Experimental changes to star-query planning heuristics.

FossilOrigin-Name: edabcc05595077340fa214f44979af28233124bdc72e1e18c1e90d6b22f2c5a8

manifest

@@ -1,5 +1,5 @@
-C Fix\sthe\sfileio\sextension\sfor\sWindows\sbuilds\sso\sthat\sit\sdoes\snot\sdepend\son\nthe\ssqlite3_win32_utf8_to_unicode()\sand\ssqlite3_win32_unicode_to_utf()\nroutines\sthat\sare\sfound\sin\sthe\sSQLite\score.\n[forum:/forumpost/2026-04-20T02:02:56Z|Forum\spost\s2026-04-20T02:02:56Z].
-D 2026-04-20T10:28:19.110
+C Experimental\schanges\sto\sstar-query\splanning\sheuristics.
+D 2026-04-21T11:01:00.293
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -817,7 +817,7 @@ F src/vxworks.h 9d18819c5235b49c2340a8a4d48195ec5d5afb637b152406de95a9436beeaeab
 F src/wal.c 7340d4f9bb827bd349127cac6b2cf0cb7f76b9fda645f7b9b0bf7a6e0b1e2e7c
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
-F src/where.c a00d35adeb2550249ba02f24e50eecfb99cba34c8d7d5299b295a591219a2e73
+F src/where.c d367b7ca282dab2de350cf4b1cc8ebb24832d53e566bf3f28467d262235a5d14
 F src/whereInt.h 8d94cb116c9e06205c3d5ac87af065fc044f8cf08bfdccd94b6ea1c1308e65da
 F src/wherecode.c 676cb6cb02878643e817d9917a2d3522b83a3736b2cedd3dc8a01d7bb92af6c2
 F src/whereexpr.c e9f7185fba366d9365aa7a97329609e4cf00b3dd0400d069fbaa5187350c17c6
@@ -2202,8 +2202,11 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh a554d13f6e5cf3760f041b87939e3d616ec6961859c3245e8ef701d1eafc2ca2
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P 13f0fd1daaf787bff6eded4a01c2cf47c79e52cf8812bb344995e28c015a4ed1
-R 31831ad7feed5c76e5222e938d48ee50
+P fe0414a9a3caf6af67f53a5f3534efd5d4bf4978ebce1c591ef62d6961e55701
+R 36dd0e170938bd6639bc2c50bc873597
+T *branch * star-query-experimental
+T *sym-star-query-experimental *
+T -sym-trunk *
 U drh
-Z c300dd262e9088f424ba1d42dfc17467
+Z 324a016049c1cead93b733ce49e0a615
 # Remove this line to create a well-formed Fossil manifest.

manifest.tags

@@ -1,2 +1,2 @@
-branch trunk
-tag trunk
+branch star-query-experimental
+tag star-query-experimental

manifest.uuid

@@ -1 +1 @@
-fe0414a9a3caf6af67f53a5f3534efd5d4bf4978ebce1c591ef62d6961e55701
+edabcc05595077340fa214f44979af28233124bdc72e1e18c1e90d6b22f2c5a8

src/where.c

@@ -5601,9 +5601,9 @@ static LogEst whereSortingCost(
 ** with a central "fact" table that is joined against multiple
 ** "dimension" tables, subject to the following constraints:
 **
-**   (aa)  Only a five-way or larger join is considered for this
+**   (aa)  Only a four-way or larger join is considered for this
 **         optimization.  If there are fewer than four terms in the FROM
-**         clause, this heuristic does not apply.
+**         clause, this heuristic does not apply. (Was 5 prior to 2026-02-10.)
 **
 **   (bb)  The join between the fact table and the dimension tables must
 **         be an INNER join.  CROSS and OUTER JOINs do not qualify.
@@ -5678,16 +5678,17 @@ static int computeMxChoice(WhereInfo *pWInfo){
     pWInfo->bStarDone = 1; /* Only do this computation once */
 
