--- /dev/null
+/*
+** 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 ./stmts
+** .mode line
+** .header on
+** SELECT * FROM stmts;
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <assert.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** The following macros are used to cast pointers to integers.
+** The way you do this varies from one compiler
+** to the next, so we have developed the following set of #if statements
+** to generate appropriate macros for a wide range of compilers.
+*/
+#if defined(__PTRDIFF_TYPE__) /* This case should work for GCC */
+# define SQLITE_PTR_TO_INT64(X) ((sqlite3_int64)(__PTRDIFF_TYPE__)(X))
+#elif !defined(__GNUC__) /* Works for compilers other than LLVM */
+# define SQLITE_PTR_TO_INT64(X) ((sqlite3_int64)(((char*)X)-(char*)0))
+#elif defined(HAVE_STDINT_H) /* Use this case if we have ANSI headers */
+# define SQLITE_PTR_TO_INT64(X) ((sqlite3_int64)(intptr_t)(X))
+#else /* Generates a warning - but it always works */
+# define SQLITE_PTR_TO_INT64(X) ((sqlite3_int64)(X))
+#endif
+
+
+/* stmts_vtab is a subclass of sqlite3_vtab which will
+** serve as the underlying representation of a stmts virtual table
+*/
+typedef struct stmts_vtab stmts_vtab;
+struct stmts_vtab {
+ sqlite3_vtab base; /* Base class - must be first */
+ sqlite3 *db; /* Database connection for this stmts vtab */
+};
+
+/* stmts_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 stmts_cursor stmts_cursor;
+struct stmts_cursor {
+ sqlite3_vtab_cursor base; /* Base class - must be first */
+ sqlite3 *db; /* Database connection for this cursor */
+ sqlite3_stmt *pStmt; /* Statement cursor is currently pointing at */
+ sqlite3_int64 iRowid; /* The rowid */
+};
+
+/*
+** The stmtsConnect() method is invoked to create a new
+** stmts_vtab that describes the generate_stmts virtual table.
+**
+** Think of this routine as the constructor for stmts_vtab objects.
+**
+** All this routine needs to do is:
+**
+** (1) Allocate the stmts_vtab object and initialize all fields.
+**
+** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
+** result set of queries against generate_stmts will look like.
+*/
+static int stmtsConnect(
+ sqlite3 *db,
+ void *pAux,
+ int argc, const char *const*argv,
+ sqlite3_vtab **ppVtab,
+ char **pzErr
+){
+ stmts_vtab *pNew;
+ int rc;
+
+/* Column numbers */
+#define STMTS_COLUMN_PTR 0 /* Numeric value of the statement pointer */
+#define STMTS_COLUMN_SQL 1 /* SQL for the statement */
+#define STMTS_COLUMN_NCOL 2 /* Number of result columns */
+#define STMTS_COLUMN_RO 3 /* True if read-only */
+#define STMTS_COLUMN_BUSY 4 /* True if currently busy */
+#define STMTS_COLUMN_NSCAN 5 /* SQLITE_STMTSTATUS_FULLSCAN_STEP */
+#define STMTS_COLUMN_NSORT 6 /* SQLITE_STMTSTATUS_SORT */
+#define STMTS_COLUMN_NAIDX 7 /* SQLITE_STMTSTATUS_AUTOINDEX */
+#define STMTS_COLUMN_NSTEP 8 /* SQLITE_STMTSTATUS_VM_STEP */
+
+
+ rc = sqlite3_declare_vtab(db,
+ "CREATE TABLE x(ptr,sql,ncol,ro,busy,nscan,nsort,naidx,nstep)");
+ if( rc==SQLITE_OK ){
+ pNew = sqlite3_malloc( 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 stmts_cursor objects.
+*/
+static int stmtsDisconnect(sqlite3_vtab *pVtab){
+ sqlite3_free(pVtab);
+ return SQLITE_OK;
+}
+
+/*
+** Constructor for a new stmts_cursor object.
+*/
+static int stmtsOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+ stmts_cursor *pCur;
+ pCur = sqlite3_malloc( sizeof(*pCur) );
+ if( pCur==0 ) return SQLITE_NOMEM;
+ memset(pCur, 0, sizeof(*pCur));
+ pCur->db = ((stmts_vtab*)p)->db;
+ *ppCursor = &pCur->base;
+ return SQLITE_OK;
+}
+
+/*
+** Destructor for a stmts_cursor.
+*/
+static int stmtsClose(sqlite3_vtab_cursor *cur){
+ sqlite3_free(cur);
+ return SQLITE_OK;
+}
+
+
+/*
+** Advance a stmts_cursor to its next row of output.
+*/
+static int stmtsNext(sqlite3_vtab_cursor *cur){
+ stmts_cursor *pCur = (stmts_cursor*)cur;
+ pCur->iRowid++;
+ pCur->pStmt = sqlite3_next_stmt(pCur->db, pCur->pStmt);
+ return SQLITE_OK;
+}
+
+/*
+** Return values of columns for the row at which the stmts_cursor
+** is currently pointing.
