecutorRun; + prev_ExecutorFinish = ExecutorFinish_hook; + ExecutorFinish_hook = pgss_ExecutorFinish; + prev_ExecutorEnd = ExecutorEnd_hook; + ExecutorEnd_hook = pgss_ExecutorEnd; + prev_ProcessUtility = ProcessUtility_hook; + ProcessUtility_hook = pgss_ProcessUtility; +} + +/* + * Module unload callback + */ +void +_PG_fini(void) +{ + /* Uninstall hooks. */ + shmem_startup_hook = prev_shmem_startup_hook; + post_parse_analyze_hook = prev_post_parse_analyze_hook; + planner_hook = prev_planner_hook; + ExecutorStart_hook = prev_ExecutorStart; + ExecutorRun_hook = prev_ExecutorRun; + ExecutorFinish_hook = prev_ExecutorFinish; + ExecutorEnd_hook = prev_ExecutorEnd; + ProcessUtility_hook = prev_ProcessUtility; +} + +/* + * shmem_startup hook: allocate or attach to shared memory, + * then load any pre-existing statistics from file. + * Also create and load the query-texts file, which is expected to exist + * (even if empty) while the module is enabled. + */ +static void +pgss_shmem_startup(void) +{ + bool found; + HASHCTL info; + FILE *file = NULL; + FILE *qfile = NULL; + uint32 header; + int32 num; + int32 pgver; + int32 i; + int buffer_size; + char *buffer = NULL; + + if (prev_shmem_startup_hook) + prev_shmem_startup_hook(); + + /* reset in case this is a restart within the postmaster */ + pgss = NULL; + pgss_hash = NULL; + + /* + * Create or attach to the shared memory state, including hash table + */ + LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE); + + pgss = ShmemInitStruct("pg_stat_statements", + sizeof(pgssSharedState), + &found); + + if (!found) + { + /* First time through ... */ + pgss->lock = &(GetNamedLWLockTranche("pg_stat_statements"))->lock; + pgss->cur_median_usage = ASSUMED_MEDIAN_INIT; + pgss->mean_query_len = ASSUMED_LENGTH_INIT; + SpinLockInit(&pgss->mutex); + pgss->extent = 0; + pgss->n_writers = 0; + pgss->gc_count = 0; + } + + memset(&info, 0, sizeof(info)); + info.keysize = sizeof(pgssHashKey); + info.entrysize = sizeof(pgssEntry); + pgss_hash = ShmemInitHash("pg_stat_statements hash", + pgss_max, pgss_max, + &info, + HASH_ELEM | HASH_BLOBS); + + LWLockRelease(AddinShmemInitLock); + + /* + * If we're in the postmaster (or a standalone backend...), set up a shmem + * exit hook to dump the statistics to disk. + */ + if (!IsUnderPostmaster) + on_shmem_exit(pgss_shmem_shutdown, (Datum) 0); + + /* + * Done if some other process already completed our initialization. + */ + if (found) + return; + + /* + * Note: we don't bother with locks here, because there should be no other + * processes running when this code is reached. + */ + + /* Unlink query text file possibly left over from crash */ + unlink(PGSS_TEXT_FILE); + + /* Allocate new query text temp file */ + qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W); + if (qfile == NULL) + goto write_error; + + /* + * If we were told not to load old statistics, we're done. (Note we do + * not try to unlink any old dump file in this case. This seems a bit + * questionable but it's the historical behavior.) + */ + if (!pgss_save) + { + FreeFile(qfile); + return; + } + + /* + * Attempt to load old statistics from the dump file. + */ + file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_R); + if (file == NULL) + { + if (errno != ENOENT) + goto read_error; + /* No existing persisted stats file, so we're done */ + FreeFile(qfile); + return; + } + + buffer_size = 2048; + buffer = (char *) palloc(buffer_size); + + if (fread(&header, sizeof(uint32), 1, file) != 1 || + fread(&pgver, sizeof(uint32), 1, file) != 1 || + fread(&num, sizeof(int32), 1, file) != 1) + goto read_error; + + if (header != PGSS_FILE_HEADER || + pgver != PGSS_PG_MAJOR_VERSION) + goto data_error; + + for (i = 0; i < num; i++) + { + pgssEntry temp; + pgssEntry *entry; + Size query_offset; + + if (fread(&temp, sizeof(pgssEntry), 1, file) != 1) + goto read_error; + + /* Encoding is the only field we can easily sanity-check */ + if (!PG_VALID_BE_ENCODING(temp.encoding)) + goto data_error; + + /* Resize buffer as needed */ + if (temp.query_len >= buffer_size) + { + buffer_size = Max(buffer_size * 2, temp.query_len + 1); + buffer = repalloc(buffer, buffer_size); + } + + if (fread(buffer, 1, temp.query_len + 1, file) != temp.query_len + 1) + goto read_error; + + /* Should have a trailing null, but let's make sure */ + buffer[temp.query_len] = '\0'; + + /* Skip loading "sticky" entries */ + if (IS_STICKY(temp.counters)) + continue; + + /* Store the query text */ + query_offset = pgss->extent; + if (fwrite(buffer, 1, temp.query_len + 1, qfile) != temp.query_len + 1) + goto write_error; + pgss->extent += temp.query_len + 1; + + /* make the hashtable entry (discards old entries if too many) */ + entry = entry_alloc(&temp.key, query_offset, temp.query_len, + temp.encoding, + false); + + /* copy in the actual stats */ + entry->counters = temp.counters; + } + + pfree(buffer); + FreeFile(file); + FreeFile(qfile); + + /* + * Remove the persisted stats file so it's not included in + * backups/replication standbys, etc. A new file will be written on next + * shutdown. + * + * Note: it's okay if the PGSS_TEXT_FILE is included in a basebackup, + * because we remove that file on startup; it acts inversely to + * PGSS_DUMP_FILE, in that it is only supposed to be around when the + * server is running, whereas PGSS_DUMP_FILE is only supposed to be around + * when the server is not running. Leaving the file creates no danger of + * a newly restored database having a spurious record of execution costs, + * which is what we're really concerned about here. + */ + unlink(PGSS_DUMP_FILE); + + return; + +read_error: + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not read file \"%s\": %m", + PGSS_DUMP_FILE))); + goto fail; +data_error: + ereport(LOG, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("ignoring invalid data in file \"%s\"", + PGSS_DUMP_FILE))); + goto fail; +write_error: + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_TEXT_FILE))); +fail: + if (buffer) + pfree(buffer); + if (file) + FreeFile(file); + if (qfile) + FreeFile(qfile); + /* If possible, throw away the bogus file; ignore any error */ + unlink(PGSS_DUMP_FILE); + + /* + * Don't unlink PGSS_TEXT_FILE here; it should always be around while the + * server is running with pg_stat_statements enabled + */ +} + +/* + * shmem_shutdown hook: Dump statistics into file. + * + * Note: we don't bother with acquiring lock, because there should be no + * other processes running when this is called. + */ +static void +pgss_shmem_shutdown(int code, Datum arg) +{ + FILE *file; + char *qbuffer = NULL; + Size qbuffer_size = 0; + HASH_SEQ_STATUS hash_seq; + int32 num_entries; + pgssEntry *entry; + + /* Don't try to dump during a crash. */ + if (code) + return; + + /* Safety check ... shouldn't get here unless shmem is set up. */ + if (!pgss || !pgss_hash) + return; + + /* Don't dump if told not to. */ + if (!pgss_save) + return; + + file = AllocateFile(PGSS_DUMP_FILE ".tmp", PG_BINARY_W); + if (file == NULL) + goto error; + + if (fwrite(&PGSS_FILE_HEADER, sizeof(uint32), 1, file) != 1) + goto error; + if (fwrite(&PGSS_PG_MAJOR_VERSION, sizeof(uint32), 1, file) != 1) + goto error; + num_entries = hash_get_num_entries(pgss_hash); + if (fwrite(&num_entries, sizeof(int32), 1, file) != 1) + goto error; + + qbuffer = qtext_load_file(&qbuffer_size); + if (qbuffer == NULL) + goto error; + + /* + * When serializing to disk, we store query texts immediately after their + * entry data. Any orphaned query texts are thereby excluded. + */ + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + int len = entry->query_len; + char *qstr = qtext_fetch(entry->query_offset, len, + qbuffer, qbuffer_size); + + if (qstr == NULL) + continue; /* Ignore any entries with bogus texts */ + + if (fwrite(entry, sizeof(pgssEntry), 1, file) != 1 || + fwrite(qstr, 1, len + 1, file) != len + 1) + { + /* note: we assume hash_seq_term won't change errno */ + hash_seq_term(&hash_seq); + goto error; + } + } + + free(qbuffer); + qbuffer = NULL; + + if (FreeFile(file)) + { + file = NULL; + goto error; + } + + /* + * Rename file into place, so we atomically replace any old one. + */ + (void) durable_rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE, LOG); + + /* Unlink query-texts file; it's not needed while shutdown */ + unlink(PGSS_TEXT_FILE); + + return; + +error: + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_DUMP_FILE ".tmp"))); + if (qbuffer) + free(qbuffer); + if (file) + FreeFile(file); + unlink(PGSS_DUMP_FILE ".tmp"); + unlink(PGSS_TEXT_FILE); +} + +/* + * Post-parse-analysis hook: mark query with a queryId + */ +static void +pgss_post_parse_analyze(ParseState *pstate, Query *query) +{ + pgssJumbleState jstate; + + if (prev_post_parse_analyze_hook) + prev_post_parse_analyze_hook(pstate, query); + + /* Assert we didn't do this already */ + Assert(query->queryId == UINT64CONST(0)); + + /* Safety check... */ + if (!pgss || !pgss_hash || !pgss_enabled(exec_nested_level)) + return; + + /* + * Utility statements get queryId zero. We do this even in cases where + * the statement contains an optimizable statement for which a queryId + * could be derived (such as EXPLAIN or DECLARE CURSOR). For such cases, + * runtime control will first go through ProcessUtility and then the + * executor, and we don't want the executor hooks to do anything, since we + * are already measuring the statement's costs at the utility level. + */ + if (query->utilityStmt) + { + query->queryId = UINT64CONST(0); + return; + } + + /* Set up workspace for query jumbling */ + jstate.jumble = (unsigned char *) palloc(JUMBLE_SIZE); + jstate.jumble_len = 0; + jstate.clocations_buf_size = 32; + jstate.clocations = (pgssLocationLen *) + palloc(jstate.clocations_buf_size * sizeof(pgssLocationLen)); + jstate.clocations_count = 0; + jstate.highest_extern_param_id = 0; + + /* Compute