Merge recent trunk changes into sessions.

FossilOrigin-Name: 95e77efe076ab421bd246119c47dba5dacf9d087

1 files changed, 159 insertions, 74 deletions

diff --git a/src/where.c b/src/where.c
index dd6893f69..e51eee535 100644
--- a/src/where.c
+++ b/src/where.c
@@ -2841,7 +2841,7 @@ static Bitmask codeOneLoopStart(
     pLevel->p1 = iCur;
     pLevel->p2 = sqlite3VdbeCurrentAddr(v);
     sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
-    sqlite3ExprCachePop(pParse, 1);
+    sqlite3ExprCachePop(pParse);
   }else
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 
@@ -3712,6 +3712,124 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
 }
 
 /*
+** Return TRUE if the set of WHERE clause terms used by pA is a proper
+** subset of the WHERE clause terms used by pB.
+*/
+static int whereLoopProperSubset(const WhereLoop *pA, const WhereLoop *pB){
+  int i, j;
+  assert( pA->nLTerm<pB->nLTerm );  /* Checked by calling function */
+  for(j=0, i=pA->nLTerm-1; i>=0 && j>=0; i--){
+    for(j=pB->nLTerm-1; j>=0; j--){
+      if( pB->aLTerm[j]==pA->aLTerm[i] ) break;
+    }
+  }
+  return j>=0;
+}
+
+/*
+** Try to adjust the cost of WhereLoop pTemplate upwards or downwards so
+** that:
+**
+**   (1) pTemplate costs less than any other WhereLoops that are a proper
+**       subset of pTemplate
+**
+**   (2) pTemplate costs more than any other WhereLoops for which pTemplate
+**       is a proper subset.
+**
+** To say "WhereLoop X is a proper subset of Y" means that X uses fewer
+** WHERE clause terms than Y and that every WHERE clause term used by X is
+** also used by Y.
+*/
+static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
+  if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
+  for(; p; p=p->pNextLoop){
+    if( p->iTab!=pTemplate->iTab ) continue;
+    if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
+    if( p->nLTerm<pTemplate->nLTerm
+     && (p->rRun<pTemplate->rRun || (p->rRun==pTemplate->rRun &&
+                                     p->nOut<=pTemplate->nOut))
+     && whereLoopProperSubset(p, pTemplate)
+    ){
+      pTemplate->rRun = p->rRun;
+      pTemplate->nOut = p->nOut - 1;
+    }else
+    if( p->nLTerm>pTemplate->nLTerm
+     && (p->rRun>pTemplate->rRun || (p->rRun==pTemplate->rRun &&
+                                     p->nOut>=pTemplate->nOut))
+     && whereLoopProperSubset(pTemplate, p)
+    ){
+      pTemplate->rRun = p->rRun;
+      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){
+    if( p->iTab!=pTemplate->iTab || p->iSortIdx!=pTemplate->iSortIdx ){
+      /* If either the iTab or iSortIdx values for two WhereLoop are different
+      ** then those WhereLoops need to be considered separately.  Neither is
+      ** a candidate to replace the other. */
+      continue;
+    }
+    /* In the current implementation, the rSetup value is either zero
+    ** or the cost of building an automatic index (NlogN) and the NlogN
+    ** is the same for compatible WhereLoops. */
+    assert( p->rSetup==0 || pTemplate->rSetup==0 
+                 || p->rSetup==pTemplate->rSetup );
+
+    /* whereLoopAddBtree() always generates and inserts the automatic index
+    ** case first.  Hence compatible candidate WhereLoops never have a larger
+    ** rSetup. Call this SETUP-INVARIANT */
+    assert( p->rSetup>=pTemplate->rSetup );
+
+    /* If existing WhereLoop p is better than pTemplate, pTemplate can be
+    ** discarded.  WhereLoop p is better if:
+    **   (1)  p has no more dependencies than pTemplate, and
+    **   (2)  p has an equal or lower cost than pTemplate
+    */
+    if( (p->prereq & pTemplate->prereq)==p->prereq    /* (1)  */
+     && p->rSetup<=pTemplate->rSetup                  /* (2a) */
+     && p->rRun<=pTemplate->rRun                      /* (2b) */
+     && p->nOut<=pTemplate->nOut                      /* (2c) */
+    ){
+      return 0;  /* Discard pTemplate */
+    }
+
+    /* If pTemplate is always better than p, then cause p to be overwritten
+    ** with pTemplate.  pTemplate is better than p if:
+    **   (1)  pTemplate has no more dependences than p, and
+    **   (2)  pTemplate has an equal or lower cost than p.
+    */
+    if( (p->prereq & pTemplate->prereq)==pTemplate->prereq   /* (1)  */
+     && p->rRun>=pTemplate->rRun                             /* (2a) */
+     && p->nOut>=pTemplate->nOut                             /* (2b) */
+    ){
+      assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */
+      break;   /* Cause p to be overwritten by pTemplate */
+    }
+  }
+  return ppPrev;
+}
+
+/*
 ** Insert or replace a WhereLoop entry using the template supplied.
 **
 ** An existing WhereLoop entry might be overwritten if the new template
@@ -3720,25 +3838,23 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
 ** fewer dependencies than the template.  Otherwise a new WhereLoop is
 ** added based on the template.
 **
-** If pBuilder->pOrSet is not NULL then we only care about only the
+** If pBuilder->pOrSet is not NULL then we care about only the
 ** prerequisites and rRun and nOut costs of the N best loops.  That
 ** information is gathered in the pBuilder->pOrSet object.  This special
 ** processing mode is used only for OR clause processing.
 **
 ** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
 ** still might overwrite similar loops with the new template if the
-** template is better.  Loops may be overwritten if the following 
+** new template is better.  Loops may be overwritten if the following 
 ** conditions are met:
 **
 **    (1)  They have the same iTab.
 **    (2)  They have the same iSortIdx.
 **    (3)  The template has same or fewer dependencies than the current loop
 **    (4)  The template has the same or lower cost than the current loop
-**    (5)  The template uses more terms of the same index but has no additional
-**         dependencies          
 */
 static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
-  WhereLoop **ppPrev, *p, *pNext = 0;
+  WhereLoop **ppPrev, *p;
   WhereInfo *pWInfo = pBuilder->pWInfo;
   sqlite3 *db = pWInfo->pParse->db;
 
