diff options
Diffstat (limited to 'ext/misc/stmt.c')
| -rw-r--r-- | ext/misc/stmt.c | 337 |
1 files changed, 337 insertions, 0 deletions
diff --git a/ext/misc/stmt.c b/ext/misc/stmt.c new file mode 100644 index 0000000..1687f41 --- /dev/null +++ b/ext/misc/stmt.c @@ -0,0 +1,337 @@ +/* +** 2017-05-31 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** +** This file demonstrates an eponymous virtual table that returns information +** about all prepared statements for the database connection. +** +** Usage example: +** +** .load ./stmt +** .mode line +** .header on +** SELECT * FROM stmt; +*/ +#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_STMTVTAB) +#if !defined(SQLITEINT_H) +#include "sqlite3ext.h" +#endif +SQLITE_EXTENSION_INIT1 +#include <assert.h> +#include <string.h> + +#ifndef SQLITE_OMIT_VIRTUALTABLE + + +#define STMT_NUM_INTEGER_COLUMN 10 +typedef struct StmtRow StmtRow; +struct StmtRow { + sqlite3_int64 iRowid; /* Rowid value */ + char *zSql; /* column "sql" */ + int aCol[STMT_NUM_INTEGER_COLUMN+1]; /* all other column values */ + StmtRow *pNext; /* Next row to return */ +}; + +/* stmt_vtab is a subclass of sqlite3_vtab which will +** serve as the underlying representation of a stmt virtual table +*/ +typedef struct stmt_vtab stmt_vtab; +struct stmt_vtab { + sqlite3_vtab base; /* Base class - must be first */ + sqlite3 *db; /* Database connection for this stmt vtab */ +}; + +/* stmt_cursor is a subclass of sqlite3_vtab_cursor which will +** serve as the underlying representation of a cursor that scans +** over rows of the result +*/ +typedef struct stmt_cursor stmt_cursor; +struct stmt_cursor { + sqlite3_vtab_cursor base; /* Base class - must be first */ + sqlite3 *db; /* Database connection for this cursor */ + StmtRow *pRow; /* Current row */ +}; + +/* +** The stmtConnect() method is invoked to create a new +** stmt_vtab that describes the stmt virtual table. +** +** Think of this routine as the constructor for stmt_vtab objects. +** +** All this routine needs to do is: +** +** (1) Allocate the stmt_vtab object and initialize all fields. +** +** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the +** result set of queries against stmt will look like. +*/ +static int stmtConnect( + sqlite3 *db, + void *pAux, + int argc, const char *const*argv, + sqlite3_vtab **ppVtab, + char **pzErr +){ + stmt_vtab *pNew; + int rc; + +/* Column numbers */ +#define STMT_COLUMN_SQL 0 /* SQL for the statement */ +#define STMT_COLUMN_NCOL 1 /* Number of result columns */ +#define STMT_COLUMN_RO 2 /* True if read-only */ +#define STMT_COLUMN_BUSY 3 /* True if currently busy */ +#define STMT_COLUMN_NSCAN 4 /* SQLITE_STMTSTATUS_FULLSCAN_STEP */ +#define STMT_COLUMN_NSORT 5 /* SQLITE_STMTSTATUS_SORT */ +#define STMT_COLUMN_NAIDX 6 /* SQLITE_STMTSTATUS_AUTOINDEX */ +#define STMT_COLUMN_NSTEP 7 /* SQLITE_STMTSTATUS_VM_STEP */ +#define STMT_COLUMN_REPREP 8 /* SQLITE_STMTSTATUS_REPREPARE */ +#define STMT_COLUMN_RUN 9 /* SQLITE_STMTSTATUS_RUN */ +#define STMT_COLUMN_MEM 10 /* SQLITE_STMTSTATUS_MEMUSED */ + + + rc = sqlite3_declare_vtab(db, + "CREATE TABLE