query ID and mark the Query node with it */ + JumbleQuery(&jstate, query); + query->queryId = + DatumGetUInt64(hash_any_extended(jstate.jumble, jstate.jumble_len, 0)); + + /* + * If we are unlucky enough to get a hash of zero, use 1 instead, to + * prevent confusion with the utility-statement case. + */ + if (query->queryId == UINT64CONST(0)) + query->queryId = UINT64CONST(1); + + /* + * If we were able to identify any ignorable constants, we immediately + * create a hash table entry for the query, so that we can record the + * normalized form of the query string. If there were no such constants, + * the normalized string would be the same as the query text anyway, so + * there's no need for an early entry. + */ + if (jstate.clocations_count > 0) + pgss_store(pstate->p_sourcetext, + query->queryId, + query->stmt_location, + query->stmt_len, + PGSS_INVALID, + 0, + 0, + NULL, + NULL, + &jstate); +} + +/* + * Planner hook: forward to regular planner, but measure planning time + * if needed. + */ +static PlannedStmt * +pgss_planner(Query *parse, + const char *query_string, + int cursorOptions, + ParamListInfo boundParams) +{ + PlannedStmt *result; + + /* + * We can't process the query if no query_string is provided, as + * pgss_store needs it. We also ignore query without queryid, as it would + * be treated as a utility statement, which may not be the case. + * + * Note that planner_hook can be called from the planner itself, so we + * have a specific nesting level for the planner. However, utility + * commands containing optimizable statements can also call the planner, + * same for regular DML (for instance for underlying foreign key queries). + * So testing the planner nesting level only is not enough to detect real + * top level planner call. + */ + if (pgss_enabled(plan_nested_level + exec_nested_level) + && pgss_track_planning && query_string + && parse->queryId != UINT64CONST(0)) + { + instr_time start; + instr_time duration; + BufferUsage bufusage_start, + bufusage; + WalUsage walusage_start, + walusage; + + /* We need to track buffer usage as the planner can access them. */ + bufusage_start = pgBufferUsage; + + /* + * Similarly the planner could write some WAL records in some cases + * (e.g. setting a hint bit with those being WAL-logged) + */ + walusage_start = pgWalUsage; + INSTR_TIME_SET_CURRENT(start); + + plan_nested_level++; + PG_TRY(); + { + if (prev_planner_hook) + result = prev_planner_hook(parse, query_string, cursorOptions, + boundParams); + else + result = standard_planner(parse, query_string, cursorOptions, + boundParams); + } + PG_FINALLY(); + { + plan_nested_level--; + } + PG_END_TRY(); + + INSTR_TIME_SET_CURRENT(duration); + INSTR_TIME_SUBTRACT(duration, start); + + /* calc differences of buffer counters. */ + memset(&bufusage, 0, sizeof(BufferUsage)); + BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start); + + /* calc differences of WAL counters. */ + memset(&walusage, 0, sizeof(WalUsage)); + WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start); + + pgss_store(query_string, + parse->queryId, + parse->stmt_location, + parse->stmt_len, + PGSS_PLAN, + INSTR_TIME_GET_MILLISEC(duration), + 0, + &bufusage, + &walusage, + NULL); + } + else + { + if (prev_planner_hook) + result = prev_planner_hook(parse, query_string, cursorOptions, + boundParams); + else + result = standard_planner(parse, query_string, cursorOptions, + boundParams); + } + + return result; +} + +/* + * ExecutorStart hook: start up tracking if needed + */ +static void +pgss_ExecutorStart(QueryDesc *queryDesc, int eflags) +{ + if (prev_ExecutorStart) + prev_ExecutorStart(queryDesc, eflags); + else + standard_ExecutorStart(queryDesc, eflags); + + /* + * If query has queryId zero, don't track it. This prevents double + * counting of optimizable statements that are directly contained in + * utility statements. + */ + if (pgss_enabled(exec_nested_level) && queryDesc->plannedstmt->queryId != UINT64CONST(0)) + { + /* + * Set up to track total elapsed time in ExecutorRun. Make sure the + * space is allocated in the per-query context so it will go away at + * ExecutorEnd. + */ + if (queryDesc->totaltime == NULL) + { + MemoryContext oldcxt; + + oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt); + queryDesc->totaltime = InstrAlloc(1, INSTRUMENT_ALL); + MemoryContextSwitchTo(oldcxt); + } + } +} + +/* + * ExecutorRun hook: all we need do is track nesting depth + */ +static void +pgss_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count, + bool execute_once) +{ + exec_nested_level++; + PG_TRY(); + { + if (prev_ExecutorRun) + prev_ExecutorRun(queryDesc, direction, count, execute_once); + else + standard_ExecutorRun(queryDesc, direction, count, execute_once); + } + PG_FINALLY(); + { + exec_nested_level--; + } + PG_END_TRY(); +} + +/* + * ExecutorFinish hook: all we need do is track nesting depth + */ +static void +pgss_ExecutorFinish(QueryDesc *queryDesc) +{ + exec_nested_level++; + PG_TRY(); + { + if (prev_ExecutorFinish) + prev_ExecutorFinish(queryDesc); + else + standard_ExecutorFinish(queryDesc); + } + PG_FINALLY(); + { + exec_nested_level--; + } + PG_END_TRY(); +} + +/* + * ExecutorEnd hook: store results if needed + */ +static void +pgss_ExecutorEnd(QueryDesc *queryDesc) +{ + uint64 queryId = queryDesc->plannedstmt->queryId; + + if (queryId != UINT64CONST(0) && queryDesc->totaltime && + pgss_enabled(exec_nested_level)) + { + /* + * Make sure stats accumulation is done. (Note: it's okay if several + * levels of hook all do this.) + */ + InstrEndLoop(queryDesc->totaltime); + + pgss_store(queryDesc->sourceText, + queryId, + queryDesc->plannedstmt->stmt_location, + queryDesc->plannedstmt->stmt_len, + PGSS_EXEC, + queryDesc->totaltime->total * 1000.0, /* convert to msec */ + queryDesc->estate->es_processed, + &queryDesc->totaltime->bufusage, + &queryDesc->totaltime->walusage, + NULL); + } + + if (prev_ExecutorEnd) + prev_ExecutorEnd(queryDesc); + else + standard_ExecutorEnd(queryDesc); +} + +/* + * ProcessUtility hook + */ +static void +pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString, + ProcessUtilityContext context, + ParamListInfo params, QueryEnvironment *queryEnv, + DestReceiver *dest, QueryCompletion *qc) +{ + Node *parsetree = pstmt->utilityStmt; + + /* + * If it's an EXECUTE statement, we don't track it and don't increment the + * nesting level. This allows the cycles to be charged to the underlying + * PREPARE instead (by the Executor hooks), which is much more useful. + * + * We also don't track execution of PREPARE. If we did, we would get one + * hash table entry for the PREPARE (with hash calculated from the query + * string), and then a different one with the same query string (but hash + * calculated from the query tree) would be used to accumulate costs of + * ensuing EXECUTEs. This would be confusing, and inconsistent with other + * cases where planning time is not included at all. + * + * Likewise, we don't track execution of DEALLOCATE. + */ + if (pgss_track_utility && pgss_enabled(exec_nested_level) && + !IsA(parsetree, ExecuteStmt) && + !IsA(parsetree, PrepareStmt) && + !IsA(parsetree, DeallocateStmt)) + { + instr_time start; + instr_time duration; + uint64 rows; + BufferUsage bufusage_start, + bufusage; + WalUsage walusage_start, + walusage; + + bufusage_start = pgBufferUsage; + walusage_start = pgWalUsage; + INSTR_TIME_SET_CURRENT(start); + + exec_nested_level++; + PG_TRY(); + { + if (prev_ProcessUtility) + prev_ProcessUtility(pstmt, queryString, + context, params, queryEnv, + dest, qc); + else + standard_ProcessUtility(pstmt, queryString, + context, params, queryEnv, + dest, qc); + } + PG_FINALLY(); + { + exec_nested_level--; + } + PG_END_TRY(); + + INSTR_TIME_SET_CURRENT(duration); + INSTR_TIME_SUBTRACT(duration, start); + + rows = (qc && qc->commandTag == CMDTAG_COPY) ? qc->nprocessed : 0; + + /* calc differences of buffer counters. */ + memset(&bufusage, 0, sizeof(BufferUsage)); + BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start); + + /* calc differences of WAL counters. */ + memset(&walusage, 0, sizeof(WalUsage)); + WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start); + + pgss_store(queryString, + 0, /* signal that it's a utility stmt */ + pstmt->stmt_location, + pstmt->stmt_len, + PGSS_EXEC, + INSTR_TIME_GET_MILLISEC(duration), + rows, + &bufusage, + &walusage, + NULL); + } + else + { + if (prev_ProcessUtility) + prev_ProcessUtility(pstmt, queryString, + context, params, queryEnv, + dest, qc); + else + standard_ProcessUtility(pstmt, queryString, + context, params, queryEnv, + dest, qc); + } +} + +/* + * Given an arbitrarily long query string, produce a hash for the purposes of + * identifying the query, without normalizing constants. Used when hashing + * utility statements. + */ +static uint64 +pgss_hash_string(const char *str, int len) +{ + return DatumGetUInt64(hash_any_extended((const unsigned char *) str, + len, 0)); +} + +/* + * Store some statistics for a statement. + * + * If queryId is 0 then this is a utility statement and we should compute + * a suitable queryId internally. + * + * If jstate is not NULL then we're trying to create an entry for which + * we have no statistics as yet; we just want to record the normalized + * query string. total_time, rows, bufusage and walusage are ignored in this + * case. + * + * If kind is PGSS_PLAN or PGSS_EXEC, its value is used as the array position + * for the arrays in the Counters field. + */ +static void +pgss_store(const char *query, uint64 queryId, + int query_location, int query_len, + pgssStoreKind kind, + double total_time, uint64 rows, + const BufferUsage *bufusage, + const WalUsage *walusage, + pgssJumbleState *jstate) +{ + pgssHashKey key; + pgssEntry *entry; + char *norm_query = NULL; + int encoding = GetDatabaseEncoding(); + + Assert(query != NULL); + + /* Safety check... */ + if (!pgss || !pgss_hash) + return; + + /* + * Confine our attention to the relevant part of the string, if the query + * is a portion of a multi-statement source string. + * + * First apply starting offset, unless it's -1 (unknown). + */ + if (query_location >= 0) + { + Assert(query_location <= strlen(query)); + query += query_location; + /* Length of 0 (or -1) means "rest of string" */ + if (query_len <= 0) + query_len = strlen(query); + else + Assert(query_len <= strlen(query)); + } + else + { + /* If query location is unknown, distrust query_len as well */ + query_location = 0; + query_len = strlen(query); + } + + /* + * Discard leading and trailing whitespace, too. Use scanner_isspace() + * not libc's isspace(), because we want to match the lexer's behavior. + */ + while (query_len > 0 && scanner_isspace(query[0])) + query++, query_location++, query_len--; + while (query_len > 0 && scanner_isspace(query[query_len - 1])) + query_len--; + + /* + * For utility statements, we just hash the query string to get an ID. + */ + if (queryId == UINT64CONST(0)) + { + queryId = pgss_hash_string(query, query_len); + + /* + * If we are unlucky enough to get a hash of zero(invalid), use + * queryID as 2 instead, queryID 1 is already in use for normal + * statements. + */ + if (queryId == UINT64CONST(0)) + queryId = UINT64CONST(2); + } + + /* Set up key for hashtable search */ + key.userid = GetUserId(); + key.dbid = MyDatabaseId; + key.queryid = queryId; + + /* Lookup the hash table entry with shared lock. */ + LWLockAcquire(pgss->lock, LW_SHARED); + + entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_FIND, NULL); + + /* Create new entry, if not present */ + if (!entry) + { + Size query_offset; + int gc_count; + bool stored; + bool do_gc; + + /* + * Create a new, normalized query string if caller asked. We don't + * need to hold the lock while doing this work. (Note: in any case, + * it's possible that someone else creates a duplicate hashtable entry + * in the interval where we don't hold the lock below. That case is + * handled by entry_alloc.) + */ + if (jstate) + { + LWLockRelease(pgss->lock); + norm_query = generate_normalized_query(jstate, query, + query_location, + &query_len, + encoding); + LWLockAcquire(pgss->lock, LW_SHARED); + } + + /* Append new query text to file with only shared lock held */ + stored = qtext_store(norm_query ? norm_query : query, query_len, + &query_offset, &gc_count); + + /* + * Determine whether we need to garbage collect external query texts + * while the shared lock is still held. This micro-optimization + * avoids taking the time to decide this while holding exclusive lock. + */ + do_gc = need_gc_qtexts(); + + /* Need exclusive lock to make a new hashtable entry - promote */ + LWLockRelease(pgss->lock); + LWLockAcquire(pgss->lock, LW_EXCLUSIVE); + + /* + * A garbage collection may have occurred while we weren't holding the + * lock. In the unlikely event that this happens, the query text we + * stored above will have been garbage collected, so write it again. + * This should be infrequent enough that doing it while holding + * exclusive lock isn't a performance problem. + */ + if (!stored || pgss->gc_count != gc_count) + stored = qtext_store(norm_query ? norm_query : query, query_len, + &query_offset, NULL); + + /* If we failed to write to the text file, give up */ + if (!stored) + goto done; + + /* OK to create a new hashtable entry */ + entry = entry_alloc(&key, query_offset, query_len, encoding, + jstate != NULL); + + /* If needed, perform garbage collection while exclusive lock held */ + if (do_gc) + gc_qtexts(); + } + + /* Increment the counts, except when jstate is not NULL */ + if (!jstate) + { + /* + * Grab the spinlock while updating the counters (see comment about + * locking rules at the head of the file) + */ + volatile pgssEntry *e = (volatile pgssEntry *) entry; + + Assert(kind == PGSS_PLAN || kind == PGSS_EXEC); + + SpinLockAcquire(&e->mutex); + + /* "Unstick" entry if it was previously sticky */ + if (IS_STICKY(e->counters)) + e->counters.usage = USAGE_INIT; + + e->counters.calls[kind] += 1; + e->counters.total_time[kind] += total_time; + + if (e->counters.calls[kind] == 1) + { + e->counters.min_time[kind] = total_time; + e->counters.max_time[kind] = total_time; + e->counters.mean_time[kind] = total_time; + } + else + { + /* + * Welford's method for accurately computing variance. See + * <http://www.johndcook.com/blog/standard_deviation/> + */ + double old_mean = e->counters.mean_time[kind]; + + e->counters.mean_time[kind] += + (total_time - old_mean) / e->counters.calls[kind]; + e->counters.sum_var_time[kind] += + (total_time - old_mean) * (total_time - e->counters.mean_time[kind]); + + /* calculate min and max time */ + if (e->counters.min_time[kind] > total_time) + e->counters.min_time[kind] = total_time; + if (e->counters.max_time[kind] < total_time) + e->counters.max_time[kind] = total_time; + } + e->counters.rows += rows; + e->counters.shared_blks_hit += bufusage->shared_blks_hit; + e->counters.shared_blks_read += bufusage->shared_blks_read; + e->counters.shared_blks_dirtied += bufusage->shared_blks_dirtied; + e->counters.shared_blks_written += bufusage->shared_blks_written; + e->counters.local_blks_hit += bufusage->local_blks_hit; + e->counters.local_blks_read += bufusage->local_blks_read; + e->counters.local_blks_dirtied += bufusage->local_blks_dirtied; + e->counters.local_blks_written += bufusage->local_blks_written; + e->counters.temp_blks_read += bufusage->temp_blks_read; + e->counters.temp_blks_written += bufusage->temp_blks_written; + e->counters.blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_read_time); + e->counters.blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_write_time); + e->counters.usage += USAGE_EXEC(total_time); + e->counters.wal_records += walusage->wal_records; + e->counters.wal_fpi += walusage->wal_fpi; + e->counters.wal_bytes += walusage->wal_bytes; + + SpinLockRelease(&e->mutex); + } + +done: + LWLockRelease(pgss->lock); + + /* We postpone this clean-up until we're out of the lock */ + if (norm_query) + pfree(norm_query); +} + +/* + * Reset statement statistics corresponding to userid, dbid, and queryid. + */ +Datum +pg_stat_statements_reset_1_7(PG_FUNCTION_ARGS) +{ + Oid userid; + Oid dbid; + uint64 queryid; + + userid = PG_GETARG_OID(0); + dbid = PG_GETARG_OID(1); + queryid = (uint64) PG_GETARG_INT64(2); + + entry_reset(userid, dbid, queryid); + + PG_RETURN_VOID(); +} + +/* + * Reset statement statistics. + */ +Datum +pg_stat_statements_reset(PG_FUNCTION_ARGS) +{ + entry_reset(0, 0, 0); + + PG_RETURN_VOID(); +} + +/* Number of output arguments (columns) for various API versions */ +#define PG_STAT_STATEMENTS_COLS_V1_0 14 +#define PG_STAT_STATEMENTS_COLS_V1_1 18 +#define PG_STAT_STATEMENTS_COLS_V1_2 19 +#define PG_STAT_STATEMENTS_COLS_V1_3 23 +#define PG_STAT_STATEMENTS_COLS_V1_8 32 +#define PG_STAT_STATEMENTS_COLS 32 /* maximum of above */ + +/* + * Retrieve statement statistics. + * + * The SQL API of this function has changed multiple times, and will likely + * do so again in future. To support the case where a newer version of this + * loadable module is being used with an old SQL declaration of the function, + * we continue to support the older API versions. For 1.2 and later, the + * expected API version is identified by embedding it in the C name of the + * function. Unfortunately we weren't bright enough to do that for 1.1. + */ +Datum +pg_stat_statements_1_8(PG_FUNCTION_ARGS) +{ + bool showtext = PG_GETARG_BOOL(0); + + pg_stat_statements_internal(fcinfo, PGSS_V1_8, showtext); + + return (Datum) 0; +} + +Datum +pg_stat_statements_1_3(PG_FUNCTION_ARGS) +{ + bool showtext = PG_GETARG_BOOL(0); + + pg_stat_statements_internal(fcinfo, PGSS_V1_3, showtext); + + return (Datum) 0; +} + +Datum +pg_stat_statements_1_2(PG_FUNCTION_ARGS) +{ + bool showtext = PG_GETARG_BOOL(0); + + pg_stat_statements_internal(fcinfo, PGSS_V1_2, showtext); + + return (Datum) 0; +} + +/* + * Legacy entry point for pg_stat_statements() API versions 1.0 and 1.1. + * This can be removed someday, perhaps. + */ +Datum +pg_stat_statements(PG_FUNCTION_ARGS) +{ + /* If it's really API 1.1, we'll figure that out below */ + pg_stat_statements_internal(fcinfo, PGSS_V1_0, true); + + return (Datum) 0; +} + +/* Common code for all versions of pg_stat_statements() */ +static void +pg_stat_statements_internal(FunctionCallInfo fcinfo, + pgssVersion api_version, + bool showtext) +{ + ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; + TupleDesc tupdesc; + Tuplestorestate *tupstore; + MemoryContext per_query_ctx; + MemoryContext oldcontext; + Oid userid = GetUserId(); + bool is_allowed_role = false; + char *qbuffer = NULL; + Size qbuffer_size = 0; + Size extent = 0; + int gc_count = 0; + HASH_SEQ_STATUS hash_seq; + pgssEntry *entry; + + /* Superusers or members of pg_read_all_stats members are allowed */ + is_allowed_role = is_member_of_role(GetUserId(), DEFAULT_ROLE_READ_ALL_STATS); + + /* hash table must exist already */ + if (!pgss || !pgss_hash) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("pg_stat_statements must be loaded via shared_preload_libraries"))); + + /* check to see if caller supports us returning a tuplestore */ + if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo)) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("set-valued function called in context that cannot accept a set"))); + if (!