Minor tweaks to the star-query optimization in the query planner.

FossilOrigin-Name: 5021e114b251467fee6a39749c88ec581ee1f7d50093b02a44dc300db0c0a1c5

diff --git a/manifest b/manifest
index b4d9ba30cc7fde62bc4946f94a1f130d136bde58..c56b3182d15684302f38463b9cf03fef869bd31a 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Immediately\sreset\sall\spending\sprepared\sstatements\son\sany\scall\sto\nsqlite3_set_authorizer(),\seven\sif\sthe\sauthorizer\sis\sbeing\sdisabled.
-D 2026-02-09T19:58:04.336
+C Minor\stweaks\sto\sthe\sstar-query\soptimization\sin\sthe\squery\splanner.
+D 2026-02-10T18:28:41.694
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -820,7 +820,7 @@ F src/vxworks.h 9d18819c5235b49c2340a8a4d48195ec5d5afb637b152406de95a9436beeaeab
 F src/wal.c 505a98fbc599a971d92cb90371cf54546c404cd61e04fd093e7b0c8ff978f9b6
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
-F src/where.c f1237550a01ccbc70141a523661173ddf802f48f7fe94feab9151a66f80c0d9d
+F src/where.c 7a7fe745dd8104d0276a3d3f6e6ac7f087af3dd9f34a90bc937e5e7aea817e15
 F src/whereInt.h 8d94cb116c9e06205c3d5ac87af065fc044f8cf08bfdccd94b6ea1c1308e65da
 F src/wherecode.c 783ecd30061c875c919a5163e4b55f9a0eccdaf7c9b17ad2908a1668a8766bc4
 F src/whereexpr.c bb649ce81bd6dc0eabfa2533ff5656fc7a16411e520a6c59be43e73e51503cce
@@ -2194,8 +2194,8 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh d924598cf2f55a4ecbc2aeb055c10bd5f48114793e7ba25f9585435da29e7e98
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P 021e48e28931afd781e76db6293e60fd2ffb8377cb1051e8b802f2743a10fa5d
-R 8e691803f449515bcdce3d4bea85fe54
+P 5c0468acd1a12f7fd01b9974250fb42c5811939dc2319729a1ef93c073dc0071
+R a8a8cc651a9935d9d998addfdb1931ef
 U drh
-Z d57a142f836bbfe387f4f44113a90926
+Z 9ecd247afb8d5321506fc416f50001e3
 # Remove this line to create a well-formed Fossil manifest.

diff --git a/manifest.uuid b/manifest.uuid
index cb415b67fd86987205cca0eb49300dd3f91e47ca..bab5268fc0ef60d77f32294f062d066524440a82 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-5c0468acd1a12f7fd01b9974250fb42c5811939dc2319729a1ef93c073dc0071
+5021e114b251467fee6a39749c88ec581ee1f7d50093b02a44dc300db0c0a1c5

diff --git a/src/where.c b/src/where.c
index 6caa6bfb5298bf41a1a0b45a92796937787a949f..946d9fede5de6d78bd1e16bced039957acbf07d1 100644 (file)
--- a/src/where.c
+++ b/src/where.c
@@ -5588,12 +5588,21 @@ static LogEst whereSortingCost(
 **     12    otherwise
 **
 ** For the purposes of this heuristic, a star-query is defined as a query
-** with a large central table that is joined using an INNER JOIN,
-** not CROSS or OUTER JOINs, against four or more smaller tables.
-** The central table is called the "fact" table.  The smaller tables
-** that get joined are "dimension tables".  Also, any table that is
-** self-joined cannot be a dimension table; we assume that dimension
-** tables may only be joined against fact tables.
+** 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
+**         optimization.  If there are fewer than four terms in the FROM
+**         clause, this heuristic does not apply.
+**
+**   (bb)  The join between the fact table and the dimension tables must
+**         be an INNER join.  CROSS and OUTER JOINs do not qualify.
+**
+**   (cc)  A table must have 3 or more dimension tables in order to be
+**         considered a fact table. (Was 4 prior to 2026-02-10.)
+**
+**   (dd)  A table that is a self-join cannot be a dimension table.
+**         Dimension tables are joined against fact tables.
 **
 ** SIDE EFFECT:  (and really the whole point of this subroutine)
 **
@@ -5646,7 +5655,7 @@ static int computeMxChoice(WhereInfo *pWInfo){
   }
 #endif /* SQLITE_DEBUG */
 