     /* Look for fact tables with three or more dimensions where the
-    ** dimension tables are not separately from the fact tables by an outer
+    ** dimension tables are not separated from the fact tables by an outer
     ** or cross join.  Adjust cost weights if found.
     */
     assert( !pWInfo->bStarUsed );
     aFromTabs = pWInfo->pTabList->a;
     pStart = pWInfo->pLoops;
     for(iFromIdx=0, m=1; iFromIdx<nLoop; iFromIdx++, m<<=1){
-      int nDep = 0;             /* Number of dimension tables */
+      int nDep = 0;             /* Number of joins against pFactTab */
       LogEst mxRun;             /* Maximum SCAN cost of a fact table */
-      Bitmask mSeen = 0;        /* Mask of dimension tables */
+      Bitmask mSeen = 0;        /* Mask of tabls joined to pFactTab */
+      Bitmask mDimen = 0;       /* Mask of dimension tables */
       SrcItem *pFactTab;        /* The candidate fact table */
 
       pFactTab = aFromTabs + iFromIdx;
@@ -5710,15 +5711,21 @@ static int computeMxChoice(WhereInfo *pWInfo){
          && (pWLoop->maskSelf & mSeen)==0  /* pWInfo not already a dependency */
          && (pWLoop->maskSelf & mSelfJoin)==0 /* Not a self-join */
         ){
-          if( aFromTabs[pWLoop->iTab].pSTab==pFactTab->pSTab ){
+          Table *pDim = aFromTabs[pWLoop->iTab].pSTab;
+          if( pDim==pFactTab->pSTab ){
             mSelfJoin |= m;
           }else{
             nDep++;
             mSeen |= pWLoop->maskSelf;
+            if( (pWLoop->wsFlags & WHERE_ONEROW)!=0
+             && pDim->nRowLogEst+33<=pFactTab->pSTab->nRowLogEst
+            ){
+              mDimen |= pWLoop->maskSelf;
+            }
           }
         }
       }
-      if( nDep<=2 ){
+      if( /*nDep<=2 ||*/ mDimen==0 ){
         continue; /* Constraint (cc) */
       }
 
@@ -5736,10 +5743,23 @@ static int computeMxChoice(WhereInfo *pWInfo){
 #endif
 #ifdef WHERETRACE_ENABLED /* 0x80000 */
       if( sqlite3WhereTrace & 0x80000 ){
+        const char *zSep = ", joins: ";
         Bitmask mShow = mSeen;
-        sqlite3DebugPrintf("Fact table %s(%d), dimensions:",
+        sqlite3DebugPrintf("Fact table %s(%d)",
             pFactTab->zAlias ? pFactTab->zAlias : pFactTab->pSTab->zName,
             iFromIdx);
+        for(pWLoop=pStart; pWLoop; pWLoop=pWLoop->pNextLoop){
+          if( mDimen & pWLoop->maskSelf ) continue;
+          if( mShow & pWLoop->maskSelf ){
+            SrcItem *pDim = aFromTabs + pWLoop->iTab;
+            mShow &= ~pWLoop->maskSelf;
+            sqlite3DebugPrintf("%s%s(%d)%s", zSep,
+              pDim->zAlias ? pDim->zAlias: pDim->pSTab->zName, pWLoop->iTab);
+            zSep = " ";
+          }
+        }
+        mShow = mDimen;
+        sqlite3DebugPrintf(", dimensions:");
         for(pWLoop=pStart; pWLoop; pWLoop=pWLoop->pNextLoop){
           if( mShow & pWLoop->maskSelf ){
             SrcItem *pDim = aFromTabs + pWLoop->iTab;
@@ -5766,7 +5786,7 @@ static int computeMxChoice(WhereInfo *pWInfo){
       /* Increase the cost of table scans for dimension tables to be
       ** slightly more than the maximum cost of the fact table */
       for(pWLoop=pStart; pWLoop; pWLoop=pWLoop->pNextLoop){
-        if( (pWLoop->maskSelf & mSeen)==0 ) continue;
+        if( (pWLoop->maskSelf & mDimen)==0 ) continue;
         if( pWLoop->nLTerm ) continue;
         if( pWLoop->rRun<mxRun ){
 #ifdef WHERETRACE_ENABLED /* 0x80000 */
@@ -5780,6 +5800,17 @@ static int computeMxChoice(WhereInfo *pWInfo){
           pWLoop->rStarDelta = mxRun - pWLoop->rRun;
 #endif /* WHERETRACE_ENABLED */
           pWLoop->rRun = mxRun;
+        }else{
+#ifdef WHERETRACE_ENABLED /* 0x80000 */
+          if( sqlite3WhereTrace & 0x80000 ){
+            SrcItem *pDim = aFromTabs + pWLoop->iTab;
+            sqlite3DebugPrintf(
+              "SCAN cost of %s is already %d, higher than %d\n",
+              pDim->zAlias ? pDim->zAlias: pDim->pSTab->zName,
+              pWLoop->rRun, mxRun
+            );
+          }
+#endif /* WHERETRACE_ENABLED */
         }
       }
     }