From: drh <drh@noemail.net>
Date: Thu, 26 Oct 2017 20:04:28 +0000 (+0000)
Subject: Enhance the min/max optimization so that it works with indexes on
X-Git-Tag: version-3.22.0~229
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=47d9f83982e5996134fa1f4c744ff3192f1003f2;p=thirdparty%2Fsqlite.git

Enhance the min/max optimization so that it works with indexes on
expressions.

FossilOrigin-Name: 6caec9082b3ad6d3f89f6291084a8f5c80f296630e2e94bc764389ac1a47a833
---

diff --git a/manifest b/manifest
index 8c7e2d8801..f1127b40df 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Extra\s".selecttrace"\soutput\sfollowing\saggregate\sanalysis.\s\sNo\schanges\sto\nproduction\sbuilds.
-D 2017-10-26T18:43:19.787
+C Enhance\sthe\smin/max\soptimization\sso\sthat\sit\sworks\swith\sindexes\son\nexpressions.
+D 2017-10-26T20:04:28.629
 F Makefile.in e016061b23e60ac9ec27c65cb577292b6bde0307ca55abd874ab3487b3b1beb2
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 37740aba9c4bb359c627eadccf1cfd7be4f5f847078723777ea7763969e533b1
@@ -463,7 +463,7 @@ F src/printf.c 40aee47ae9be4bd3dbdc8968bd07fddc027be8edec8daddf24d3391d36698a1c
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 5a461643f294ec510ca615b67256fc3861e4c8eff5f29e5940491e70553b1955
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
-F src/select.c d055dc3a428ab2dd94ffdbaef50d90b41579be8ffe258591615d3d83bd859f7b
+F src/select.c 0b4c1ac59221c91c9f01c326105c1749874704a77310735c0417f3c3026a4f11
 F src/shell.c.in f13262c8778f0cd76bf8d9c01bbf5ef66842e6b14e1705cd60d86ab32a6ce69f
 F src/sqlite.h.in ab4f8a29d1580dfaeb6891fa1b83cff8229ba0daa56994707ceaca71495d9ab7
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -1044,7 +1044,7 @@ F test/memleak.test 10b9c6c57e19fc68c32941495e9ba1c50123f6e2
 F test/memsubsys1.test 9e7555a22173b8f1c96c281ce289b338fcba2abe8b157f8798ca195bbf1d347e
 F test/memsubsys2.test 3e4a8d0c05fd3e5fa92017c64666730a520c7e08
 F test/minmax.test 6751e87b409fe11b02e70a306d846fa544e25a41
-F test/minmax2.test b44bae787fc7b227597b01b0ca5575c7cb54d3bc
+F test/minmax2.test dae92964ac87c1d2ef978c582e81a95e11c00f1cbef68980bfb2abaf10315063
 F test/minmax3.test cc1e8b010136db0d01a6f2a29ba5a9f321034354
 F test/minmax4.test 936941484ebdceb8adec7c86b6cd9b6e5e897c1f
 F test/misc1.test 76737c259537586355f45e2a1e121b6e91b5476c4604ad5c53d1abfcb3acf786
@@ -1666,7 +1666,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e1faa7859451ee969f0ce02d2d4e4c54d0e2e018b37b8faf690e6b87593cce7d
-R d61bdf0ef8749a81bf4548782da0df22
+P 6fbf74ab3189b9cb20cf7cc8db0226eb935a8eab477cc83b8390492fcf2f1f76
+R c17176b8dc9ac053e5191ecbda77db6f
 U drh
-Z eef6957fcaef94fa72ebc9ad261c03d1
+Z 1bd9fa3ff01b6d52accac3363bceb595
diff --git a/manifest.uuid b/manifest.uuid
index 0db876cf23..41f1ba3965 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6fbf74ab3189b9cb20cf7cc8db0226eb935a8eab477cc83b8390492fcf2f1f76
\ No newline at end of file
+6caec9082b3ad6d3f89f6291084a8f5c80f296630e2e94bc764389ac1a47a833
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index 0f73c30f64..69ef06aeb5 100644
--- a/src/select.c
+++ b/src/select.c
@@ -3919,42 +3919,44 @@ static int pushDownWhereTerms(
 #endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
 