-  if( nLoop>=5
+  if( nLoop>=4  /* Constraint (aa) */
    && !pWInfo->bStarDone
    && OptimizationEnabled(pWInfo->pParse->db, SQLITE_StarQuery)
   ){
@@ -5658,7 +5667,7 @@ static int computeMxChoice(WhereInfo *pWInfo){
 
     pWInfo->bStarDone = 1; /* Only do this computation once */
 
-    /* Look for fact tables with four or more dimensions where the
+    /* Look for fact tables with three or more dimensions where the
     ** dimension tables are not separately from the fact tables by an outer
     ** or cross join.  Adjust cost weights if found.
     */
@@ -5675,18 +5684,17 @@ static int computeMxChoice(WhereInfo *pWInfo){
       if( (pFactTab->fg.jointype & (JT_OUTER|JT_CROSS))!=0 ){
         /* If the candidate fact-table is the right table of an outer join
         ** restrict the search for dimension-tables to be tables to the right
-        ** of the fact-table. */
-        if( iFromIdx+4 > nLoop ) break;  /* Impossible to reach nDep>=4 */
+        ** of the fact-table.  Constraint (bb) */
+        if( iFromIdx+3 > nLoop ){
+          break;  /* ^-- Impossible to reach nDep>=2 - Constraint (cc) */
+        }
         while( pStart && pStart->iTab<=iFromIdx ){
           pStart = pStart->pNextLoop;
         }
       }
       for(pWLoop=pStart; pWLoop; pWLoop=pWLoop->pNextLoop){
         if( (aFromTabs[pWLoop->iTab].fg.jointype & (JT_OUTER|JT_CROSS))!=0 ){
-          /* Fact-tables and dimension-tables cannot be separated by an
-          ** outer join (at least for the definition of fact- and dimension-
-          ** used by this heuristic). */
-          break;
+          break; /* Constraint (bb) */
         }
         if( (pWLoop->prereq & m)!=0        /* pWInfo depends on iFromIdx */
          && (pWLoop->maskSelf & mSeen)==0  /* pWInfo not already a dependency */
@@ -5700,7 +5708,9 @@ static int computeMxChoice(WhereInfo *pWInfo){
           }
         }
       }
-      if( nDep<=3 ) continue;
+      if( nDep<=2 ){
+        continue; /* Constraint (cc) */
+      }
 
       /* If we reach this point, it means that pFactTab is a fact table
       ** with four or more dimensions connected by inner joins.  Proceed
@@ -5713,6 +5723,23 @@ static int computeMxChoice(WhereInfo *pWInfo){
           pWLoop->rStarDelta = 0;
         }
       }
+#endif
+#ifdef WHERETRACE_ENABLED /* 0x80000 */
+      if( sqlite3WhereTrace & 0x80000 ){
+        Bitmask mShow = mSeen;
+        sqlite3DebugPrintf("Fact table %s(%d), dimensions:",
+            pFactTab->zAlias ? pFactTab->zAlias : pFactTab->pSTab->zName,
+            iFromIdx);
+        for(pWLoop=pStart; pWLoop; pWLoop=pWLoop->pNextLoop){
+          if( mShow & pWLoop->maskSelf ){
+            SrcItem *pDim = aFromTabs + pWLoop->iTab;
+            mShow &= ~pWLoop->maskSelf;
+            sqlite3DebugPrintf(" %s(%d)",
+              pDim->zAlias ? pDim->zAlias: pDim->pSTab->zName, pWLoop->iTab);
+          }
+        }
+        sqlite3DebugPrintf("\n");
+      }
 #endif
       pWInfo->bStarUsed = 1;
 
@@ -5736,10 +5763,8 @@ static int computeMxChoice(WhereInfo *pWInfo){
           if( sqlite3WhereTrace & 0x80000 ){
             SrcItem *pDim = aFromTabs + pWLoop->iTab;
             sqlite3DebugPrintf(
-              "Increase SCAN cost of dimension %s(%d) of fact %s(%d) to %d\n",
-              pDim->zAlias ? pDim->zAlias: pDim->pSTab->zName, pWLoop->iTab,
-              pFactTab->zAlias ? pFactTab->zAlias : pFactTab->pSTab->zName,
-              iFromIdx, mxRun
+              "Increase SCAN cost of %s to %d\n",
+              pDim->zAlias ? pDim->zAlias: pDim->pSTab->zName, mxRun
             );
           }
           pWLoop->rStarDelta = mxRun - pWLoop->rRun;