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Overview
Comment:Another minor optimization to OP_Transaction.
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SHA3-256: d80077aee3904e5d93164b342cae14d813de8e84e567462412751e06c7487d41
User & Date: drh 2018-06-06 17:45:51
Context
2018-06-06
18:50
Fix the sqlite3BeginTrans() calls within the snapshot extension. check-in: 1fef7ad2 user: drh tags: trunk
17:45
Another minor optimization to OP_Transaction. check-in: d80077ae user: drh tags: trunk
16:28
Change sqlite3BtreeBeginTrans() to return the BTREE_SCHEMA_COOKIE, for a small speed improvement when starting new transactions. check-in: a10662aa user: drh tags: trunk
Changes
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Changes to src/vdbe.c.

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** generation counter, then an SQLITE_SCHEMA error is raised and execution
** halts.  The sqlite3_step() wrapper function might then reprepare the
** statement and rerun it from the beginning.
*/
case OP_Transaction: {
  Btree *pBt;
  int iMeta = 0;
  int iGen = 0;

  assert( p->bIsReader );
  assert( p->readOnly==0 || pOp->p2==0 );
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( DbMaskTest(p->btreeMask, pOp->p1) );
  if( pOp->p2 && (db->flags & SQLITE_QueryOnly)!=0 ){
    rc = SQLITE_READONLY;
................................................................................

      /* Store the current value of the database handles deferred constraint
      ** counter. If the statement transaction needs to be rolled back,
      ** the value of this counter needs to be restored too.  */
      p->nStmtDefCons = db->nDeferredCons;
      p->nStmtDefImmCons = db->nDeferredImmCons;
    }

    /* Gather the schema version number for checking:





    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
    ** version is checked to ensure that the schema has not changed since the
    ** SQL statement was prepared.
    */
    iGen = db->aDb[pOp->p1].pSchema->iGeneration;
  }
  assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
  if( pOp->p5 && (iMeta!=pOp->p3 || iGen!=pOp->p4.i) ){
    sqlite3DbFree(db, p->zErrMsg);
    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    /* If the schema-cookie from the database file matches the cookie 
    ** stored with the in-memory representation of the schema, do
    ** not reload the schema from the database file.
    **
    ** If virtual-tables are in use, this is not just an optimization.







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** generation counter, then an SQLITE_SCHEMA error is raised and execution
** halts.  The sqlite3_step() wrapper function might then reprepare the
** statement and rerun it from the beginning.
*/
case OP_Transaction: {
  Btree *pBt;
  int iMeta = 0;


  assert( p->bIsReader );
  assert( p->readOnly==0 || pOp->p2==0 );
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( DbMaskTest(p->btreeMask, pOp->p1) );
  if( pOp->p2 && (db->flags & SQLITE_QueryOnly)!=0 ){
    rc = SQLITE_READONLY;
................................................................................

      /* Store the current value of the database handles deferred constraint
      ** counter. If the statement transaction needs to be rolled back,
      ** the value of this counter needs to be restored too.  */
      p->nStmtDefCons = db->nDeferredCons;
      p->nStmtDefImmCons = db->nDeferredImmCons;
    }
  }
  assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
  if( pOp->p5
   && (iMeta!=pOp->p3
      || db->aDb[pOp->p1].pSchema->iGeneration!=pOp->p4.i)
  ){
    /*
    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
    ** version is checked to ensure that the schema has not changed since the
    ** SQL statement was prepared.
    */




    sqlite3DbFree(db, p->zErrMsg);
    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    /* If the schema-cookie from the database file matches the cookie 
    ** stored with the in-memory representation of the schema, do
    ** not reload the schema from the database file.
    **
    ** If virtual-tables are in use, this is not just an optimization.