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Infrastructure for the bytecode() table-valued function. The function itself
is not yet implemented. FossilOrigin-Name: 2795f0d633577e0de66b389d9e8e44c55e85975bdc62f1a0b8f93959d19b22bf
This commit is contained in:
drh
223
src/vdbevtab.c
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223
src/vdbevtab.c
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/*
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** 2020-03-23
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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**
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** This file implements virtual-tables for examining the bytecode content
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** of a prepared statement.
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*/
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#ifdef SQLITE_ENABLE_BYTECODE_VTAB
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#include "sqliteInt.h"
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#include "vdbeInt.h"
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/* An instance of the bytecode() table-valued function.
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*/
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typedef struct bytecodevtab_vtab bytecodevtab_vtab;
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struct bytecodevtab_vtab {
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sqlite3_vtab base; /* Base class - must be first */
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sqlite3_stmt *pStmt; /* The statement whose bytecode is to be displayed */
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};
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/* A cursor for scanning through the bytecode
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*/
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typedef struct bytecodevtab_cursor bytecodevtab_cursor;
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struct bytecodevtab_cursor {
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sqlite3_vtab_cursor base; /* Base class - must be first */
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sqlite3_int64 iRowid; /* The rowid */
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};
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/*
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** Create a new bytecode() table-valued function.
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*/
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static int bytecodevtabConnect(
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sqlite3 *db,
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void *pAux,
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int argc, const char *const*argv,
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sqlite3_vtab **ppVtab,
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char **pzErr
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){
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bytecodevtab_vtab *pNew;
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int rc;
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rc = sqlite3_declare_vtab(db,
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"CREATE TABLE x("
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"addr INT,"
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"opcode TEXT,"
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"p1 INT,"
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"p2 INT,"
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"p3 INT,"
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"p4 TEXT,"
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"p5 INT,"
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"comment TEXT,"
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"subprog TEXT,"
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"stmt HIDDEN"
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");"
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);
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if( rc==SQLITE_OK ){
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pNew = sqlite3_malloc( sizeof(*pNew) );
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*ppVtab = (sqlite3_vtab*)pNew;
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if( pNew==0 ) return SQLITE_NOMEM;
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memset(pNew, 0, sizeof(*pNew));
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}
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return rc;
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}
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/*
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** This method is the destructor for bytecodevtab_vtab objects.
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*/
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static int bytecodevtabDisconnect(sqlite3_vtab *pVtab){
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bytecodevtab_vtab *p = (bytecodevtab_vtab*)pVtab;
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sqlite3_free(p);
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return SQLITE_OK;
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}
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/*
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** Constructor for a new bytecodevtab_cursor object.
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*/
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static int bytecodevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
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bytecodevtab_cursor *pCur;
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pCur = sqlite3_malloc( sizeof(*pCur) );
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if( pCur==0 ) return SQLITE_NOMEM;
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memset(pCur, 0, sizeof(*pCur));
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*ppCursor = &pCur->base;
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return SQLITE_OK;
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}
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/*
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** Destructor for a bytecodevtab_cursor.
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*/
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static int bytecodevtabClose(sqlite3_vtab_cursor *cur){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
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sqlite3_free(pCur);
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return SQLITE_OK;
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}
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/*
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** Advance a bytecodevtab_cursor to its next row of output.
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*/
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static int bytecodevtabNext(sqlite3_vtab_cursor *cur){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
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pCur->iRowid++;
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return SQLITE_OK;
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}
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/*
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** Return values of columns for the row at which the bytecodevtab_cursor
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** is currently pointing.
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*/
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static int bytecodevtabColumn(
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sqlite3_vtab_cursor *cur, /* The cursor */
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sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
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int i /* Which column to return */
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){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
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#if 0
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switch( i ){
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case TEMPLATEVTAB_A:
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sqlite3_result_int(ctx, 1000 + pCur->iRowid);
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break;
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default:
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assert( i==TEMPLATEVTAB_B );
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sqlite3_result_int(ctx, 2000 + pCur->iRowid);
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break;
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}
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#endif
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return SQLITE_OK;
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}
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/*
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** Return the rowid for the current row. In this implementation, the
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** rowid is the same as the output value.
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*/
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static int bytecodevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
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*pRowid = pCur->iRowid;
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return SQLITE_OK;
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}
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/*
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** Return TRUE if the cursor has been moved off of the last
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** row of output.
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*/
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static int bytecodevtabEof(sqlite3_vtab_cursor *cur){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
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return pCur->iRowid>=10;
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}
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/*
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** This method is called to "rewind" the bytecodevtab_cursor object back
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** to the first row of output. This method is always called at least
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** once prior to any call to bytecodevtabColumn() or bytecodevtabRowid() or
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** bytecodevtabEof().
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*/
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static int bytecodevtabFilter(
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sqlite3_vtab_cursor *pVtabCursor,
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int idxNum, const char *idxStr,
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int argc, sqlite3_value **argv
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){
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bytecodevtab_cursor *pCur = (bytecodevtab_cursor *)pVtabCursor;
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pCur->iRowid = 1;
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return SQLITE_OK;
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}
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/*
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** SQLite will invoke this method one or more times while planning a query
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** that uses the virtual table. This routine needs to create
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** a query plan for each invocation and compute an estimated cost for that
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** plan.
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*/
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static int bytecodevtabBestIndex(
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sqlite3_vtab *tab,
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sqlite3_index_info *pIdxInfo
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){
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pIdxInfo->estimatedCost = (double)10;
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pIdxInfo->estimatedRows = 10;
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return SQLITE_OK;
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}
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/*
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** This following structure defines all the methods for the
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** virtual table.
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*/
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static sqlite3_module bytecodevtabModule = {
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/* iVersion */ 0,
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/* xCreate */ 0,
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/* xConnect */ bytecodevtabConnect,
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/* xBestIndex */ bytecodevtabBestIndex,
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/* xDisconnect */ bytecodevtabDisconnect,
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/* xDestroy */ 0,
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/* xOpen */ bytecodevtabOpen,
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/* xClose */ bytecodevtabClose,
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/* xFilter */ bytecodevtabFilter,
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/* xNext */ bytecodevtabNext,
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/* xEof */ bytecodevtabEof,
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/* xColumn */ bytecodevtabColumn,
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/* xRowid */ bytecodevtabRowid,
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/* xUpdate */ 0,
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/* xBegin */ 0,
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/* xSync */ 0,
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/* xCommit */ 0,
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/* xRollback */ 0,
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/* xFindMethod */ 0,
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/* xRename */ 0,
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/* xSavepoint */ 0,
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/* xRelease */ 0,
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/* xRollbackTo */ 0,
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/* xShadowName */ 0
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};
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int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){
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int rc;
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rc = sqlite3_create_module(db, "bytecodevtab", &bytecodevtabModule, 0);
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return rc;
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}
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#endif /* SQLITE_ENABLE_BYTECODE_VTAB */
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