SQLite

/*
** 2006 June 10
**
** 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 contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.89 2009/05/20 20:10:47 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

/*
** The actual function that does the work of creating a new module.
** This function implements the sqlite3_create_module() and

*/
void sqlite3VtabUnlock(sqlite3 *db, sqlite3_vtab *pVtab){
  assert( pVtab->nRef>0 );
  pVtab->nRef--;
  assert(db);
  assert( sqlite3SafetyCheckOk(db) );
  if( pVtab->nRef==0 ){
#ifdef SQLITE_DEBUG
    if( db->magic==SQLITE_MAGIC_BUSY ){
      (void)sqlite3SafetyOff(db);
      pVtab->pModule->xDisconnect(pVtab);
      (void)sqlite3SafetyOn(db);
    } else 
#endif
    {
      pVtab->pModule->xDisconnect(pVtab);
    }
  }
}

/*
** Clear any and all virtual-table information from the Table record.

  if( pParse->db->flags & SQLITE_SharedCache ){
    sqlite3ErrorMsg(pParse, "Cannot use virtual tables in shared-cache mode");
    return;
  }

  sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, 0);
  pTable = pParse->pNewTable;
  if( pTable==0 ) return;
  assert( 0==pTable->pIndex );

  db = pParse->db;
  iDb = sqlite3SchemaToIndex(db, pTable->pSchema);
  assert( iDb>=0 );

  pTable->tabFlags |= TF_Virtual;

/*
** This routine takes the module argument that has been accumulating
** in pParse->zArg[] and appends it to the list of arguments on the
** virtual table currently under construction in pParse->pTable.
*/
static void addArgumentToVtab(Parse *pParse){
  if( pParse->sArg.z && ALWAYS(pParse->pNewTable) ){
    const char *z = (const char*)pParse->sArg.z;
    int n = pParse->sArg.n;
    sqlite3 *db = pParse->db;
    addModuleArgument(db, pParse->pNewTable, sqlite3DbStrNDup(db, z, n));
  }
}

  db->pVTab = pTab;
  rc = sqlite3SafetyOff(db);
  assert( rc==SQLITE_OK );
  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVtab, &zErr);
  rc2 = sqlite3SafetyOn(db);
  if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
  /* Justification of ALWAYS():  A correct vtab constructor must allocate
  ** the sqlite3_vtab object if successful. */
  if( rc==SQLITE_OK && ALWAYS(pVtab) ){
    pVtab->pModule = pMod->pModule;
    pVtab->nRef = 1;
    pTab->pVtab = pVtab;
  }

  if( SQLITE_OK!=rc ){
    if( zErr==0 ){

**
** This call is a no-op if table pTab is not a virtual table.
*/
int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
  Module *pMod;
  int rc = SQLITE_OK;

  assert( pTab );
  if( (pTab->tabFlags & TF_Virtual)==0 || pTab->pVtab ){
    return SQLITE_OK;
  }

  pMod = pTab->pMod;
  if( !pMod ){
    const char *zModule = pTab->azModuleArg[0];
    sqlite3ErrorMsg(pParse, "no such module: %s", zModule);

  if( !pMod ){
    *pzErr = sqlite3MPrintf(db, "no such module: %s", zModule);
    rc = SQLITE_ERROR;
  }else{
    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
  }

  /* Justification of ALWAYS():  The xConstructor method is required to
  ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
  if( rc==SQLITE_OK && ALWAYS(pTab->pVtab) ){
      rc = addToVTrans(db, pTab->pVtab);
  }

  return rc;
}

/*

/*
** This function is invoked by the vdbe to call the xDestroy method
** of the virtual table named zTab in database iDb. This occurs
** when a DROP TABLE is mentioned.
**
** This call is a no-op if zTab is not a virtual table.
*/
int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){

  int rc = SQLITE_OK;
  Table *pTab;

  pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);

  if( ALWAYS(pTab!=0 && pTab->pVtab!=0) ){
    int (*xDestroy)(sqlite3_vtab *pVTab) = pTab->pMod->pModule->xDestroy;
    rc = sqlite3SafetyOff(db);
    assert( rc==SQLITE_OK );

      rc = xDestroy(pTab->pVtab);

