Merge the sqlite3WhereBegin() simplification from trunk.

FossilOrigin-Name: 41ba2dfdd3a18671fc78d60935a16fa50f36af3d6481eff2ca9fba88e7093997

manifest

@@ -1,5 +1,5 @@
-C Merge\srecent\strunk\senhancements\sinto\sthe\sbloom-filter\sbranch.
+C Merge\sthe\ssqlite3WhereBegin()\ssimplification\sfrom\strunk.
-D 2021-12-03T16:02:05.551
+D 2021-12-03T19:10:17.141
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -637,7 +637,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c ed0398a7adf02c31e34aada42cc86c58f413a7afe5f741a5d373ad087abde028
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
-F src/where.c c04c4108028513cf2f264505f2bc3e861c2ed96985d7a5feead4cf76fe057dc1
+F src/where.c a0787ad0a3447685e553725dab50e52c9763b5f10e2506255713dbd736c89998
 F src/whereInt.h 83ae6f7d0fce8b5164d97698790e0005a909b3d06d73df86a4a6bb0d9411861e
 F src/wherecode.c 620e81077588a727876a86f87aab310c02fc4e4960691e48153d8a87ca1fa453
 F src/whereexpr.c 19394cb463003e9cc9305730b1508b8817a22bb7247170d81234b691a7f05b89
@@ -1933,7 +1933,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0864bfbf079a98beaa484911edb17c3dc728e78eca231d4247b282fd824cc098 8029e6bab508bf0b8ec1df00a829c5d4de2a84d66dc56b9ff03da879ceef7788
+P 11d97fb8be6b5155f38df130d7e828edd0f381e32f651458939b1cb9cb973fff 6225e9abcb0261fefca4a26530524ffc449f937f8ae1ece718af2c3c3d73d78d
-R 62eaa6fad42f4285b48b7186b5cb4970
+R 91b705f2730ed0122ffcaf8efbe0af73
 U drh
-Z 2d614121b81c56be6760e2166ceb6c54
+Z dab48a2f628412943ed7bfde21b0a086

manifest.uuid

@@ -1 +1 @@
-11d97fb8be6b5155f38df130d7e828edd0f381e32f651458939b1cb9cb973fff
+41ba2dfdd3a18671fc78d60935a16fa50f36af3d6481eff2ca9fba88e7093997

src/where.c

@@ -4751,6 +4751,96 @@ static void showAllWhereLoops(WhereInfo *pWInfo, WhereClause *pWC){
 # define WHERETRACE_ALL_LOOPS(W,C)
 #endif
 
+/* Attempt to omit tables from a join that do not affect the result.
+** For a table to not affect the result, the following must be true:
+**
+**   1) The query must not be an aggregate.
+**   2) The table must be the RHS of a LEFT JOIN.
+**   3) Either the query must be DISTINCT, or else the ON or USING clause
+**      must contain a constraint that limits the scan of the table to 
+**      at most a single row.
+**   4) The table must not be referenced by any part of the query apart
+**      from its own USING or ON clause.
+**
+** For example, given:
+**
+**     CREATE TABLE t1(ipk INTEGER PRIMARY KEY, v1);
+**     CREATE TABLE t2(ipk INTEGER PRIMARY KEY, v2);
+**     CREATE TABLE t3(ipk INTEGER PRIMARY KEY, v3);
+**
+** then table t2 can be omitted from the following:
+**
+**     SELECT v1, v3 FROM t1 
+**       LEFT JOIN t2 ON (t1.ipk=t2.ipk)
+**       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
+**
+** or from:
+**
+**     SELECT DISTINCT v1, v3 FROM t1 
+**       LEFT JOIN t2
+**       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
+*/
+static SQLITE_NOINLINE Bitmask whereOmitNoopJoin(
+  WhereInfo *pWInfo,
+  Bitmask notReady
+){
+  int i;
+  Bitmask tabUsed;
+
+  /* Preconditions checked by the caller */
+  assert( pWInfo->nLevel>=2 );
+  assert( OptimizationEnabled(pWInfo->pParse->db, SQLITE_OmitNoopJoin) );
+
+  /* These two preconditions checked by the caller combine to guarantee
+  ** condition (1) of the header comment */
+  assert( pWInfo->pResultSet!=0 );
+  assert( 0==(pWInfo->wctrlFlags & WHERE_AGG_DISTINCT) );
+
+  tabUsed = sqlite3WhereExprListUsage(&pWInfo->sMaskSet, pWInfo->pResultSet);
+  if( pWInfo->pOrderBy ){
+    tabUsed |= sqlite3WhereExprListUsage(&pWInfo->sMaskSet, pWInfo->pOrderBy);
+  }
+  for(i=pWInfo->nLevel-1; i>=1; i--){
+    WhereTerm *pTerm, *pEnd;
+    SrcItem *pItem;
+    WhereLoop *pLoop;
+    pLoop = pWInfo->a[i].pWLoop;
+    pItem = &pWInfo->pTabList->a[pLoop->iTab];
+    if( (pItem->fg.jointype & JT_LEFT)==0 ) continue;
+    if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)==0
+     && (pLoop->wsFlags & WHERE_ONEROW)==0
+    ){
+      continue;
+    }
+    if( (tabUsed & pLoop->maskSelf)!=0 ) continue;
+    pEnd = pWInfo->sWC.a + pWInfo->sWC.nTerm;
+    for(pTerm=pWInfo->sWC.a; pTerm<pEnd; pTerm++){
+      if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
+        if( !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
+         || pTerm->pExpr->iRightJoinTable!=pItem->iCursor
+        ){
+          break;
+        }
+      }
+    }
+    if( pTerm<pEnd ) continue;
+    WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
+    notReady &= ~pLoop->maskSelf;
+    for(pTerm=pWInfo->sWC.a; pTerm<pEnd; pTerm++){
+      if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
+        pTerm->wtFlags |= TERM_CODED;
+      }
+    }
+    if( i!=pWInfo->nLevel-1 ){
+      int nByte = (pWInfo->nLevel-1-i) * sizeof(WhereLevel);
+      memmove(&pWInfo->a[i], &pWInfo->a[i+1], nByte);
+    }
+    pWInfo->nLevel--;
+    assert( pWInfo->nLevel>0 );
+  }
+  return notReady;
+}
+
 /*
 ** Generate the beginning of the loop used for WHERE clause processing.
 ** The return value is a pointer to an opaque structure that contains
@@ -5119,34 +5209,15 @@ WhereInfo *sqlite3WhereBegin(
   }
 #endif
 
