diff options
Diffstat (limited to 'contrib/pg_prewarm/pg_prewarm.c')
| -rw-r--r-- | contrib/pg_prewarm/pg_prewarm.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/contrib/pg_prewarm/pg_prewarm.c b/contrib/pg_prewarm/pg_prewarm.c new file mode 100644 index 0000000..48d0132 --- /dev/null +++ b/contrib/pg_prewarm/pg_prewarm.c @@ -0,0 +1,205 @@ +/*------------------------------------------------------------------------- + * + * pg_prewarm.c + * prewarming utilities + * + * Copyright (c) 2010-2021, PostgreSQL Global Development Group + * + * IDENTIFICATION + * contrib/pg_prewarm/pg_prewarm.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include <sys/stat.h> +#include <unistd.h> + +#include "access/relation.h" +#include "fmgr.h" +#include "miscadmin.h" +#include "storage/bufmgr.h" +#include "storage/smgr.h" +#include "utils/acl.h" +#include "utils/builtins.h" +#include "utils/lsyscache.h" +#include "utils/rel.h" + +PG_MODULE_MAGIC; + +PG_FUNCTION_INFO_V1(pg_prewarm); + +typedef enum +{ + PREWARM_PREFETCH, + PREWARM_READ, + PREWARM_BUFFER +} PrewarmType; + +static PGAlignedBlock blockbuffer; + +/* + * pg_prewarm(regclass, mode text, fork text, + * first_block int8, last_block int8) + * + * The first argument is the relation to be prewarmed; the second controls + * how prewarming is done; legal options are 'prefetch', 'read', and 'buffer'. + * The third is the name of the relation fork to be prewarmed. The fourth + * and fifth arguments specify the first and last block to be prewarmed. + * If the fourth argument is NULL, it will be taken as 0; if the fifth argument + * is NULL, it will be taken as the number of blocks in the relation. The + * return value is the number of blocks successfully prewarmed. + */ +Datum +pg_prewarm(PG_FUNCTION_ARGS) +{ + Oid relOid; + text *forkName; + text *type; + int64 first_block; + int64 last_block; + int64 nblocks; + int64 blocks_done = 0; + int64 block; + Relation rel; + ForkNumber forkNumber; + char *forkString; + char *ttype; + PrewarmType ptype; + AclResult aclresult; + + /* Basic sanity checking. */ + if (PG_ARGISNULL(0)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("relation cannot be null"))); + relOid = PG_GETARG_OID(0); + if (PG_ARGISNULL(1)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("prewarm type cannot be null"))); + type = PG_GETARG_TEXT_PP(1); + ttype = text_to_cstring(type); + if (strcmp(ttype, "prefetch") == 0) + ptype = PREWARM_PREFETCH; + else if (strcmp(ttype, "read") == 0) + ptype = PREWARM_READ; + else if (strcmp(ttype, "buffer") == 0) + ptype = PREWARM_BUFFER; + else + { + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid prewarm type"), + errhint("Valid prewarm types are \"prefetch\", \"read\", and \"buffer\"."))); + PG_RETURN_INT64(0); /* Placate compiler. */ + } + if (PG_ARGISNULL(2)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("relation fork cannot be null"))); + forkName = PG_GETARG_TEXT_PP(2); + forkString = text_to_cstring(forkName); + forkNumber = forkname_to_number(forkString); + + /* Open relation and check privileges. */ + rel = relation_open(relOid, AccessShareLock); + aclresult = pg_class_aclcheck(relOid, GetUserId(), ACL_SELECT); + if (aclresult != ACLCHECK_OK) + aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind), get_rel_name(relOid)); + + /* Check that the fork exists. */ + RelationOpenSmgr(rel); + if (!smgrexists(rel->rd_smgr, forkNumber)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("fork \"%s\" does not exist for this relation", + forkString))); + + /* Validate block numbers, or handle nulls. */ + nblocks = RelationGetNumberOfBlocksInFork(rel, forkNumber); + if (PG_ARGISNULL(3)) + first_block = 0; + else + { + first_block = PG_GETARG_INT64(3); + if (first_block < 0 || first_block >= nblocks) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("starting block number must be between 0 and %lld", + (long long) (nblocks - 1)))); + } + if (PG_ARGISNULL(4)) + last_block = nblocks - 1; + else + { + last_block = PG_GETARG_INT64(4); + if (last_block < 0 || last_block >= nblocks) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("ending block number must be between 0 and %lld", + (long long) (nblocks - 1)))); + } + + /* Now we're ready to do the real work. */ + if (ptype == PREWARM_PREFETCH) + { +#ifdef USE_PREFETCH + + /* + * In prefetch mode, we just hint the OS to read the blocks, but we + * don't know whether it really does it, and we don't wait for it to + * finish. + * + * It would probably be better to pass our prefetch requests in chunks + * of a megabyte or maybe even a whole segment at a time, but there's + * no practical way to do that at present without a gross modularity + * violation, so we just do this. + */ + for (block = first_block; block <= last_block; ++block) + { + CHECK_FOR_INTERRUPTS(); + PrefetchBuffer(rel, forkNumber, block); + ++blocks_done; + } +#else + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("prefetch is not supported by this build"))); +#endif + } + else if (ptype == PREWARM_READ) + { + /* + * In read mode, we actually read the blocks, but not into shared + * buffers. This is more portable than prefetch mode (it works + * everywhere) and is synchronous. + */ + for (block = first_block; block <= last_block; ++block) + { + CHECK_FOR_INTERRUPTS(); + smgrread(rel->rd_smgr, forkNumber, block, blockbuffer.data); + ++blocks_done; + } + } + else if (ptype == PREWARM_BUFFER) + { + /* + * In buffer mode, we actually pull the data into shared_buffers. + */ + for (block = first_block; block <= last_block; ++block) + { + Buffer buf; + + CHECK_FOR_INTERRUPTS(); + buf = ReadBufferExtended(rel, forkNumber, block, RBM_NORMAL, NULL); + ReleaseBuffer(buf); + ++blocks_done; + } + } + + /* Close relation, release lock. */ + relation_close(rel, AccessShareLock); + + PG_RETURN_INT64(blocks_done); +} |