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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Improved comments on one routine in the query planner. Improved diagnostic output for ".wheretrace". No production code changes.
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SHA3-256: 946b87a5282f00d8c532a51f4390e6de781b9a0d6626cb3c077c5622895dc540
User & Date: drh 2017-05-19 20:55:04
Context
2017-05-19
22:51
Prevent a possible NULL pointer dereference in the OP_Found opcode that can follow an OOM error. Problem found by OSS-Fuzz. check-in: c2de178f user: drh tags: trunk
20:55
Improved comments on one routine in the query planner. Improved diagnostic output for ".wheretrace". No production code changes. check-in: 946b87a5 user: drh tags: trunk
20:47
Fix a documentation typo. No changes to code. check-in: 68942a4f user: drh tags: trunk
Changes
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Changes to src/where.c.

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      pTemplate->nOut = p->nOut + 1;
    }
  }
}

/*
** Search the list of WhereLoops in *ppPrev looking for one that can be
** supplanted by pTemplate.
**
** Return NULL if the WhereLoop list contains an entry that can supplant
** pTemplate, in other words if pTemplate does not belong on the list.
**
** If pX is a WhereLoop that pTemplate can supplant, then return the
** link that points to pX.
**
** If pTemplate cannot supplant any existing element of the list but needs
** to be added to the list, then return a pointer to the tail of the list.

*/
static WhereLoop **whereLoopFindLesser(
  WhereLoop **ppPrev,
  const WhereLoop *pTemplate
){
  WhereLoop *p;
  for(p=(*ppPrev); p; ppPrev=&p->pNextLoop, p=*ppPrev){
................................................................................
  ** WhereLoop and insert it.
  */
#if WHERETRACE_ENABLED /* 0x8 */
  if( sqlite3WhereTrace & 0x8 ){
    if( p!=0 ){
      sqlite3DebugPrintf("replace: ");
      whereLoopPrint(p, pBuilder->pWC);
    }


    sqlite3DebugPrintf("    add: ");

    whereLoopPrint(pTemplate, pBuilder->pWC);
  }
#endif
  if( p==0 ){
    /* Allocate a new WhereLoop to add to the end of the list */
    *ppPrev = p = sqlite3DbMallocRawNN(db, sizeof(WhereLoop));
    if( p==0 ) return SQLITE_NOMEM_BKPT;







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      pTemplate->nOut = p->nOut + 1;
    }
  }
}

/*
** Search the list of WhereLoops in *ppPrev looking for one that can be
** replaced by pTemplate.
**
** Return NULL if pTemplate does not belong on the WhereLoop list.
** In other words if pTemplate ought to be dropped from further consideration.
**
** If pX is a WhereLoop that pTemplate can replace, then return the
** link that points to pX.
**
** If pTemplate cannot replace any existing element of the list but needs
** to be added to the list as a new entry, then return a pointer to the
** tail of the list.
*/
static WhereLoop **whereLoopFindLesser(
  WhereLoop **ppPrev,
  const WhereLoop *pTemplate
){
  WhereLoop *p;
  for(p=(*ppPrev); p; ppPrev=&p->pNextLoop, p=*ppPrev){
................................................................................
  ** WhereLoop and insert it.
  */
#if WHERETRACE_ENABLED /* 0x8 */
  if( sqlite3WhereTrace & 0x8 ){
    if( p!=0 ){
      sqlite3DebugPrintf("replace: ");
      whereLoopPrint(p, pBuilder->pWC);

      sqlite3DebugPrintf("   with: ");
    }else{
      sqlite3DebugPrintf("    add: ");
    }
    whereLoopPrint(pTemplate, pBuilder->pWC);
  }
#endif
  if( p==0 ){
    /* Allocate a new WhereLoop to add to the end of the list */
    *ppPrev = p = sqlite3DbMallocRawNN(db, sizeof(WhereLoop));
    if( p==0 ) return SQLITE_NOMEM_BKPT;