From: drh <drh@noemail.net>
Date: Thu, 27 Sep 2012 14:11:36 +0000 (+0000)
Subject: Enable ORDER BY clauses that span joins to be optimized out.
X-Git-Tag: version-3.7.15~112^2~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=32634d270ce9de65ac8a1cec14df671a477ce91c;p=thirdparty%2Fsqlite.git

Enable ORDER BY clauses that span joins to be optimized out.

FossilOrigin-Name: c29538f9b1ee4d4869999570604c9618ca0d08ac
---

diff --git a/manifest b/manifest
index 5f591e9ff6..a66358269a 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Further\stweaks\sto\sthe\squery\splanner\slogic\sin\spreparation\sfor\sadding\nORDER\sBY\sopt-out\sfor\sjoins.
-D 2012-09-27T12:05:09.522
+C Enable\sORDER\sBY\sclauses\sthat\sspan\sjoins\sto\sbe\soptimized\sout.
+D 2012-09-27T14:11:36.514
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5f4f26109f9d80829122e0e09f9cda008fa065fb
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -249,7 +249,7 @@ F src/vtab.c d8020c0a0e8ccc490ca449d7e665311b6e9f3ba9
 F src/wal.c 5acb3e7bbd31f10ba39acad9ce6b399055337a9d
 F src/wal.h 29c197540b19044e6cd73487017e5e47a1d3dac6
 F src/walker.c 3d75ba73de15e0f8cd0737643badbeb0e002f07b
-F src/where.c 67438c6192c5f777139e7abb642a9186a21a718d
+F src/where.c 36af33a92ccbf8b5be3bc7eae08a7f022afb60d8
 F test/8_3_names.test 631ea964a3edb091cf73c3b540f6bcfdb36ce823
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 0be144b453e0622a085fae8665c32f5676708e00
@@ -1016,7 +1016,7 @@ F tool/vdbe-compress.tcl f12c884766bd14277f4fcedcae07078011717381
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
 F tool/win/sqlite.vsix 67d8a99aceb56384a81b3f30d6c71743146d2cc9
-P 96496ddae12a239b30a1fc997fbea43e3a75bfe7
-R 57ad7fba1d5db0bb9191afb65acee747
+P 53efc10af990d3f293551f3cd8ef2f8be2d9d716
+R d9d746ad3fd7e5c77ffbaf4f5251f6f8
 U drh
-Z 58fdbd300662a0c1ec2665b77df5f795
+Z 769b41d4cd58dfa3626d0858103449b9
diff --git a/manifest.uuid b/manifest.uuid
index 2e377696fc..c7339ef5c5 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-53efc10af990d3f293551f3cd8ef2f8be2d9d716
\ No newline at end of file
+c29538f9b1ee4d4869999570604c9618ca0d08ac
\ No newline at end of file
diff --git a/src/where.c b/src/where.c
index 0405860c9a..ce5437a9f5 100644
--- a/src/where.c
+++ b/src/where.c
@@ -2863,17 +2863,67 @@ static int whereInScanEst(
 }
 #endif /* defined(SQLITE_ENABLE_STAT3) */
 
+/*
+** Check to see if column iCol of the table with cursor iTab will appear
+** in sorted order according to the current query plan.  Return true if
+** it will and false if not.  
+**
+** If *pbRev is initially 2 (meaning "unknown") then set *pbRev to the
+** sort order of iTab.iCol.  If *pbRev is 0 or 1 but does not match
+** the sort order of iTab.iCol, then consider the column to be unordered.
+*/
+static int isOrderedColumn(WhereBestIdx *p, int iTab, int iCol, int *pbRev){
+  int i, j;
+  WhereLevel *pLevel = &p->aLevel[p->i-1];
+  Index *pIdx;
+  u8 sortOrder;
+  for(i=p->i-1; i>=0; i--, pLevel--){
+    if( pLevel->iTabCur!=iTab ) continue;
+    if( (pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE))!=0 ){
+      if( iCol!=(-1) ) return 0;
+      sortOrder = 0;
+    }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      pIdx = pLevel->plan.u.pIdx;
+      for(j=0; j<pIdx->nColumn; j++){
+        if( iCol==pIdx->aiColumn[j] ) break;
+      }
+      if( j>=pIdx->nColumn ) return 0;
+      sortOrder = pIdx->aSortOrder[j];
+    }else{
+      if( iCol!=(-1) ) return 0;
+      sortOrder = 0;
+    }
+    if( (pLevel->plan.wsFlags & WHERE_REVERSE)!=0 ) sortOrder = 1 - sortOrder;
+    if( *pbRev==2 ){
+      *pbRev = sortOrder;
+      return 1;
+    }
+    return (*pbRev==sortOrder);
+  }
+  return 0;
+}
+
 /*
 ** pTerm is an == constraint.  Check to see if the other side of
 ** the == is a constant or a value that is guaranteed to be ordered
 ** by outer loops.  Return 1 if pTerm is ordered, and 0 if not.
 */
 static int isOrderedTerm(WhereBestIdx *p, WhereTerm *pTerm, int *pbRev){
+  Expr *pExpr = pTerm->pExpr;
+  assert( pExpr->op==TK_EQ );
+  assert( pExpr->pLeft!=0 && pExpr->pLeft->op==TK_COLUMN );
+  assert( pExpr->pRight!=0 );
   if( p->i==0 ){
     return 1;  /* All == are ordered in the outer loop */
   }
-
-
+  if( pTerm->prereqRight==0 ){
+    return 1;  /* RHS of the == is a constant */
+  }
+  if( pExpr->pRight->op==TK_COLUMN 
+   && isOrderedColumn(p, pExpr->pRight->iTable, pExpr->pRight->iColumn, pbRev)
+  ){
+    return 1;
+  }
 
   /* If we cannot prove that the constraint is ordered, assume it is not */
   return 0;