 /*
-** Based on the contents of the AggInfo structure indicated by the first
-** argument, this function checks if the following are true:
+** The pFunc is the only aggregate function in the query.  Check to see
+** if the query is a candidate for the min/max optimization. 
 **
-**    * the query contains just a single aggregate function,
-**    * the aggregate function is either min() or max(), and
-**    * the argument to the aggregate function is a column value.
+** If the query is a candidate for the min/max optimization, then set
+** *ppMinMax to be an ORDER BY clause to be used for the optimization
+** and return either WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX depending on
+** whether pFunc is a min() or max() function.
 **
-** If all of the above are true, then WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX
-** is returned as appropriate. Also, *ppMinMax is set to point to the 
-** list of arguments passed to the aggregate before returning.
+** If the query is not a candidate for the min/max optimization, return
+** WHERE_ORDERBY_NORMAL (which must be zero).
 **
-** Or, if the conditions above are not met, *ppMinMax is set to 0 and
-** WHERE_ORDERBY_NORMAL is returned.
+** This routine must be called after aggregate functions have been
+** located but before their arguments have been subjected to aggregate
+** analysis.
 */
-static u8 minMaxQuery(AggInfo *pAggInfo, ExprList **ppMinMax){
-  int eRet = WHERE_ORDERBY_NORMAL;          /* Return value */
-
-  *ppMinMax = 0;
-  if( pAggInfo->nFunc==1 ){
-    Expr *pExpr = pAggInfo->aFunc[0].pExpr; /* Aggregate function */
-    ExprList *pEList = pExpr->x.pList;      /* Arguments to agg function */
-
-    assert( pExpr->op==TK_AGG_FUNCTION );
-    if( pEList && pEList->nExpr==1 && pEList->a[0].pExpr->op==TK_AGG_COLUMN ){
-      const char *zFunc = pExpr->u.zToken;
-      if( sqlite3StrICmp(zFunc, "min")==0 ){
-        eRet = WHERE_ORDERBY_MIN;
-        *ppMinMax = pEList;
-      }else if( sqlite3StrICmp(zFunc, "max")==0 ){
-        eRet = WHERE_ORDERBY_MAX;
-        *ppMinMax = pEList;
-      }
-    }
+static u8 minMaxQuery(sqlite3 *db, Expr *pFunc, ExprList **ppMinMax){
+  int eRet = WHERE_ORDERBY_NORMAL;      /* Return value */
+  ExprList *pEList = pFunc->x.pList;    /* Arguments to agg function */
+  const char *zFunc;                    /* Name of aggregate function pFunc */
+  ExprList *pOrderBy;
+  u8 sortOrder;
+
+  assert( *ppMinMax==0 );
+  assert( pFunc->op==TK_AGG_FUNCTION );
+  if( pEList==0 || pEList->nExpr!=1 ) return eRet;
+  zFunc = pFunc->u.zToken;
+  if( sqlite3StrICmp(zFunc, "min")==0 ){
+    eRet = WHERE_ORDERBY_MIN;
+    sortOrder = SQLITE_SO_ASC;
+  }else if( sqlite3StrICmp(zFunc, "max")==0 ){
+    eRet = WHERE_ORDERBY_MAX;
+    sortOrder = SQLITE_SO_DESC;
+  }else{
+    return eRet;
   }
-
-  assert( *ppMinMax==0 || (*ppMinMax)->nExpr==1 );
+  *ppMinMax = pOrderBy = sqlite3ExprListDup(db, pEList, 0);
+  assert( pOrderBy!=0 || db->mallocFailed );
+  if( pOrderBy ) pOrderBy->a[0].sortOrder = sortOrder;
   return eRet;
 }
 
