From: drh <>
Date: Wed, 21 Sep 2022 18:21:31 +0000 (+0000)
Subject: Reduced and improved comments on the constraintCompatibleWithOuterJoin()
X-Git-Tag: version-3.40.0~197
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f333370e1ff64b27b8e578127414cce6fb37f7d6;p=thirdparty%2Fsqlite.git

Reduced and improved comments on the constraintCompatibleWithOuterJoin()
function.

FossilOrigin-Name: 38aaf26e082bd95df6b64df43e1772fe6e20c4eb71307dcd97559cac7f11f8f1
---

diff --git a/manifest b/manifest
index 7db55b50f8..d10a20caee 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C The\sRIGHT\sJOIN\slogic\sadded\sto\sversion\s3.39.0\sadded\sa\snew\srestriction\son\sthe\nquery\sflattener\swhich\sresulted\sin\sa\sperformance\sregression\sfor\ssome\squeries,\nas\sdocumented\sby\s[forum:/forumpost/96b9e5709cf47cda|forum\spost\s96b9e5709cf47cda].\nThis\schange\sremoves\sthat\srestriction\s(thus\srestoring\sperformance)\sand\sfixes\sthe\nproblem\sthat\sRIGHT\sJOIN\swas\shaving\sin\sa\sdifferent\sway.
-D 2022-09-21T09:54:41.195
+C Reduced\sand\simproved\scomments\son\sthe\sconstraintCompatibleWithOuterJoin()\nfunction.
+D 2022-09-21T18:21:31.342
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -675,7 +675,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c b9df133a705093da8977da5eb202eaadb844839f1c7297c08d33471f5491843d
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
-F src/where.c 3774d9831a6f4ac81f201fa9e2ec1bb40c99b7207dce7663c2e39fb73cc1bfd5
+F src/where.c 63e712bcad47f70e94c2150976cd7da5040933699e3938d4189d064acbe40891
 F src/whereInt.h 70cd30de9ed784aa33fa6bd1245f060617de7a00d992469b6d8e419eed915743
 F src/wherecode.c 6bb1cf9d0a4e3e04dab0bf0ea4a8d936a0dcc05a7e2207beeda6c61aea6dd341
 F src/whereexpr.c 55a39f42aaf982574fbf52906371a84cceed98a994422198dfd03db4fce4cc46
@@ -2000,9 +2000,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 8d8c124349d2a25200ace9a60d76751594b722468ad0c39d927a5d2c6e2464e0 c7fbc9b0453050e2746af27e3a11e0c3701bef8c56da8e19173242c6ea3aff8b
-R ffb250842cc4325c51d9fb2f2a7cd199
-T +closed c7fbc9b0453050e2746af27e3a11e0c3701bef8c56da8e19173242c6ea3aff8b
+P 501609eddf2a46d51e8cd56477a22d4df142a166e78fe4322c0db11d1eed6687
+R 5d32b5cf2b23f775eb14de7cc8da03e5
 U drh
-Z c4277c5174933f302dd59d96a8e6bf4e
+Z 712cc37fc63bdeb87733f2b1fa708ae7
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index c74cd3d3de..065a0d4be2 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-501609eddf2a46d51e8cd56477a22d4df142a166e78fe4322c0db11d1eed6687
\ No newline at end of file
+38aaf26e082bd95df6b64df43e1772fe6e20c4eb71307dcd97559cac7f11f8f1
\ No newline at end of file
diff --git a/src/where.c b/src/where.c
index 5811d830d1..b0c0ea7d4e 100644
--- a/src/where.c
+++ b/src/where.c
@@ -750,6 +750,11 @@ static void whereTraceIndexInfoOutputs(sqlite3_index_info *p){
 ** pTerm must be EP_OuterON if pSrc is the right operand of an
 ** outer join.  pTerm can be either EP_OuterON or EP_InnerON if pSrc
 ** is the left operand of a RIGHT join.
+**
+** See https://sqlite.org/forum/forumpost/206d99a16dd9212f
+** for an example of a WHERE clause constraints that may not be used on
+** the right table of a RIGHT JOIN because the constraint implies a
+** not-NULL condition on the left table of the RIGHT JOIN.
 */
 static int constraintCompatibleWithOuterJoin(
   const WhereTerm *pTerm,       /* WHERE clause term to check */
@@ -793,7 +798,7 @@ static int termCanDriveIndex(
   if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
    && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
   ){
-    return 0;
+    return 0;  /* See https://sqlite.org/forum/forumpost/51e6959f61 */
   }
   if( (pTerm->prereqRight & notReady)!=0 ) return 0;
   assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
@@ -1205,11 +1210,6 @@ static sqlite3_index_info *allocateIndexInfo(
     assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
     assert( pTerm->u.x.leftColumn>=XN_ROWID );
     assert( pTerm->u.x.leftColumn<pTab->nCol );
-
-    /* tag-20191211-002: WHERE-clause constraints are not useful to the
-    ** right-hand table of a LEFT JOIN nor to the either table of a
-    ** RIGHT JOIN.  See tag-20191211-001 for the
-    ** equivalent restriction for ordinary tables. */
     if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
      && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
     ){
@@ -2871,25 +2871,11 @@ static int whereLoopAddBtreeIndex(
     ** to mix with a lower range bound from some other source */
     if( pTerm->wtFlags & TERM_LIKEOPT && pTerm->eOperator==WO_LT ) continue;
 
-    /* tag-20191211-001:  Do not allow constraints from the WHERE clause to
-    ** be used by the right table of a LEFT JOIN nor by the left table of a
-    ** RIGHT JOIN.  Only constraints in the ON clause are allowed.
-    ** See tag-20191211-002 for the vtab equivalent.  
-    **
-    ** 2022-06-06: See https://sqlite.org/forum/forumpost/206d99a16dd9212f
-    ** for an example of a WHERE clause constraints that may not be used on
-    ** the right table of a RIGHT JOIN because the constraint implies a
-    ** not-NULL condition on the left table of the RIGHT JOIN.
-    **
-    ** 2022-06-10: The same condition applies to termCanDriveIndex() above.
-    ** https://sqlite.org/forum/forumpost/51e6959f61
-    */
     if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
      && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
     ){
       continue;
     }
-
     if( IsUniqueIndex(pProbe) && saved_nEq==pProbe->nKeyCol-1 ){
       pBuilder->bldFlags1 |= SQLITE_BLDF1_UNIQUE;
     }else{