@@ -3761,64 +3877,23 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
     return SQLITE_OK;
   }
 
-  /* Search for an existing WhereLoop to overwrite, or which takes
-  ** priority over pTemplate.
+  /* Look for an existing WhereLoop to replace with pTemplate
   */
-  for(ppPrev=&pWInfo->pLoops, p=*ppPrev; p; ppPrev=&p->pNextLoop, p=*ppPrev){
-    if( p->iTab!=pTemplate->iTab || p->iSortIdx!=pTemplate->iSortIdx ){
-      /* If either the iTab or iSortIdx values for two WhereLoop are different
-      ** then those WhereLoops need to be considered separately.  Neither is
-      ** a candidate to replace the other. */
-      continue;
-    }
-    /* In the current implementation, the rSetup value is either zero
-    ** or the cost of building an automatic index (NlogN) and the NlogN
-    ** is the same for compatible WhereLoops. */
-    assert( p->rSetup==0 || pTemplate->rSetup==0 
-                 || p->rSetup==pTemplate->rSetup );
-
-    /* whereLoopAddBtree() always generates and inserts the automatic index
-    ** case first.  Hence compatible candidate WhereLoops never have a larger
-    ** rSetup. Call this SETUP-INVARIANT */
-    assert( p->rSetup>=pTemplate->rSetup );
+  whereLoopAdjustCost(pWInfo->pLoops, pTemplate);
+  ppPrev = whereLoopFindLesser(&pWInfo->pLoops, pTemplate);
 