-  /* Attempt to omit tables from the join that do not affect the result.
+  /* Attempt to omit tables from a join that do not affect the result.
-  ** For a table to not affect the result, the following must be true:
+  ** See the comment on whereOmitNoopJoin() for further information.
   **
-  **   1) The query must not be an aggregate.
+  ** This query optimization is factored out into a separate "no-inline"
-  **   2) The table must be the RHS of a LEFT JOIN.
+  ** procedure to keep the sqlite3WhereBegin() procedure from becoming
-  **   3) Either the query must be DISTINCT, or else the ON or USING clause
+  ** too large.  If sqlite3WhereBegin() becomes too large, that prevents
-  **      must contain a constraint that limits the scan of the table to 
+  ** some C-compiler optimizers from in-lining the 
-  **      at most a single row.
+  ** sqlite3WhereCodeOneLoopStart() procedure, and it is important to
-  **   4) The table must not be referenced by any part of the query apart
+  ** in-line sqlite3WhereCodeOneLoopStart() for performance reasons.
-  **      from its own USING or ON clause.
-  **
-  ** For example, given:
-  **
-  **     CREATE TABLE t1(ipk INTEGER PRIMARY KEY, v1);
-  **     CREATE TABLE t2(ipk INTEGER PRIMARY KEY, v2);
-  **     CREATE TABLE t3(ipk INTEGER PRIMARY KEY, v3);
-  **
-  ** then table t2 can be omitted from the following:
-  **
-  **     SELECT v1, v3 FROM t1 
-  **       LEFT JOIN t2 ON (t1.ipk=t2.ipk)
-  **       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
-  **
-  ** or from:
-  **
-  **     SELECT DISTINCT v1, v3 FROM t1 
-  **       LEFT JOIN t2
-  **       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
   */
   notReady = ~(Bitmask)0;
   if( pWInfo->nLevel>=2
@@ -5154,49 +5225,11 @@ WhereInfo *sqlite3WhereBegin(
    && 0==(wctrlFlags & WHERE_AGG_DISTINCT)  /* condition (1) above */
    && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
   ){
-    int i;
+    notReady = whereOmitNoopJoin(pWInfo, notReady);
-    Bitmask tabUsed = sqlite3WhereExprListUsage(pMaskSet, pResultSet);
+    nTabList = pWInfo->nLevel;
-    if( sWLB.pOrderBy ){
+    assert( nTabList>0 );
-      tabUsed |= sqlite3WhereExprListUsage(pMaskSet, sWLB.pOrderBy);
-    }
-    for(i=pWInfo->nLevel-1; i>=1; i--){
-      WhereTerm *pTerm, *pEnd;
-      SrcItem *pItem;
-      pLoop = pWInfo->a[i].pWLoop;
-      pItem = &pWInfo->pTabList->a[pLoop->iTab];
-      if( (pItem->fg.jointype & JT_LEFT)==0 ) continue;
-      if( (wctrlFlags & WHERE_WANT_DISTINCT)==0
-       && (pLoop->wsFlags & WHERE_ONEROW)==0
-      ){
-        continue;
-      }
-      if( (tabUsed & pLoop->maskSelf)!=0 ) continue;
-      pEnd = sWLB.pWC->a + sWLB.pWC->nTerm;
-      for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
-        if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
-          if( !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
-           || pTerm->pExpr->iRightJoinTable!=pItem->iCursor
-          ){
-            break;
-          }
-        }
-      }
-      if( pTerm<pEnd ) continue;
-      WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
-      notReady &= ~pLoop->maskSelf;
-      for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
-        if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
-          pTerm->wtFlags |= TERM_CODED;
-        }
-      }
-      if( i!=pWInfo->nLevel-1 ){
-        int nByte = (pWInfo->nLevel-1-i) * sizeof(WhereLevel);
-        memmove(&pWInfo->a[i], &pWInfo->a[i+1], nByte);
-      }
-      pWInfo->nLevel--;
-      nTabList--;
-    }
   }
+
 #if defined(WHERETRACE_ENABLED)
   if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
     sqlite3DebugPrintf("---- WHERE clause at end of analysis:\n");