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Comment:Use compile-time options SQLITE_QUERY_PLANNER_LIMIT and SQLITE_QUERY_PLANNER_LIMIT_INCR to control the value for WhereLoopBuilder.iPlanLimit, rather than embedding magic numbers in the code.
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SHA3-256:903e501894b2a5dd7055b5154d74d4a47a619f76e66485a4d62b6259f10723d6
User & Date: drh 2018-09-24 12:37:01
Context
2018-09-24
14:10
Allow a writable virtual table to have a schema with an INTEGER PRIMARY KEY and WITHOUT ROWID. This fixes ticket [f25d5ceebe1d710ff61a571e395356869d8272ef]. Test case in TH3. check-in: 5a38d928 user: drh tags: trunk
12:37
Use compile-time options SQLITE_QUERY_PLANNER_LIMIT and SQLITE_QUERY_PLANNER_LIMIT_INCR to control the value for WhereLoopBuilder.iPlanLimit, rather than embedding magic numbers in the code. check-in: 903e5018 user: drh tags: trunk
10:47
Increase the initial value of WhereLoopBuilder.iPlanLimit to 20K. Issue a warning if the iPlanLimit reaches zero. check-in: 3dd35f51 user: drh tags: trunk
Changes
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Changes to src/where.c.

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  int rc = SQLITE_OK;
  WhereLoop *pNew;
  u8 priorJointype = 0;

  /* Loop over the tables in the join, from left to right */
  pNew = pBuilder->pNew;
  whereLoopInit(pNew);
  /* Some pathological queries provide an unreasonable number of indexing
  ** options. The iPlanLimit value prevents these queries from taking up
  ** too much time in the planner. When iPlanLimit reaches zero, no further
  ** index+constraint options are considered. Seed iPlanLimit to 20K but
  ** also add an extra 1K to each table of the join, to ensure that each
  ** table at least gets 1K opportunities. */
  pBuilder->iPlanLimit = 20000;
  for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
    Bitmask mUnusable = 0;
    pNew->iTab = iTab;
    pBuilder->iPlanLimit += 1000;  /* 1000 bonus for each table in the join */
    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
    if( ((pItem->fg.jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
      /* This condition is true when pItem is the FROM clause term on the
      ** right-hand-side of a LEFT or CROSS JOIN.  */
      mPrereq = mPrior;
    }
    priorJointype = pItem->fg.jointype;







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  int rc = SQLITE_OK;
  WhereLoop *pNew;
  u8 priorJointype = 0;

  /* Loop over the tables in the join, from left to right */
  pNew = pBuilder->pNew;
  whereLoopInit(pNew);






  pBuilder->iPlanLimit = SQLITE_QUERY_PLANNER_LIMIT;
  for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
    Bitmask mUnusable = 0;
    pNew->iTab = iTab;
    pBuilder->iPlanLimit += SQLITE_QUERY_PLANNER_LIMIT_INCR;
    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
    if( ((pItem->fg.jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
      /* This condition is true when pItem is the FROM clause term on the
      ** right-hand-side of a LEFT or CROSS JOIN.  */
      mPrereq = mPrior;
    }
    priorJointype = pItem->fg.jointype;

Changes to src/whereInt.h.

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  unsigned int bldFlags;    /* SQLITE_BLDF_* flags */
  unsigned int iPlanLimit;  /* Search limiter */
};

/* Allowed values for WhereLoopBuider.bldFlags */
#define SQLITE_BLDF_INDEXED  0x0001   /* An index is used */
#define SQLITE_BLDF_UNIQUE   0x0002   /* All keys of a UNIQUE index used */





















/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.







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  unsigned int bldFlags;    /* SQLITE_BLDF_* flags */
  unsigned int iPlanLimit;  /* Search limiter */
};

/* Allowed values for WhereLoopBuider.bldFlags */
#define SQLITE_BLDF_INDEXED  0x0001   /* An index is used */
#define SQLITE_BLDF_UNIQUE   0x0002   /* All keys of a UNIQUE index used */

/* The WhereLoopBuilder.iPlanLimit is used to limit the number of
** index+constraint combinations the query planner will consider for a
** particular query.  If this parameter is unlimited, then certain
** pathological queries can spend excess time in the sqlite3WhereBegin()
** routine.  The limit is high enough that is should not impact real-world
** queries.
**
** SQLITE_QUERY_PLANNER_LIMIT is the baseline limit.  The limit is
** increased by SQLITE_QUERY_PLANNER_LIMIT_INCR before each term of the FROM
** clause is processed, so that every table in a join is guaranteed to be
** able to propose a some index+constraint combinations even if the initial
** baseline limit was exhausted by prior tables of the join.
*/
#ifndef SQLITE_QUERY_PLANNER_LIMIT
# define SQLITE_QUERY_PLANNER_LIMIT 20000
#endif
#ifndef SQLITE_QUERY_PLANNER_LIMIT_INCR
# define SQLITE_QUERY_PLANNER_LIMIT_INCR 1000
#endif

/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.