(rsinfo->allowedModes & SFRM_Materialize)) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("materialize mode required, but it is not allowed in this context"))); + + /* Switch into long-lived context to construct returned data structures */ + per_query_ctx = rsinfo->econtext->ecxt_per_query_memory; + oldcontext = MemoryContextSwitchTo(per_query_ctx); + + /* Build a tuple descriptor for our result type */ + if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + /* + * Check we have the expected number of output arguments. Aside from + * being a good safety check, we need a kluge here to detect API version + * 1.1, which was wedged into the code in an ill-considered way. + */ + switch (tupdesc->natts) + { + case PG_STAT_STATEMENTS_COLS_V1_0: + if (api_version != PGSS_V1_0) + elog(ERROR, "incorrect number of output arguments"); + break; + case PG_STAT_STATEMENTS_COLS_V1_1: + /* pg_stat_statements() should have told us 1.0 */ + if (api_version != PGSS_V1_0) + elog(ERROR, "incorrect number of output arguments"); + api_version = PGSS_V1_1; + break; + case PG_STAT_STATEMENTS_COLS_V1_2: + if (api_version != PGSS_V1_2) + elog(ERROR, "incorrect number of output arguments"); + break; + case PG_STAT_STATEMENTS_COLS_V1_3: + if (api_version != PGSS_V1_3) + elog(ERROR, "incorrect number of output arguments"); + break; + case PG_STAT_STATEMENTS_COLS_V1_8: + if (api_version != PGSS_V1_8) + elog(ERROR, "incorrect number of output arguments"); + break; + default: + elog(ERROR, "incorrect number of output arguments"); + } + + tupstore = tuplestore_begin_heap(true, false, work_mem); + rsinfo->returnMode = SFRM_Materialize; + rsinfo->setResult = tupstore; + rsinfo->setDesc = tupdesc; + + MemoryContextSwitchTo(oldcontext); + + /* + * We'd like to load the query text file (if needed) while not holding any + * lock on pgss->lock. In the worst case we'll have to do this again + * after we have the lock, but it's unlikely enough to make this a win + * despite occasional duplicated work. We need to reload if anybody + * writes to the file (either a retail qtext_store(), or a garbage + * collection) between this point and where we've gotten shared lock. If + * a qtext_store is actually in progress when we look, we might as well + * skip the speculative load entirely. + */ + if (showtext) + { + int n_writers; + + /* Take the mutex so we can examine variables */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + extent = s->extent; + n_writers = s->n_writers; + gc_count = s->gc_count; + SpinLockRelease(&s->mutex); + } + + /* No point in loading file now if there are active writers */ + if (n_writers == 0) + qbuffer = qtext_load_file(&qbuffer_size); + } + + /* + * Get shared lock, load or reload the query text file if we must, and + * iterate over the hashtable entries. + * + * With a large hash table, we might be holding the lock rather longer + * than one could wish. However, this only blocks creation of new hash + * table entries, and the larger the hash table the less likely that is to + * be needed. So we can hope this is okay. Perhaps someday we'll decide + * we need to partition the hash table to limit the time spent holding any + * one lock. + */ + LWLockAcquire(pgss->lock, LW_SHARED); + + if (showtext) + { + /* + * Here it is safe to examine extent and gc_count without taking the + * mutex. Note that although other processes might change + * pgss->extent just after we look at it, the strings they then write + * into the file cannot yet be referenced in the hashtable, so we + * don't care whether we see them or not. + * + * If qtext_load_file fails, we just press on; we'll return NULL for + * every query text. + */ + if (qbuffer == NULL || + pgss->extent != extent || + pgss->gc_count != gc_count) + { + if (qbuffer) + free(qbuffer); + qbuffer = qtext_load_file(&qbuffer_size); + } + } + + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + Datum values[PG_STAT_STATEMENTS_COLS]; + bool nulls[PG_STAT_STATEMENTS_COLS]; + int i = 0; + Counters tmp; + double stddev; + int64 queryid = entry->key.queryid; + + memset(values, 0, sizeof(values)); + memset(nulls, 0, sizeof(nulls)); + + values[i++] = ObjectIdGetDatum(entry->key.userid); + values[i++] = ObjectIdGetDatum(entry->key.dbid); + + if (is_allowed_role || entry->key.userid == userid) + { + if (api_version >= PGSS_V1_2) + values[i++] = Int64GetDatumFast(queryid); + + if (showtext) + { + char *qstr = qtext_fetch(entry->query_offset, + entry->query_len, + qbuffer, + qbuffer_size); + + if (qstr) + { + char *enc; + + enc = pg_any_to_server(qstr, + entry->query_len, + entry->encoding); + + values[i++] = CStringGetTextDatum(enc); + + if (enc != qstr) + pfree(enc); + } + else + { + /* Just return a null if we fail to find the text */ + nulls[i++] = true; + } + } + else + { + /* Query text not requested */ + nulls[i++] = true; + } + } + else + { + /* Don't show queryid */ + if (api_version >= PGSS_V1_2) + nulls[i++] = true; + + /* + * Don't show query text, but hint as to the reason for not doing + * so if it was requested + */ + if (showtext) + values[i++] = CStringGetTextDatum("<insufficient privilege>"); + else + nulls[i++] = true; + } + + /* copy counters to a local variable to keep locking time short */ + { + volatile pgssEntry *e = (volatile pgssEntry *) entry; + + SpinLockAcquire(&e->mutex); + tmp = e->counters; + SpinLockRelease(&e->mutex); + } + + /* Skip entry if unexecuted (ie, it's a pending "sticky" entry) */ + if (IS_STICKY(tmp)) + continue; + + /* Note that we rely on PGSS_PLAN being 0 and PGSS_EXEC being 1. */ + for (int kind = 0; kind < PGSS_NUMKIND; kind++) + { + if (kind == PGSS_EXEC || api_version >= PGSS_V1_8) + { + values[i++] = Int64GetDatumFast(tmp.calls[kind]); + values[i++] = Float8GetDatumFast(tmp.total_time[kind]); + } + + if ((kind == PGSS_EXEC && api_version >= PGSS_V1_3) || + api_version >= PGSS_V1_8) + { + values[i++] = Float8GetDatumFast(tmp.min_time[kind]); + values[i++] = Float8GetDatumFast(tmp.max_time[kind]); + values[i++] = Float8GetDatumFast(tmp.mean_time[kind]); + + /* + * Note we are calculating the population variance here, not + * the sample variance, as we have data for the whole + * population, so Bessel's correction is not used, and we + * don't divide by tmp.calls - 1. + */ + if (tmp.calls[kind] > 1) + stddev = sqrt(tmp.sum_var_time[kind] / tmp.calls[kind]); + else + stddev = 0.0; + values[i++] = Float8GetDatumFast(stddev); + } + } + values[i++] = Int64GetDatumFast(tmp.rows); + values[i++] = Int64GetDatumFast(tmp.shared_blks_hit); + values[i++] = Int64GetDatumFast(tmp.shared_blks_read); + if (api_version >= PGSS_V1_1) + values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied); + values[i++] = Int64GetDatumFast(tmp.shared_blks_written); + values[i++] = Int64GetDatumFast(tmp.local_blks_hit); + values[i++] = Int64GetDatumFast(tmp.local_blks_read); + if (api_version >= PGSS_V1_1) + values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied); + values[i++] = Int64GetDatumFast(tmp.local_blks_written); + values[i++] = Int64GetDatumFast(tmp.temp_blks_read); + values[i++] = Int64GetDatumFast(tmp.temp_blks_written); + if (api_version >= PGSS_V1_1) + { + values[i++] = Float8GetDatumFast(tmp.blk_read_time); + values[i++] = Float8GetDatumFast(tmp.blk_write_time); + } + if (api_version >= PGSS_V1_8) + { + char buf[256]; + Datum wal_bytes; + + values[i++] = Int64GetDatumFast(tmp.wal_records); + values[i++] = Int64GetDatumFast(tmp.wal_fpi); + + snprintf(buf, sizeof buf, UINT64_FORMAT, tmp.wal_bytes); + + /* Convert to numeric. */ + wal_bytes = DirectFunctionCall3(numeric_in, + CStringGetDatum(buf), + ObjectIdGetDatum(0), + Int32GetDatum(-1)); + values[i++] = wal_bytes; + } + + Assert(i == (api_version == PGSS_V1_0 ? PG_STAT_STATEMENTS_COLS_V1_0 : + api_version == PGSS_V1_1 ? PG_STAT_STATEMENTS_COLS_V1_1 : + api_version == PGSS_V1_2 ? PG_STAT_STATEMENTS_COLS_V1_2 : + api_version == PGSS_V1_3 ? PG_STAT_STATEMENTS_COLS_V1_3 : + api_version == PGSS_V1_8 ? PG_STAT_STATEMENTS_COLS_V1_8 : + -1 /* fail if you forget to update this assert */ )); + + tuplestore_putvalues(tupstore, tupdesc, values, nulls); + } + + /* clean up and return the tuplestore */ + LWLockRelease(pgss->lock); + + if (qbuffer) + free(qbuffer); + + tuplestore_donestoring(tupstore); +} + +/* + * Estimate shared memory space needed. + */ +static Size +pgss_memsize(void) +{ + Size size; + + size = MAXALIGN(sizeof(pgssSharedState)); + size = add_size(size, hash_estimate_size(pgss_max, sizeof(pgssEntry))); + + return size; +} + +/* + * Allocate a new hashtable entry. + * caller must hold an exclusive lock on pgss->lock + * + * "query" need not be null-terminated; we rely on query_len instead + * + * If "sticky" is true, make the new entry artificially sticky so that it will + * probably still be there when the query finishes execution. We do this by + * giving it a median usage value rather than the normal value. (Strictly + * speaking, query strings are normalized on a best effort basis, though it + * would be difficult to demonstrate this even under artificial conditions.) + * + * Note: despite needing exclusive lock, it's not an error for the target + * entry to already exist. This is because pgss_store releases and + * reacquires lock after failing to find a match; so someone else could + * have made the entry while we waited to get exclusive lock. + */ +static pgssEntry * +entry_alloc(pgssHashKey *key, Size query_offset, int query_len, int encoding, + bool sticky) +{ + pgssEntry *entry; + bool found; + + /* Make space if needed */ + while (hash_get_num_entries(pgss_hash) >= pgss_max) + entry_dealloc(); + + /* Find or create an entry with desired hash code */ + entry = (pgssEntry *) hash_search(pgss_hash, key, HASH_ENTER, &found); + + if (!found) + { + /* New entry, initialize it */ + + /* reset the statistics */ + memset(&entry->counters, 0, sizeof(Counters)); + /* set the appropriate initial usage count */ + entry->counters.usage = sticky ? pgss->cur_median_usage : USAGE_INIT; + /* re-initialize the mutex each time ... we assume no one using it */ + SpinLockInit(&entry->mutex); + /* ... and don't forget the query text metadata */ + Assert(query_len >= 0); + entry->query_offset = query_offset; + entry->query_len = query_len; + entry->encoding = encoding; + } + + return entry; +} + +/* + * qsort