+*/
+static int stmtsColumn(
+ sqlite3_vtab_cursor *cur, /* The cursor */
+ sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
+ int i /* Which column to return */
+){
+ stmts_cursor *pCur = (stmts_cursor*)cur;
+ switch( i ){
+ case STMTS_COLUMN_PTR: {
+ sqlite3_result_int64(ctx, SQLITE_PTR_TO_INT64(pCur->pStmt));
+ break;
+ }
+ case STMTS_COLUMN_SQL: {
+ sqlite3_result_text(ctx, sqlite3_sql(pCur->pStmt), -1, SQLITE_TRANSIENT);
+ break;
+ }
+ case STMTS_COLUMN_NCOL: {
+ sqlite3_result_int(ctx, sqlite3_column_count(pCur->pStmt));
+ break;
+ }
+ case STMTS_COLUMN_RO: {
+ sqlite3_result_int(ctx, sqlite3_stmt_readonly(pCur->pStmt));
+ break;
+ }
+ case STMTS_COLUMN_BUSY: {
+ sqlite3_result_int(ctx, sqlite3_stmt_busy(pCur->pStmt));
+ break;
+ }
+ case STMTS_COLUMN_NSCAN:
+ case STMTS_COLUMN_NSORT:
+ case STMTS_COLUMN_NAIDX:
+ case STMTS_COLUMN_NSTEP: {
+ sqlite3_result_int(ctx, sqlite3_stmt_status(pCur->pStmt,
+ i-STMTS_COLUMN_NSCAN+SQLITE_STMTSTATUS_FULLSCAN_STEP, 0));
+ break;
+ }
+ }
+ return SQLITE_OK;
+}
+
+/*
+** Return the rowid for the current row. In this implementation, the
+** rowid is the same as the output value.
+*/
+static int stmtsRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+ stmts_cursor *pCur = (stmts_cursor*)cur;
+ *pRowid = pCur->iRowid;
+ return SQLITE_OK;
+}
+
+/*
+** Return TRUE if the cursor has been moved off of the last
+** row of output.
+*/
+static int stmtsEof(sqlite3_vtab_cursor *cur){
+ stmts_cursor *pCur = (stmts_cursor*)cur;
+ return pCur->pStmt==0;
+}
+
+/*
+** This method is called to "rewind" the stmts_cursor object back
+** to the first row of output. This method is always called at least
+** once prior to any call to stmtsColumn() or stmtsRowid() or
+** stmtsEof().
+*/
+static int stmtsFilter(
+ sqlite3_vtab_cursor *pVtabCursor,
+ int idxNum, const char *idxStr,
+ int argc, sqlite3_value **argv
+){
+ stmts_cursor *pCur = (stmts_cursor *)pVtabCursor;
+ pCur->pStmt = 0;
+ pCur->iRowid = 0;
+ return stmtsNext(pVtabCursor);
+}
+
+/*
+** SQLite will invoke this method one or more times while planning a query
+** that uses the generate_stmts virtual table. This routine needs to create
+** a query plan for each invocation and compute an estimated cost for that
+** plan.
+*/
+static int stmtsBestIndex(
+ 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
+** generate_stmts virtual table.
+*/
+static sqlite3_module stmtsModule = {
+ 0, /* iVersion */
+ 0, /* xCreate */
+ stmtsConnect, /* xConnect */
+ stmtsBestIndex, /* xBestIndex */
+ stmtsDisconnect, /* xDisconnect */
+ 0, /* xDestroy */
+ stmtsOpen, /* xOpen - open a cursor */
+ stmtsClose, /* xClose - close a cursor */
+ stmtsFilter, /* xFilter - configure scan constraints */
+ stmtsNext, /* xNext - advance a cursor */
+ stmtsEof, /* xEof - check for end of scan */
+ stmtsColumn, /* xColumn - read data */
+ stmtsRowid, /* xRowid - read data */
+ 0, /* xUpdate */
+ 0, /* xBegin */
+ 0, /* xSync */
+ 0, /* xCommit */
+ 0, /* xRollback */
+ 0, /* xFindMethod */
+ 0, /* xRename */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_stmts_init(
+ sqlite3 *db,
+ char **pzErrMsg,
+ const sqlite3_api_routines *pApi
+){
+ int rc = SQLITE_OK;
+ SQLITE_EXTENSION_INIT2(pApi);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ if( sqlite3_libversion_number()<3008012 ){
+ *pzErrMsg = sqlite3_mprintf(
+ "generate_stmts() requires SQLite 3.8.12 or later");
+ return SQLITE_ERROR;
+ }
+ rc = sqlite3_create_module(db, "stmts", &stmtsModule, 0);
+#endif
+ return rc;
+}
projects / thirdparty / sqlite.git / commitdiff