    (void)sqlite3SafetyOn(db);
    if( rc==SQLITE_OK ){
      int i;
      for(i=0; i<db->nVTrans; i++){
        if( db->aVTrans[i]==pTab->pVtab ){
          db->aVTrans[i] = db->aVTrans[--db->nVTrans];
          break;

** the offset of the method to call in the sqlite3_module structure.
**
** The array is cleared after invoking the callbacks. 
*/
static void callFinaliser(sqlite3 *db, int offset){
  int i;
  if( db->aVTrans ){
    for(i=0; i<db->nVTrans; i++){
      sqlite3_vtab *pVtab = db->aVTrans[i];
      int (*x)(sqlite3_vtab *);

      assert( pVtab!=0 );
      x = *(int (**)(sqlite3_vtab *))((char *)pVtab->pModule + offset);
      if( x ) x(pVtab);
      sqlite3VtabUnlock(db, pVtab);
    }
    sqlite3DbFree(db, db->aVTrans);
    db->nVTrans = 0;
    db->aVTrans = 0;

  int i;
  int rc = SQLITE_OK;
  int rcsafety;
  sqlite3_vtab **aVTrans = db->aVTrans;

  rc = sqlite3SafetyOff(db);
  db->aVTrans = 0;
  for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
    sqlite3_vtab *pVtab = aVTrans[i];
    int (*x)(sqlite3_vtab *);
    assert( pVtab!=0 );
    x = pVtab->pModule->xSync;
    if( x ){
      rc = x(pVtab);
      sqlite3DbFree(db, *pzErrmsg);
      *pzErrmsg = pVtab->zErrMsg;
      pVtab->zErrMsg = 0;
    }

int sqlite3VtabBegin(sqlite3 *db, sqlite3_vtab *pVtab){
  int rc = SQLITE_OK;
  const sqlite3_module *pModule;

  /* Special case: If db->aVTrans is NULL and db->nVTrans is greater
  ** than zero, then this function is being called from within a
  ** virtual module xSync() callback. It is illegal to write to 
  ** virtual module tables in this case, so return SQLITE_LOCKED.
  */
  if( sqlite3VtabInSync(db) ){
    return SQLITE_LOCKED;
  }
  if( !pVtab ){
    return SQLITE_OK;
  } 
  pModule = pVtab->pModule;

  if( pModule->xBegin ){
    int i;


    /* If pVtab is already in the aVTrans array, return early */
    for(i=0; i<db->nVTrans; i++){
      if( db->aVTrans[i]==pVtab ){
        return SQLITE_OK;
      }
    }

    /* Invoke the xBegin method */
    rc = pModule->xBegin(pVtab);

  FuncDef *pNew;
  int rc = 0;
  char *zLowerName;
  unsigned char *z;


  /* Check to see the left operand is a column in a virtual table */
  if( NEVER(pExpr==0) ) return pDef;
  if( pExpr->op!=TK_COLUMN ) return pDef;
  pTab = pExpr->pTab;
  if( NEVER(pTab==0) ) return pDef;
  if( (pTab->tabFlags & TF_Virtual)==0 ) return pDef;
  pVtab = pTab->pVtab;
  assert( pVtab!=0 );
  assert( pVtab->pModule!=0 );
  pMod = (sqlite3_module *)pVtab->pModule;
  if( pMod->xFindFunction==0 ) return pDef;
 

** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
** array so that an OP_VBegin will get generated for it.  Add pTab to the
** array if it is missing.  If pTab is already in the array, this routine
** is a no-op.
*/
void sqlite3VtabMakeWritable(Parse *pParse, Table *pTab){
  int i, n;
  Table **apVtabLock;

  assert( IsVirtual(pTab) );
  for(i=0; i<pParse->nVtabLock; i++){
    if( pTab==pParse->apVtabLock[i] ) return;
  }
  n = (pParse->nVtabLock+1)*sizeof(pParse->apVtabLock[0]);
  apVtabLock = sqlite3_realloc(pParse->apVtabLock, n);
  if( apVtabLock ){
    pParse->apVtabLock = apVtabLock;
    pParse->apVtabLock[pParse->nVtabLock++] = pTab;
  }else{
    pParse->db->mallocFailed = 1;
  }
}

#endif /* SQLITE_OMIT_VIRTUALTABLE */