comparator for sorting into increasing usage order + */ +static int +entry_cmp(const void *lhs, const void *rhs) +{ + double l_usage = (*(pgssEntry *const *) lhs)->counters.usage; + double r_usage = (*(pgssEntry *const *) rhs)->counters.usage; + + if (l_usage < r_usage) + return -1; + else if (l_usage > r_usage) + return +1; + else + return 0; +} + +/* + * Deallocate least-used entries. + * + * Caller must hold an exclusive lock on pgss->lock. + */ +static void +entry_dealloc(void) +{ + HASH_SEQ_STATUS hash_seq; + pgssEntry **entries; + pgssEntry *entry; + int nvictims; + int i; + Size tottextlen; + int nvalidtexts; + + /* + * Sort entries by usage and deallocate USAGE_DEALLOC_PERCENT of them. + * While we're scanning the table, apply the decay factor to the usage + * values, and update the mean query length. + * + * Note that the mean query length is almost immediately obsolete, since + * we compute it before not after discarding the least-used entries. + * Hopefully, that doesn't affect the mean too much; it doesn't seem worth + * making two passes to get a more current result. Likewise, the new + * cur_median_usage includes the entries we're about to zap. + */ + + entries = palloc(hash_get_num_entries(pgss_hash) * sizeof(pgssEntry *)); + + i = 0; + tottextlen = 0; + nvalidtexts = 0; + + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + entries[i++] = entry; + /* "Sticky" entries get a different usage decay rate. */ + if (IS_STICKY(entry->counters)) + entry->counters.usage *= STICKY_DECREASE_FACTOR; + else + entry->counters.usage *= USAGE_DECREASE_FACTOR; + /* In the mean length computation, ignore dropped texts. */ + if (entry->query_len >= 0) + { + tottextlen += entry->query_len + 1; + nvalidtexts++; + } + } + + /* Sort into increasing order by usage */ + qsort(entries, i, sizeof(pgssEntry *), entry_cmp); + + /* Record the (approximate) median usage */ + if (i > 0) + pgss->cur_median_usage = entries[i / 2]->counters.usage; + /* Record the mean query length */ + if (nvalidtexts > 0) + pgss->mean_query_len = tottextlen / nvalidtexts; + else + pgss->mean_query_len = ASSUMED_LENGTH_INIT; + + /* Now zap an appropriate fraction of lowest-usage entries */ + nvictims = Max(10, i * USAGE_DEALLOC_PERCENT / 100); + nvictims = Min(nvictims, i); + + for (i = 0; i < nvictims; i++) + { + hash_search(pgss_hash, &entries[i]->key, HASH_REMOVE, NULL); + } + + pfree(entries); +} + +/* + * Given a query string (not necessarily null-terminated), allocate a new + * entry in the external query text file and store the string there. + * + * If successful, returns true, and stores the new entry's offset in the file + * into *query_offset. Also, if gc_count isn't NULL, *gc_count is set to the + * number of garbage collections that have occurred so far. + * + * On failure, returns false. + * + * At least a shared lock on pgss->lock must be held by the caller, so as + * to prevent a concurrent garbage collection. Share-lock-holding callers + * should pass a gc_count pointer to obtain the number of garbage collections, + * so that they can recheck the count after obtaining exclusive lock to + * detect whether a garbage collection occurred (and removed this entry). + */ +static bool +qtext_store(const char *query, int query_len, + Size *query_offset, int *gc_count) +{ + Size off; + int fd; + + /* + * We use a spinlock to protect extent/n_writers/gc_count, so that + * multiple processes may execute this function concurrently. + */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + off = s->extent; + s->extent += query_len + 1; + s->n_writers++; + if (gc_count) + *gc_count = s->gc_count; + SpinLockRelease(&s->mutex); + } + + *query_offset = off; + + /* Now write the data into the successfully-reserved part of the file */ + fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDWR | O_CREAT | PG_BINARY); + if (fd < 0) + goto error; + + if (pg_pwrite(fd, query, query_len, off) != query_len) + goto error; + if (pg_pwrite(fd, "\0", 1, off + query_len) != 1) + goto error; + + CloseTransientFile(fd); + + /* Mark our write complete */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + s->n_writers--; + SpinLockRelease(&s->mutex); + } + + return true; + +error: + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_TEXT_FILE))); + + if (fd >= 0) + CloseTransientFile(fd); + + /* Mark our write complete */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + s->n_writers--; + SpinLockRelease(&s->mutex); + } + + return false; +} + +/* + * Read the external query text file into a malloc'd buffer. + * + * Returns NULL (without throwing an error) if unable to read, eg + * file not there or insufficient memory. + * + * On success, the buffer size is also returned into *buffer_size. + * + * This can be called without any lock on pgss->lock, but in that case + * the caller is responsible for verifying that the result is sane. + */ +static char * +qtext_load_file(Size *buffer_size) +{ + char *buf; + int fd; + struct stat stat; + + fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDONLY | PG_BINARY); + if (fd < 0) + { + if (errno != ENOENT) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not read file \"%s\": %m", + PGSS_TEXT_FILE))); + return NULL; + } + + /* Get file length */ + if (fstat(fd, &stat)) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not stat file \"%s\": %m", + PGSS_TEXT_FILE))); + CloseTransientFile(fd); + return NULL; + } + + /* Allocate buffer; beware that off_t might be wider than size_t */ + if (stat.st_size <= MaxAllocHugeSize) + buf = (char *) malloc(stat.st_size); + else + buf = NULL; + if (buf == NULL) + { + ereport(LOG, + (errcode(ERRCODE_OUT_OF_MEMORY), + errmsg("out of memory"), + errdetail("Could not allocate enough memory to read file \"%s\".", + PGSS_TEXT_FILE))); + CloseTransientFile(fd); + return NULL; + } + + /* + * OK, slurp in the file. If we get a short read and errno doesn't get + * set, the reason is probably that garbage collection truncated the file + * since we did the fstat(), so we don't log a complaint --- but we don't + * return the data, either, since it's most likely corrupt due to + * concurrent writes from garbage collection. + */ + errno = 0; + if (read(fd, buf, stat.st_size) != stat.st_size) + { + if (errno) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not read file \"%s\": %m", + PGSS_TEXT_FILE))); + free(buf); + CloseTransientFile(fd); + return NULL; + } + + if (CloseTransientFile(fd) != 0) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not close file \"%s\": %m", PGSS_TEXT_FILE))); + + *buffer_size = stat.st_size; + return buf; +} + +/* + * Locate a query text in the file image previously read by qtext_load_file(). + * + * We validate the given offset/length, and return NULL if bogus. Otherwise, + * the result points to a null-terminated string within the buffer. + */ +static char * +qtext_fetch(Size query_offset, int query_len, + char *buffer, Size buffer_size) +{ + /* File read failed? */ + if (buffer == NULL) + return NULL; + /* Bogus offset/length? */ + if (query_len < 0 || + query_offset + query_len >= buffer_size) + return NULL; + /* As a further sanity check, make sure there's a trailing null */ + if (buffer[query_offset + query_len] != '\0') + return NULL; + /* Looks OK */ + return buffer + query_offset; +} + +/* + * Do we need to garbage-collect the external query text file? + * + * Caller should hold at least a shared lock on pgss->lock. + */ +static bool +need_gc_qtexts(void) +{ + Size extent; + + /* Read shared extent pointer */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + extent = s->extent; + SpinLockRelease(&s->mutex); + } + + /* Don't proceed if file does not exceed 512 bytes per possible entry */ + if (extent < 512 * pgss_max) + return false; + + /* + * Don't proceed if file is less than about 50% bloat. Nothing can or + * should be done in the event of unusually large query texts accounting + * for file's large size. We go to the trouble of maintaining the mean + * query length in order to prevent garbage collection from thrashing + * uselessly. + */ + if (extent < pgss->mean_query_len * pgss_max * 2) + return false; + + return true; +} + +/* + * Garbage-collect orphaned query texts in external file. + * + * This won't be called often in the typical case, since it's likely that + * there won't be too much churn, and besides, a similar compaction process + * occurs when serializing to disk at shutdown or as part of resetting. + * Despite this, it seems prudent to plan for the edge case where the file + * becomes unreasonably large, with no other method of compaction likely to + * occur in the foreseeable future. + * + * The caller must hold an exclusive lock on pgss->lock. + * + * At the first sign of trouble we unlink the query text file to get a clean + * slate (although existing statistics are retained), rather than risk + * thrashing by allowing the same problem case to recur indefinitely. + */ +static void +gc_qtexts(void) +{ + char *qbuffer; + Size qbuffer_size; + FILE *qfile = NULL; + HASH_SEQ_STATUS hash_seq; + pgssEntry *entry; + Size extent; + int nentries; + + /* + * When called from pgss_store, some other session might have proceeded + * with garbage collection in the no-lock-held interim of lock strength + * escalation. Check once more that this is actually necessary. + */ + if (!need_gc_qtexts()) + return; + + /* + * Load the old texts file. If we fail (out of memory, for instance), + * invalidate query texts. Hopefully this is rare. It might seem better + * to leave things alone on an OOM failure, but the problem is that the + * file is only going to get bigger; hoping for a future non-OOM result is + * risky and can easily lead to complete denial of service. + */ + qbuffer = qtext_load_file(&qbuffer_size); + if (qbuffer == NULL) + goto gc_fail; + + /* + * We overwrite the query texts file in place, so as to