From: drh <drh@noemail.net>
Date: Fri, 21 Jun 2013 02:15:48 +0000 (+0000)
Subject: Only eliminate inner loops of a JOIN if they are the RHS of a LEFT JOIN
X-Git-Tag: version-3.8.0~133^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bc71b1d4536ce7842f80010049c69f5fd2806b3b;p=thirdparty%2Fsqlite.git

Only eliminate inner loops of a JOIN if they are the RHS of a LEFT JOIN
and if they give no more than a single result.  This appears to give correct
answers in all cases.

FossilOrigin-Name: d7a25cc79794817504ca1a4262008a68b2a4dece
---

diff --git a/manifest b/manifest
index 2d7ec778f6..a54bc73242 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Attempt\sto\sdisable\sinner\sloops\sof\sa\sjoin\sthat\sdo\snot\sgenerate\soutput.\nThis\sdoes\snot\swork,\ssince\sthe\sinner\sloops\smight\srun\szero\stimes\sand\sthus\ninhibit\sall\soutput.\s\sNeeds\sto\sbe\senhanced\sto\swork\sonly\sfor\sLEFT\sJOINs\nor\swhen\swe\sknow\sthat\sthe\sinner\sloop\swill\salways\srun\sat\sleast\sonce.
-D 2013-06-21T02:05:06.206
+C Only\seliminate\sinner\sloops\sof\sa\sJOIN\sif\sthey\sare\sthe\sRHS\sof\sa\sLEFT\sJOIN\nand\sif\sthey\sgive\sno\smore\sthan\sa\ssingle\sresult.\s\sThis\sappears\sto\sgive\scorrect\nanswers\sin\sall\scases.
+D 2013-06-21T02:15:48.306
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5e41da95d92656a5004b03d3576e8b226858a28e
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -289,7 +289,7 @@ F src/vtab.c b05e5f1f4902461ba9f5fc49bb7eb7c3a0741a83
 F src/wal.c 436bfceb141b9423c45119e68e444358ee0ed35d
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 4fa43583d0a84b48f93b1e88f11adf2065be4e73
-F src/where.c fc5293b54a70474c2b46e9df26c9e2803b152e68
+F src/where.c 0ca9544cca6e40550b970574a32055463650df12
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 45c0201e28045ad38a530b5a144b73cd4aa2cfd6
@@ -1096,7 +1096,7 @@ F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
 F tool/wherecosttest.c f407dc4c79786982a475261866a161cd007947ae
 F tool/win/sqlite.vsix 97894c2790eda7b5bce3cc79cb2a8ec2fde9b3ac
-P 2c2577e69ccb47f1af674a755e71221e2ca0b322
-R b2263c66dd8a59884ee45351c335261a
+P ca839723a21bb13d3e0666a672c15c6f3a267c2f
+R 6b62f4d6f88cb9d978862e981acfa473
 U drh
-Z 6fd83e64fe937f64082b799e88969f81
+Z b99e6e4ea8d5a45c0b5323f96846f0b0
diff --git a/manifest.uuid b/manifest.uuid
index b8cca3c3d8..32c308b877 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ca839723a21bb13d3e0666a672c15c6f3a267c2f
\ No newline at end of file
+d7a25cc79794817504ca1a4262008a68b2a4dece
\ No newline at end of file
diff --git a/src/where.c b/src/where.c
index 18b4a3782e..32fa61c7f0 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5794,16 +5794,16 @@ WhereInfo *sqlite3WhereBegin(
     if( pOrderBy ) tabUsed |= exprListTableUsage(pMaskSet, pOrderBy);
     while( pWInfo->nLevel>=2 ){
       pLoop = pWInfo->a[pWInfo->nLevel-1].pWLoop;
-      if( ((wctrlFlags & WHERE_WANT_DISTINCT)!=0
-           || (pLoop->wsFlags & WHERE_ONEROW)!=0)
-       && (tabUsed & pLoop->maskSelf)==0
+      if( (pWInfo->pTabList->a[pLoop->iTab].jointype & JT_LEFT)==0 ) break;
+      if( (wctrlFlags & WHERE_WANT_DISTINCT)==0
+       && (pLoop->wsFlags & WHERE_ONEROW)==0
       ){
-        WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
-        pWInfo->nLevel--;
-        nTabList--;
-      }else{
         break;
       }
+      if( (tabUsed & pLoop->maskSelf)!=0 ) break;
+      WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
+      pWInfo->nLevel--;
+      nTabList--;
     }
   }
   WHERETRACE(0xffff,("*** Optimizer Finished ***\n"));