-    if( (p->prereq & pTemplate->prereq)==p->prereq
-     && p->rSetup<=pTemplate->rSetup
-     && p->rRun<=pTemplate->rRun
-     && p->nOut<=pTemplate->nOut
-    ){
-      /* This branch taken when p is equal or better than pTemplate in 
-      ** all of (1) dependencies (2) setup-cost, (3) run-cost, and
-      ** (4) number of output rows. */
-      assert( p->rSetup==pTemplate->rSetup );
-      if( p->prereq==pTemplate->prereq
-       && p->nLTerm<pTemplate->nLTerm
-       && (p->wsFlags & pTemplate->wsFlags & WHERE_INDEXED)!=0
-       && (p->u.btree.pIndex==pTemplate->u.btree.pIndex
-          || pTemplate->rRun+p->nLTerm<=p->rRun+pTemplate->nLTerm)
-      ){
-        /* Overwrite an existing WhereLoop with an similar one that uses
-        ** more terms of the index */
-        pNext = p->pNextLoop;
-        break;
-      }else{
-        /* pTemplate is not helpful.
-        ** Return without changing or adding anything */
-        goto whereLoopInsert_noop;
-      }
-    }
-    if( (p->prereq & pTemplate->prereq)==pTemplate->prereq
-     && p->rRun>=pTemplate->rRun
-     && p->nOut>=pTemplate->nOut
-    ){
-      /* Overwrite an existing WhereLoop with a better one: one that is
-      ** better at one of (1) dependencies, (2) setup-cost, (3) run-cost
-      ** or (4) number of output rows, and is no worse in any of those
-      ** categories. */
-      assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */
-      pNext = p->pNextLoop;
-      break;
+  if( ppPrev==0 ){
+    /* There already exists a WhereLoop on the list that is better
+    ** than pTemplate, so just ignore pTemplate */
+#if WHERETRACE_ENABLED /* 0x8 */
+    if( sqlite3WhereTrace & 0x8 ){
+      sqlite3DebugPrintf("ins-noop: ");
+      whereLoopPrint(pTemplate, pBuilder->pWC);
     }
+#endif
+    return SQLITE_OK;  
+  }else{
+    p = *ppPrev;
   }
 
   /* If we reach this point it means that either p[] should be overwritten
@@ -3836,13 +3911,33 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
   }
 #endif
   if( p==0 ){
-    p = sqlite3DbMallocRaw(db, sizeof(WhereLoop));
+    /* Allocate a new WhereLoop to add to the end of the list */
+    *ppPrev = p = sqlite3DbMallocRaw(db, sizeof(WhereLoop));
     if( p==0 ) return SQLITE_NOMEM;
     whereLoopInit(p);
+    p->pNextLoop = 0;
+  }else{
+    /* We will be overwriting WhereLoop p[].  But before we do, first
+    ** go through the rest of the list and delete any other entries besides
+    ** p[] that are also supplated by pTemplate */
+    WhereLoop **ppTail = &p->pNextLoop;
+    WhereLoop *pToDel;
+    while( *ppTail ){
+      ppTail = whereLoopFindLesser(ppTail, pTemplate);
+      if( NEVER(ppTail==0) ) break;
+      pToDel = *ppTail;
+      if( pToDel==0 ) break;
+      *ppTail = pToDel->pNextLoop;
+#if WHERETRACE_ENABLED /* 0x8 */
+      if( sqlite3WhereTrace & 0x8 ){
+        sqlite3DebugPrintf("ins-del: ");
+        whereLoopPrint(pToDel, pBuilder->pWC);
+      }
+#endif
+      whereLoopDelete(db, pToDel);
+    }
   }
   whereLoopXfer(db, p, pTemplate);
-  p->pNextLoop = pNext;
-  *ppPrev = p;
   if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
     Index *pIndex = p->u.btree.pIndex;
     if( pIndex && pIndex->tnum==0 ){
@@ -3850,16 +3945,6 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
     }
   }
   return SQLITE_OK;
-
-  /* Jump here if the insert is a no-op */
-whereLoopInsert_noop:
-#if WHERETRACE_ENABLED /* 0x8 */
-  if( sqlite3WhereTrace & 0x8 ){
-    sqlite3DebugPrintf("ins-noop: ");
-    whereLoopPrint(pTemplate, pBuilder->pWC);
-  }
-#endif
-  return SQLITE_OK;  
 }
 
 /*