reduce the risk of + * an out-of-disk-space failure. Since the file is guaranteed not to get + * larger, this should always work on traditional filesystems; though we + * could still lose on copy-on-write filesystems. + */ + qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W); + if (qfile == NULL) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_TEXT_FILE))); + goto gc_fail; + } + + extent = 0; + nentries = 0; + + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + int query_len = entry->query_len; + char *qry = qtext_fetch(entry->query_offset, + query_len, + qbuffer, + qbuffer_size); + + if (qry == NULL) + { + /* Trouble ... drop the text */ + entry->query_offset = 0; + entry->query_len = -1; + /* entry will not be counted in mean query length computation */ + continue; + } + + if (fwrite(qry, 1, query_len + 1, qfile) != query_len + 1) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_TEXT_FILE))); + hash_seq_term(&hash_seq); + goto gc_fail; + } + + entry->query_offset = extent; + extent += query_len + 1; + nentries++; + } + + /* + * Truncate away any now-unused space. If this fails for some odd reason, + * we log it, but there's no need to fail. + */ + if (ftruncate(fileno(qfile), extent) != 0) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not truncate file \"%s\": %m", + PGSS_TEXT_FILE))); + + if (FreeFile(qfile)) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write file \"%s\": %m", + PGSS_TEXT_FILE))); + qfile = NULL; + goto gc_fail; + } + + elog(DEBUG1, "pgss gc of queries file shrunk size from %zu to %zu", + pgss->extent, extent); + + /* Reset the shared extent pointer */ + pgss->extent = extent; + + /* + * Also update the mean query length, to be sure that need_gc_qtexts() + * won't still think we have a problem. + */ + if (nentries > 0) + pgss->mean_query_len = extent / nentries; + else + pgss->mean_query_len = ASSUMED_LENGTH_INIT; + + free(qbuffer); + + /* + * OK, count a garbage collection cycle. (Note: even though we have + * exclusive lock on pgss->lock, we must take pgss->mutex for this, since + * other processes may examine gc_count while holding only the mutex. + * Also, we have to advance the count *after* we've rewritten the file, + * else other processes might not realize they read a stale file.) + */ + record_gc_qtexts(); + + return; + +gc_fail: + /* clean up resources */ + if (qfile) + FreeFile(qfile); + if (qbuffer) + free(qbuffer); + + /* + * Since the contents of the external file are now uncertain, mark all + * hashtable entries as having invalid texts. + */ + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + entry->query_offset = 0; + entry->query_len = -1; + } + + /* + * Destroy the query text file and create a new, empty one + */ + (void) unlink(PGSS_TEXT_FILE); + qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W); + if (qfile == NULL) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not recreate file \"%s\": %m", + PGSS_TEXT_FILE))); + else + FreeFile(qfile); + + /* Reset the shared extent pointer */ + pgss->extent = 0; + + /* Reset mean_query_len to match the new state */ + pgss->mean_query_len = ASSUMED_LENGTH_INIT; + + /* + * Bump the GC count even though we failed. + * + * This is needed to make concurrent readers of file without any lock on + * pgss->lock notice existence of new version of file. Once readers + * subsequently observe a change in GC count with pgss->lock held, that + * forces a safe reopen of file. Writers also require that we bump here, + * of course. (As required by locking protocol, readers and writers don't + * trust earlier file contents until gc_count is found unchanged after + * pgss->lock acquired in shared or exclusive mode respectively.) + */ + record_gc_qtexts(); +} + +/* + * Release entries corresponding to parameters passed. + */ +static void +entry_reset(Oid userid, Oid dbid, uint64 queryid) +{ + HASH_SEQ_STATUS hash_seq; + pgssEntry *entry; + FILE *qfile; + long num_entries; + long num_remove = 0; + pgssHashKey key; + + if (!pgss || !pgss_hash) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("pg_stat_statements must be loaded via shared_preload_libraries"))); + + LWLockAcquire(pgss->lock, LW_EXCLUSIVE); + num_entries = hash_get_num_entries(pgss_hash); + + if (userid != 0 && dbid != 0 && queryid != UINT64CONST(0)) + { + /* If all the parameters are available, use the fast path. */ + key.userid = userid; + key.dbid = dbid; + key.queryid = queryid; + + /* Remove the key if exists */ + entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_REMOVE, NULL); + if (entry) /* found */ + num_remove++; + } + else if (userid != 0 || dbid != 0 || queryid != UINT64CONST(0)) + { + /* Remove entries corresponding to valid parameters. */ + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + if ((!userid || entry->key.userid == userid) && + (!dbid || entry->key.dbid == dbid) && + (!queryid || entry->key.queryid == queryid)) + { + hash_search(pgss_hash, &entry->key, HASH_REMOVE, NULL); + num_remove++; + } + } + } + else + { + /* Remove all entries. */ + hash_seq_init(&hash_seq, pgss_hash); + while ((entry = hash_seq_search(&hash_seq)) != NULL) + { + hash_search(pgss_hash, &entry->key, HASH_REMOVE, NULL); + num_remove++; + } + } + + /* All entries are removed? */ + if (num_entries != num_remove) + goto release_lock; + + /* + * Write new empty query file, perhaps even creating a new one to recover + * if the file was missing. + */ + qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W); + if (qfile == NULL) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not create file \"%s\": %m", + PGSS_TEXT_FILE))); + goto done; + } + + /* If ftruncate fails, log it, but it's not a fatal problem */ + if (ftruncate(fileno(qfile), 0) != 0) + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not truncate file \"%s\": %m", + PGSS_TEXT_FILE))); + + FreeFile(qfile); + +done: + pgss->extent = 0; + /* This counts as a query text garbage collection for our purposes */ + record_gc_qtexts(); + +release_lock: + LWLockRelease(pgss->lock); +} + +/* + * AppendJumble: Append a value that is substantive in a given query to + * the current jumble. + */ +static void +AppendJumble(pgssJumbleState *jstate, const unsigned char *item, Size size) +{ + unsigned char *jumble = jstate->jumble; + Size jumble_len = jstate->jumble_len; + + /* + * Whenever the jumble buffer is full, we hash the current contents and + * reset the buffer to contain just that hash value, thus relying on the + * hash to summarize everything so far. + */ + while (size > 0) + { + Size part_size; + + if (jumble_len >= JUMBLE_SIZE) + { + uint64 start_hash; + + start_hash = DatumGetUInt64(hash_any_extended(jumble, + JUMBLE_SIZE, 0)); + memcpy(jumble, &start_hash, sizeof(start_hash)); + jumble_len = sizeof(start_hash); + } + part_size = Min(size, JUMBLE_SIZE - jumble_len); + memcpy(jumble + jumble_len, item, part_size); + jumble_len += part_size; + item += part_size; + size -= part_size; + } + jstate->jumble_len = jumble_len; +} + +/* + * Wrappers around AppendJumble to encapsulate details of serialization + * of individual local variable elements. + */ +#define APP_JUMB(item) \ + AppendJumble(jstate, (const unsigned char *) &(item), sizeof(item)) +#define APP_JUMB_STRING(str) \ + AppendJumble(jstate, (const unsigned char *) (str), strlen(str) + 1) + +/* + * JumbleQuery: Selectively serialize the query tree, appending significant + * data to the "query jumble" while ignoring nonsignificant data. + * + * Rule of thumb for what to include is that we should ignore anything not + * semantically significant (such as alias names) as well as anything that can + * be deduced from child nodes (else we'd just be double-hashing that piece + * of information). + */ +static void +JumbleQuery(pgssJumbleState *jstate, Query *query) +{ + Assert(IsA(query, Query)); + Assert(query->utilityStmt == NULL); + + APP_JUMB(query->commandType); + /* resultRelation is usually predictable from commandType */ + JumbleExpr(jstate, (Node *) query->cteList); + JumbleRangeTable(jstate, query->rtable); + JumbleExpr(jstate, (Node *) query->jointree); + JumbleExpr(jstate, (Node *) query->targetList); + JumbleExpr(jstate, (Node *) query->onConflict); + JumbleExpr(jstate, (Node *) query->returningList); + JumbleExpr(jstate, (Node *) query->groupClause); + JumbleExpr(jstate, (Node *) query->groupingSets); + JumbleExpr(jstate, query->havingQual); + JumbleExpr(jstate, (Node *) query->windowClause); + JumbleExpr(jstate, (Node *) query->distinctClause); + JumbleExpr(jstate, (Node *) query->sortClause); + JumbleExpr(jstate, query->limitOffset); + JumbleExpr(jstate, query->limitCount); + JumbleRowMarks(jstate, query->rowMarks); + JumbleExpr(jstate, query->setOperations); +} + +/* + * Jumble a range table + */ +static void +JumbleRangeTable(pgssJumbleState *jstate, List *rtable) +{ + ListCell *lc; + + foreach(lc, rtable) + { + RangeTblEntry *rte = lfirst_node(RangeTblEntry, lc); + + APP_JUMB(rte->rtekind); + switch (rte->rtekind) + { + case RTE_RELATION: + APP_JUMB(rte->relid); + JumbleExpr(jstate, (Node *) rte->tablesample); + break; + case RTE_SUBQUERY: + JumbleQuery(jstate, rte->subquery); + break; + case RTE_JOIN: + APP_JUMB(rte->jointype); + break; + case RTE_FUNCTION: + JumbleExpr(jstate, (Node *) rte->functions); + break; + case RTE_TABLEFUNC: + JumbleExpr(jstate, (Node *) rte->tablefunc); + break; + case RTE_VALUES: + JumbleExpr(jstate, (Node *) rte->values_lists); + break; + case RTE_CTE: + + /* + * Depending on the CTE name here isn't ideal, but it's the + * only info we have to identify the referenced WITH item. + */ + APP_JUMB_STRING(rte->ctename); + APP_JUMB(rte->ctelevelsup); + break; + case RTE_NAMEDTUPLESTORE: + APP_JUMB_STRING(rte->enrname); + break; + case RTE_RESULT: + break; + default: + elog(ERROR, "unrecognized RTE kind: %d", (int) rte->rtekind); + break; + } + } +} + +/* + * Jumble a rowMarks