x(sql,ncol,ro,busy,nscan,nsort,naidx,nstep," + "reprep,run,mem)"); + if( rc==SQLITE_OK ){ + pNew = sqlite3_malloc64( sizeof(*pNew) ); + *ppVtab = (sqlite3_vtab*)pNew; + if( pNew==0 ) return SQLITE_NOMEM; + memset(pNew, 0, sizeof(*pNew)); + pNew->db = db; + } + return rc; +} + +/* +** This method is the destructor for stmt_cursor objects. +*/ +static int stmtDisconnect(sqlite3_vtab *pVtab){ + sqlite3_free(pVtab); + return SQLITE_OK; +} + +/* +** Constructor for a new stmt_cursor object. +*/ +static int stmtOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){ + stmt_cursor *pCur; + pCur = sqlite3_malloc64( sizeof(*pCur) ); + if( pCur==0 ) return SQLITE_NOMEM; + memset(pCur, 0, sizeof(*pCur)); + pCur->db = ((stmt_vtab*)p)->db; + *ppCursor = &pCur->base; + return SQLITE_OK; +} + +static void stmtCsrReset(stmt_cursor *pCur){ + StmtRow *pRow = 0; + StmtRow *pNext = 0; + for(pRow=pCur->pRow; pRow; pRow=pNext){ + pNext = pRow->pNext; + sqlite3_free(pRow); + } + pCur->pRow = 0; +} + +/* +** Destructor for a stmt_cursor. +*/ +static int stmtClose(sqlite3_vtab_cursor *cur){ + stmtCsrReset((stmt_cursor*)cur); + sqlite3_free(cur); + return SQLITE_OK; +} + + +/* +** Advance a stmt_cursor to its next row of output. +*/ +static int stmtNext(sqlite3_vtab_cursor *cur){ + stmt_cursor *pCur = (stmt_cursor*)cur; + StmtRow *pNext = pCur->pRow->pNext; + sqlite3_free(pCur->pRow); + pCur->pRow = pNext; + return SQLITE_OK; +} + +/* +** Return values of columns for the row at which the stmt_cursor +** is currently pointing. +*/ +static int stmtColumn( + sqlite3_vtab_cursor *cur, /* The cursor */ + sqlite3_context *ctx, /* First argument to sqlite3_result_...() */ + int i /* Which column to return */ +){ + stmt_cursor *pCur = (stmt_cursor*)cur; + StmtRow *pRow = pCur->pRow; + if( i==STMT_COLUMN_SQL ){ + sqlite3_result_text(ctx, pRow->zSql, -1, SQLITE_TRANSIENT); + }else{ + sqlite3_result_int(ctx, pRow->aCol[i]); + } + return SQLITE_OK; +} + +/* +** Return the rowid for the current row. In this implementation, the +** rowid is the same as the output value. +*/ +static int stmtRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){ + stmt_cursor *pCur = (stmt_cursor*)cur; + *pRowid = pCur->pRow->iRowid; + return SQLITE_OK; +} + +/* +** Return TRUE if the cursor has been moved off of the last +** row of output. +*/ +static int stmtEof(sqlite3_vtab_cursor *cur){ + stmt_cursor *pCur = (stmt_cursor*)cur; + return pCur->pRow==0; +} + +/* +** This method is called to "rewind" the stmt_cursor object back +** to the first row of output. This method is always called at least +** once prior to any call to stmtColumn() or stmtRowid() or +** stmtEof(). +*/ +static int stmtFilter( + sqlite3_vtab_cursor *pVtabCursor, + int idxNum, const char *idxStr, + int argc, sqlite3_value **argv +){ + stmt_cursor *pCur = (stmt_cursor *)pVtabCursor; + sqlite3_stmt *p = 0; + sqlite3_int64 iRowid = 1; + StmtRow **ppRow = 0; + + stmtCsrReset(pCur); + ppRow = &pCur->pRow; + for(p=sqlite3_next_stmt(pCur->db, 0); p; p=sqlite3_next_stmt(pCur->db, p)){ + const char *zSql = sqlite3_sql(p); + sqlite3_int64 nSql = zSql ? strlen(zSql)+1 : 0; + StmtRow *pNew = (StmtRow*)sqlite3_malloc64(sizeof(StmtRow) + nSql); + + if( pNew==0 ) return SQLITE_NOMEM; + memset(pNew, 0, sizeof(StmtRow)); + if( zSql ){ + pNew->zSql = (char*)&pNew[1]; + memcpy(pNew->zSql, zSql, nSql); + } + pNew->aCol[STMT_COLUMN_NCOL] = sqlite3_column_count(p); + pNew->aCol[STMT_COLUMN_RO] = sqlite3_stmt_readonly(p); + pNew->aCol[STMT_COLUMN_BUSY] = sqlite3_stmt_busy(p); + pNew->aCol[STMT_COLUMN_NSCAN] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_FULLSCAN_STEP, 0 + ); + pNew->aCol[STMT_COLUMN_NSORT] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_SORT, 0 + ); + pNew->aCol[STMT_COLUMN_NAIDX] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_AUTOINDEX, 0 + ); + pNew->aCol[STMT_COLUMN_NSTEP] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_VM_STEP, 0 + ); + pNew->aCol[STMT_COLUMN_REPREP] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_REPREPARE, 0 + ); + pNew->aCol[STMT_COLUMN_RUN] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_RUN, 0 + ); + pNew->aCol[STMT_COLUMN_MEM] = sqlite3_stmt_status( + p, SQLITE_STMTSTATUS_MEMUSED, 0 + ); + pNew->iRowid = iRowid++; + *ppRow = pNew; + ppRow = &pNew->pNext; + } + + return SQLITE_OK; +} + +/* +** SQLite will invoke this method one or more times while planning a query +** that uses the stmt virtual table. This routine needs to create +** a query plan for each invocation and compute an estimated cost for that +** plan. +*/ +static int stmtBestIndex( + sqlite3_vtab *tab, + sqlite3_index_info *pIdxInfo +){ + pIdxInfo->estimatedCost = (double)500; + pIdxInfo->estimatedRows = 500; + return SQLITE_OK; +} + +/* +** This following structure defines all the methods for the +** stmt virtual table. +*/ +static sqlite3_module stmtModule = { + 0, /* iVersion */ + 0, /* xCreate */ + stmtConnect, /* xConnect */ + stmtBestIndex, /* xBestIndex */ + stmtDisconnect, /* xDisconnect */ + 0, /* xDestroy */ + stmtOpen, /* xOpen - open a cursor */ + stmtClose, /* xClose - close a cursor */ + stmtFilter, /* xFilter - configure scan constraints */ + stmtNext, /* xNext - advance a cursor */ + stmtEof, /* xEof - check for end of scan */ + stmtColumn, /* xColumn - read data */ + stmtRowid, /* xRowid - read data */ + 0, /* xUpdate */ + 0, /* xBegin */ + 0, /* xSync */ + 0, /* xCommit */ + 0, /* xRollback */ + 0, /* xFindMethod */ + 0, /* xRename */ + 0, /* xSavepoint */ + 0, /* xRelease */ + 0, /* xRollbackTo */ + 0, /* xShadowName */ +}; + +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + +int sqlite3StmtVtabInit(sqlite3 *db){ + int rc = SQLITE_OK; +#ifndef SQLITE_OMIT_VIRTUALTABLE + rc = sqlite3_create_module(db, "sqlite_stmt", &stmtModule, 0); +#endif + return rc; +} + +#ifndef SQLITE_CORE +#ifdef _WIN32 +__declspec(dllexport) +#endif +int sqlite3_stmt_init( + sqlite3 *db, + char **pzErrMsg, + const sqlite3_api_routines *pApi +){ + int rc = SQLITE_OK; + SQLITE_EXTENSION_INIT2(pApi); +#ifndef SQLITE_OMIT_VIRTUALTABLE + rc = sqlite3StmtVtabInit(db); +#endif + return rc; +} +#endif /* SQLITE_CORE */ +#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_STMTVTAB) */ |