list + */ +static void +JumbleRowMarks(pgssJumbleState *jstate, List *rowMarks) +{ + ListCell *lc; + + foreach(lc, rowMarks) + { + RowMarkClause *rowmark = lfirst_node(RowMarkClause, lc); + + if (!rowmark->pushedDown) + { + APP_JUMB(rowmark->rti); + APP_JUMB(rowmark->strength); + APP_JUMB(rowmark->waitPolicy); + } + } +} + +/* + * Jumble an expression tree + * + * In general this function should handle all the same node types that + * expression_tree_walker() does, and therefore it's coded to be as parallel + * to that function as possible. However, since we are only invoked on + * queries immediately post-parse-analysis, we need not handle node types + * that only appear in planning. + * + * Note: the reason we don't simply use expression_tree_walker() is that the + * point of that function is to support tree walkers that don't care about + * most tree node types, but here we care about all types. We should complain + * about any unrecognized node type. + */ +static void +JumbleExpr(pgssJumbleState *jstate, Node *node) +{ + ListCell *temp; + + if (node == NULL) + return; + + /* Guard against stack overflow due to overly complex expressions */ + check_stack_depth(); + + /* + * We always emit the node's NodeTag, then any additional fields that are + * considered significant, and then we recurse to any child nodes. + */ + APP_JUMB(node->type); + + switch (nodeTag(node)) + { + case T_Var: + { + Var *var = (Var *) node; + + APP_JUMB(var->varno); + APP_JUMB(var->varattno); + APP_JUMB(var->varlevelsup); + } + break; + case T_Const: + { + Const *c = (Const *) node; + + /* We jumble only the constant's type, not its value */ + APP_JUMB(c->consttype); + /* Also, record its parse location for query normalization */ + RecordConstLocation(jstate, c->location); + } + break; + case T_Param: + { + Param *p = (Param *) node; + + APP_JUMB(p->paramkind); + APP_JUMB(p->paramid); + APP_JUMB(p->paramtype); + /* Also, track the highest external Param id */ + if (p->paramkind == PARAM_EXTERN && + p->paramid > jstate->highest_extern_param_id) + jstate->highest_extern_param_id = p->paramid; + } + break; + case T_Aggref: + { + Aggref *expr = (Aggref *) node; + + APP_JUMB(expr->aggfnoid); + JumbleExpr(jstate, (Node *) expr->aggdirectargs); + JumbleExpr(jstate, (Node *) expr->args); + JumbleExpr(jstate, (Node *) expr->aggorder); + JumbleExpr(jstate, (Node *) expr->aggdistinct); + JumbleExpr(jstate, (Node *) expr->aggfilter); + } + break; + case T_GroupingFunc: + { + GroupingFunc *grpnode = (GroupingFunc *) node; + + JumbleExpr(jstate, (Node *) grpnode->refs); + } + break; + case T_WindowFunc: + { + WindowFunc *expr = (WindowFunc *) node; + + APP_JUMB(expr->winfnoid); + APP_JUMB(expr->winref); + JumbleExpr(jstate, (Node *) expr->args); + JumbleExpr(jstate, (Node *) expr->aggfilter); + } + break; + case T_SubscriptingRef: + { + SubscriptingRef *sbsref = (SubscriptingRef *) node; + + JumbleExpr(jstate, (Node *) sbsref->refupperindexpr); + JumbleExpr(jstate, (Node *) sbsref->reflowerindexpr); + JumbleExpr(jstate, (Node *) sbsref->refexpr); + JumbleExpr(jstate, (Node *) sbsref->refassgnexpr); + } + break; + case T_FuncExpr: + { + FuncExpr *expr = (FuncExpr *) node; + + APP_JUMB(expr->funcid); + JumbleExpr(jstate, (Node *) expr->args); + } + break; + case T_NamedArgExpr: + { + NamedArgExpr *nae = (NamedArgExpr *) node; + + APP_JUMB(nae->argnumber); + JumbleExpr(jstate, (Node *) nae->arg); + } + break; + case T_OpExpr: + case T_DistinctExpr: /* struct-equivalent to OpExpr */ + case T_NullIfExpr: /* struct-equivalent to OpExpr */ + { + OpExpr *expr = (OpExpr *) node; + + APP_JUMB(expr->opno); + JumbleExpr(jstate, (Node *) expr->args); + } + break; + case T_ScalarArrayOpExpr: + { + ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node; + + APP_JUMB(expr->opno); + APP_JUMB(expr->useOr); + JumbleExpr(jstate, (Node *) expr->args); + } + break; + case T_BoolExpr: + { + BoolExpr *expr = (BoolExpr *) node; + + APP_JUMB(expr->boolop); + JumbleExpr(jstate, (Node *) expr->args); + } + break; + case T_SubLink: + { + SubLink *sublink = (SubLink *) node; + + APP_JUMB(sublink->subLinkType); + APP_JUMB(sublink->subLinkId); + JumbleExpr(jstate, (Node *) sublink->testexpr); + JumbleQuery(jstate, castNode(Query, sublink->subselect)); + } + break; + case T_FieldSelect: + { + FieldSelect *fs = (FieldSelect *) node; + + APP_JUMB(fs->fieldnum); + JumbleExpr(jstate, (Node *) fs->arg); + } + break; + case T_FieldStore: + { + FieldStore *fstore = (FieldStore *) node; + + JumbleExpr(jstate, (Node *) fstore->arg); + JumbleExpr(jstate, (Node *) fstore->newvals); + } + break; + case T_RelabelType: + { + RelabelType *rt = (RelabelType *) node; + + APP_JUMB(rt->resulttype); + JumbleExpr(jstate, (Node *) rt->arg); + } + break; + case T_CoerceViaIO: + { + CoerceViaIO *cio = (CoerceViaIO *) node; + + APP_JUMB(cio->resulttype); + JumbleExpr(jstate, (Node *) cio->arg); + } + break; + case T_ArrayCoerceExpr: + { + ArrayCoerceExpr *acexpr = (ArrayCoerceExpr *) node; + + APP_JUMB(acexpr->resulttype); + JumbleExpr(jstate, (Node *) acexpr->arg); + JumbleExpr(jstate, (Node *) acexpr->elemexpr); + } + break; + case T_ConvertRowtypeExpr: + { + ConvertRowtypeExpr *crexpr = (ConvertRowtypeExpr *) node; + + APP_JUMB(crexpr->resulttype); + JumbleExpr(jstate, (Node *) crexpr->arg); + } + break; + case T_CollateExpr: + { + CollateExpr *ce = (CollateExpr *) node; + + APP_JUMB(ce->collOid); + JumbleExpr(jstate, (Node *) ce->arg); + } + break; + case T_CaseExpr: + { + CaseExpr *caseexpr = (CaseExpr *) node; + + JumbleExpr(jstate, (Node *) caseexpr->arg); + foreach(temp, caseexpr->args) + { + CaseWhen *when = lfirst_node(CaseWhen, temp); + + JumbleExpr(jstate, (Node *) when->expr); + JumbleExpr(jstate, (Node *) when->result); + } + JumbleExpr(jstate, (Node *) caseexpr->defresult); + } + break; + case T_CaseTestExpr: + { + CaseTestExpr *ct = (CaseTestExpr *) node; + + APP_JUMB(ct->typeId); + } + break; + case T_ArrayExpr: + JumbleExpr(jstate, (Node *) ((ArrayExpr *) node)->elements); + break; + case T_RowExpr: + JumbleExpr(jstate, (Node *) ((RowExpr *) node)->args); + break; + case T_RowCompareExpr: + { + RowCompareExpr *rcexpr = (RowCompareExpr *) node; + + APP_JUMB(rcexpr->rctype); + JumbleExpr(jstate, (Node *) rcexpr->largs); + JumbleExpr(jstate, (Node *) rcexpr->rargs); + } + break; + case T_CoalesceExpr: + JumbleExpr(jstate, (Node *) ((CoalesceExpr *) node)->args); + break; + case T_MinMaxExpr: + { + MinMaxExpr *mmexpr = (MinMaxExpr *) node; + + APP_JUMB(mmexpr->op); + JumbleExpr(jstate, (Node *) mmexpr->args); + } + break; + case T_SQLValueFunction: + { + SQLValueFunction *svf = (SQLValueFunction *) node; + + APP_JUMB(svf->op); + /* type is fully determined by op */ + APP_JUMB(svf->typmod); + } + break; + case T_XmlExpr: + { + XmlExpr *xexpr = (XmlExpr *) node; + + APP_JUMB(xexpr->op); + JumbleExpr(jstate, (Node *) xexpr->named_args); + JumbleExpr(jstate, (Node *) xexpr->args); + } + break; + case T_NullTest: + { + NullTest *nt = (NullTest *) node; + + APP_JUMB(nt->nulltesttype); + JumbleExpr(jstate, (Node *) nt->arg); + } + break; + case T_BooleanTest: + { + BooleanTest *bt = (BooleanTest *) node; + + APP_JUMB(bt->booltesttype); + JumbleExpr(jstate, (Node *) bt->arg); + } + break; + case T_CoerceToDomain: + { + CoerceToDomain *cd = (CoerceToDomain *) node; + + APP_JUMB(cd->resulttype); + JumbleExpr(jstate, (Node *) cd->arg); + } + break; + case T_CoerceToDomainValue: + { + CoerceToDomainValue *cdv = (CoerceToDomainValue *) node; + + APP_JUMB(cdv->typeId); + } + break; + case T_SetToDefault: + { + SetToDefault *sd = (SetToDefault *) node; + + APP_JUMB(sd->typeId); + } + break; + case T_CurrentOfExpr: + { + CurrentOfExpr *ce = (CurrentOfExpr *) node; + + APP_JUMB(ce->cvarno); + if (ce->cursor_name) + APP_JUMB_STRING(ce->cursor_name); + APP_JUMB(ce->cursor_param); + } + break; + case T_NextValueExpr: + { + NextValueExpr *nve = (NextValueExpr *) node; + + APP_JUMB(nve->seqid); + APP_JUMB(nve->typeId); + } + break; + case T_InferenceElem: + { + InferenceElem *ie = (InferenceElem *) node; + + APP_JUMB(ie->infercollid); + APP_JUMB(ie->inferopclass); + JumbleExpr(jstate, ie->expr); + } + break; + case T_TargetEntry: + { + TargetEntry *tle = (TargetEntry *) node; + + APP_JUMB(tle->resno); + APP_JUMB(tle->ressortgroupref); + JumbleExpr(jstate, (Node *) tle->expr); + } + break; + case T_RangeTblRef: + { + RangeTblRef *rtr = (RangeTblRef *) node; + + APP_JUMB(rtr->rtindex); + } + break; + case T_JoinExpr: + { + JoinExpr *join = (JoinExpr *) node; + + APP_JUMB(join->jointype); + APP_JUMB(join->isNatural); + APP_JUMB(join->rtindex); + JumbleExpr(jstate, join->larg); + JumbleExpr(jstate, join->rarg); + JumbleExpr(jstate, join->quals); + } + break; + case T_FromExpr: + { + FromExpr *from = (FromExpr *) node; + + JumbleExpr(jstate, (Node *) from->fromlist); + JumbleExpr(jstate, from->quals); + } + break; + case T_OnConflictExpr: + { + OnConflictExpr *conf = (OnConflictExpr *) node; + + APP_JUMB(conf->action); + JumbleExpr(jstate, (Node *) conf->arbiterElems); + JumbleExpr(jstate, conf->arbiterWhere); + JumbleExpr(jstate, (Node *) conf->onConflictSet); + JumbleExpr(jstate, conf->onConflictWhere); + APP_JUMB(conf->constraint); + APP_JUMB(conf->exclRelIndex); + JumbleExpr(jstate, (Node *) conf->exclRelTlist); + } + break; + case T_List: + foreach(temp, (List *) node) + { + JumbleExpr(jstate, (Node *) lfirst(temp)); + } + break; + case T_IntList: + foreach(temp, (List *) node) + { + APP_JUMB(lfirst_int(temp)); + } + break; + case T_SortGroupClause: + { + SortGroupClause *sgc = (SortGroupClause *) node; + + APP_JUMB(sgc->tleSortGroupRef); + APP_JUMB(sgc->eqop); + APP_JUMB(sgc->sortop); + APP_JUMB(sgc->nulls_first); + } + break; + case T_GroupingSet: + { + GroupingSet *gsnode = (GroupingSet *) node; + + JumbleExpr(jstate, (Node *) gsnode->content); + } + break; + case T_WindowClause: + { + WindowClause *wc = (WindowClause *) node; + + APP_JUMB(wc->winref); + APP_JUMB(wc->frameOptions); + JumbleExpr(jstate, (Node *) wc->partitionClause); + JumbleExpr(jstate, (Node *) wc->orderClause); + JumbleExpr(jstate, wc->startOffset); + JumbleExpr(jstate, wc->endOffset); + } + break; + case T_CommonTableExpr: + { + CommonTableExpr *cte = (CommonTableExpr *) node; + + /* we store the string name because RTE_CTE RTEs need it */ + APP_JUMB_STRING(cte->ctename); + APP_JUMB(cte->ctematerialized); + JumbleQuery(jstate, castNode(Query, cte->ctequery)); + } + break; + case T_SetOperationStmt: + { + SetOperationStmt *setop = (SetOperationStmt *) node; + + APP_JUMB(setop->op); + APP_JUMB(setop->all); + JumbleExpr(jstate, setop->larg); + JumbleExpr(jstate, setop->rarg); + } + break; + case T_RangeTblFunction: + { + RangeTblFunction *rtfunc = (RangeTblFunction *) node; + + JumbleExpr(jstate, rtfunc->funcexpr); + } + break; + case T_TableFunc: + { + TableFunc *tablefunc = (TableFunc *) node; + + JumbleExpr(jstate, tablefunc->docexpr); + JumbleExpr(jstate, tablefunc->rowexpr); + JumbleExpr(jstate, (Node *) tablefunc->colexprs); + } + break; + case T_TableSampleClause: + { + TableSampleClause *tsc = (TableSampleClause *) node; + + APP_JUMB(tsc->tsmhandler); + JumbleExpr(jstate, (Node *) tsc->args); + JumbleExpr(jstate, (Node *) tsc->repeatable); + } + break; + default: + /* Only a warning, since we can stumble along anyway */ + elog(WARNING, "unrecognized node type: %d", + (int) nodeTag(node)); + break; + } +} + +/* + * Record location of constant within query string of query tree + * that is currently being walked. + */ +static void +RecordConstLocation(pgssJumbleState *jstate, int location) +{ + /* -1 indicates unknown or undefined location */ + if (location >= 0) + { + /* enlarge array if needed */ + if (jstate->clocations_count >= jstate->clocations_buf_size) + { + jstate->clocations_buf_size *= 2; + jstate->clocations = (pgssLocationLen *) + repalloc(jstate->clocations, + jstate->clocations_buf_size * + sizeof(pgssLocationLen)); + } + jstate->clocations[jstate->clocations_count].location = location; + /* initialize lengths to -1 to simplify fill_in_constant_lengths */ + jstate->clocations[jstate->clocations_count].length = -1; + jstate->clocations_count++; + } +} + +/* + * Generate a normalized version of the query string that will be used to + * represent all similar queries. + * + * Note that the normalized representation may well vary depending on + * just which "equivalent" query is used to create the hashtable entry. + * We assume this is OK. + * + * If query_loc > 0, then "query" has been advanced by that much compared to + * the original string start, so we need to translate the provided locations + * to compensate. (This lets us avoid re-scanning statements before the one + * of interest, so it's worth doing.) + * + * *query_len_p contains the input string length, and is updated with + * the result string length on exit. The resulting string might be longer + * or shorter depending on what happens with replacement of constants. + * + * Returns a palloc'd string. + */ +static char * +generate_normalized_query(pgssJumbleState *jstate, const char *query, + int query_loc, int *query_len_p, int encoding) +{ + char *norm_query; + int query_len = *query_len_p; + int i, + norm_query_buflen, /* Space allowed for norm_query */ + len_to_wrt, /* Length (in bytes) to write */ + quer_loc = 0, /* Source query byte location */ + n_quer_loc = 0, /* Normalized query byte location */ + last_off = 0, /* Offset from start for previous tok */ + last_tok_len = 0; /* Length (in bytes) of that tok */ + + /* + * Get constants' lengths (core system only gives us locations). Note + * this also ensures the items are sorted by location. + */ + fill_in_constant_lengths(jstate, query, query_loc); + + /* + * Allow for $n symbols to be longer than the constants they replace. + * Constants must take at least one byte in text form, while a $n symbol + * certainly isn't more than 11 bytes, even if n reaches INT_MAX. We + * could refine that limit based on the max value of n for the current + * query, but it hardly seems worth any extra effort to do so. + */ + norm_query_buflen = query_len + jstate->clocations_count * 10; + + /* Allocate result buffer */ + norm_query = palloc(norm_query_buflen + 1); + + for (i = 0; i < jstate->clocations_count; i++) + { + int off, /* Offset from start for cur tok */ + tok_len; /* Length (in bytes) of that tok */ + + off = jstate->clocations[i].location; + /* Adjust recorded location if we're dealing with partial string */ + off -= query_loc; + + tok_len = jstate->clocations[i].length; + + if (tok_len < 0) + continue; /* ignore any duplicates */ + + /* Copy next chunk (what precedes the next constant) */ + len_to_wrt = off - last_off; + len_to_wrt -= last_tok_len; + + Assert(len_to_wrt >= 0); + memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt); + n_quer_loc += len_to_wrt; + + /* And insert a param symbol in place of the constant token */ + n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d", + i + 1 + jstate->highest_extern_param_id); + + quer_loc = off + tok_len; + last_off = off; + last_tok_len = tok_len; + } + + /* + * We've copied up until the last ignorable constant. Copy over the + * remaining bytes of the original query string. + */ + len_to_wrt = query_len - quer_loc; + + Assert(len_to_wrt >= 0); + memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt); + n_quer_loc += len_to_wrt; + + Assert(n_quer_loc <= norm_query_buflen); + norm_query[n_quer_loc] = '\0'; + + *query_len_p = n_quer_loc; + return norm_query; +} + +/* + * Given a valid SQL string and an array of constant-location records, + * fill in the textual lengths of those constants. + * + * The constants may use any allowed constant syntax, such as float literals, + * bit-strings, single-quoted strings and dollar-quoted strings. This is + * accomplished by using the public API for the core scanner. + * + * It is the caller's job to ensure that the string is a valid SQL statement + * with constants at the indicated locations. Since in practice the string + * has already been parsed, and the locations that the caller provides will + * have originated from within the authoritative parser, this should not be + * a problem. + * + * Duplicate constant pointers are possible, and will have their lengths + * marked as '-1', so that they are later ignored. (Actually, we assume the + * lengths were initialized as -1 to start with, and don't change them here.) + * + * If query_loc > 0, then "query" has been advanced by that much compared to + * the original string start, so we need to translate the provided locations + * to compensate. (This lets us avoid re-scanning statements before the one + * of interest, so it's worth doing.) + * + * N.B. There is an assumption that a '-' character at a Const location begins + * a negative numeric constant. This precludes there ever being another + * reason for a constant to start with a '-'. + */ +static void +fill_in_constant_lengths(pgssJumbleState *jstate, const char *query, + int query_loc) +{ + pgssLocationLen *locs; + core_yyscan_t yyscanner; + core_yy_extra_type yyextra; + core_YYSTYPE yylval; + YYLTYPE yylloc; + int last_loc = -1; + int i; + + /* + * Sort the records by location so that we can process them in order while + * scanning the query text. + */ + if (jstate->clocations_count > 1) + qsort(jstate->clocations, jstate->clocations_count, + sizeof(pgssLocationLen), comp_location); + locs = jstate->clocations; + + /* initialize the flex scanner --- should match raw_parser() */ + yyscanner = scanner_init(query, + &yyextra, + &ScanKeywords, + ScanKeywordTokens); + + /* we don't want to re-emit any escape string warnings */ + yyextra.escape_string_warning = false; + + /* Search for each constant, in sequence */ + for (i = 0; i < jstate->clocations_count; i++) + { + int loc = locs[i].location; + int tok; + + /* Adjust recorded location if we're dealing with partial string */ + loc -= query_loc; + + Assert(loc >= 0); + + if (loc <= last_loc) + continue; /* Duplicate constant, ignore */ + + /* Lex tokens until we find the desired constant */ + for (;;) + { + tok = core_yylex(&yylval, &yylloc, yyscanner); + + /* We should not hit end-of-string, but if we do, behave sanely */ + if (tok == 0) + break; /* out of inner for-loop */ + + /* + * We should find the token position exactly, but if we somehow + * run past it, work with that. + */ + if (yylloc >= loc) + { + if (query[loc] == '-') + { + /* + * It's a negative value - this is the one and only case + * where we replace more than a single token. + * + * Do not compensate for the core system's special-case + * adjustment of location to that of the leading '-' + * operator in the event of a negative constant. It is + * also useful for our purposes to start from the minus + * symbol. In this way, queries like "select * from foo + * where bar = 1" and "select * from foo where bar = -2" + * will have identical normalized query strings. + */ + tok = core_yylex(&yylval, &yylloc, yyscanner); + if (tok == 0) + break; /* out of inner for-loop */ + } + + /* + * We now rely on the assumption that flex has placed a zero + * byte after the text of the current token in scanbuf. + */ + locs[i].length = strlen(yyextra.scanbuf + loc); + break; /* out of inner for-loop */ + } + } + + /* If we hit end-of-string, give up, leaving remaining lengths -1 */ + if (tok == 0) + break; + + last_loc = loc; + } + + scanner_finish(yyscanner); +} + +/* + * comp_location: comparator for qsorting pgssLocationLen structs by location + */ +static int +comp_location(const void *a, const void *b) +{ + int l = ((const pgssLocationLen *) a)->location; + int r = ((const pgssLocationLen *) b)->location; + + if (l < r) + return -1; + else if (l > r) + return +1; + else + return 0; +} |