@@ -5135,6 +5137,8 @@ int sqlite3Select(
   AggInfo sAggInfo;      /* Information used by aggregate queries */
   int iEnd;              /* Address of the end of the query */
   sqlite3 *db;           /* The database connection */
+  ExprList *pMinMaxOrderBy = 0;  /* Added ORDER BY for min/max queries */
+  u8 minMaxFlag;                 /* Flag for min/max queries */
 
 #ifndef SQLITE_OMIT_EXPLAIN
   int iRestoreSelectId = pParse->iSelectId;
@@ -5651,6 +5655,11 @@ int sqlite3Select(
       sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
     }
     sAggInfo.nAccumulator = sAggInfo.nColumn;
+    if( p->pGroupBy==0 && p->pHaving==0 && sAggInfo.nFunc==1 ){
+      minMaxFlag = minMaxQuery(db, sAggInfo.aFunc[0].pExpr, &pMinMaxOrderBy);
+    }else{
+      minMaxFlag = WHERE_ORDERBY_NORMAL;
+    }
     for(i=0; i<sAggInfo.nFunc; i++){
       assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
       sNC.ncFlags |= NC_InAggFunc;
@@ -5906,7 +5915,6 @@ int sqlite3Select(
      
     } /* endif pGroupBy.  Begin aggregate queries without GROUP BY: */
     else {
-      ExprList *pDel = 0;
 #ifndef SQLITE_OMIT_BTREECOUNT
       Table *pTab;
       if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
@@ -5968,67 +5976,31 @@ int sqlite3Select(
       }else
 #endif /* SQLITE_OMIT_BTREECOUNT */
       {
-        /* Check if the query is of one of the following forms:
-        **
-        **   SELECT min(x) FROM ...
-        **   SELECT max(x) FROM ...
-        **
-        ** If it is, then ask the code in where.c to attempt to sort results
-        ** as if there was an "ORDER BY x" or "ORDER BY x DESC" clause. 
-        ** If where.c is able to produce results sorted in this order, then
-        ** add vdbe code to break out of the processing loop after the 
-        ** first iteration (since the first iteration of the loop is 
-        ** guaranteed to operate on the row with the minimum or maximum 
-        ** value of x, the only row required).
-        **
-        ** A special flag must be passed to sqlite3WhereBegin() to slightly
-        ** modify behavior as follows:
-        **
-        **   + If the query is a "SELECT min(x)", then the loop coded by
-        **     where.c should not iterate over any values with a NULL value
-        **     for x.
-        **
-        **   + The optimizer code in where.c (the thing that decides which
-        **     index or indices to use) should place a different priority on 
-        **     satisfying the 'ORDER BY' clause than it does in other cases.
-        **     Refer to code and comments in where.c for details.
-        */
-        ExprList *pMinMax = 0;
-        u8 flag = WHERE_ORDERBY_NORMAL;
-        
-        assert( p->pGroupBy==0 );
-        assert( flag==0 );
-        if( p->pHaving==0 ){
-          flag = minMaxQuery(&sAggInfo, &pMinMax);
-        }
-        assert( flag==0 || (pMinMax!=0 && pMinMax->nExpr==1) );
-
-        if( flag ){
-          pMinMax = sqlite3ExprListDup(db, pMinMax, 0);
-          pDel = pMinMax;
-          assert( db->mallocFailed || pMinMax!=0 );
-          if( !db->mallocFailed ){
-            pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN ?1:0;
-            pMinMax->a[0].pExpr->op = TK_COLUMN;
-          }
-        }
-  
         /* This case runs if the aggregate has no GROUP BY clause.  The
         ** processing is much simpler since there is only a single row
         ** of output.
         */
+        assert( p->pGroupBy==0 );
         resetAccumulator(pParse, &sAggInfo);
-        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMax, 0,flag,0);
+
+        /* If this query is a candidate for the min/max optimization, then
+        ** minMaxFlag will have been previously set to either
+        ** WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX and pMinMaxOrderBy will
+        ** be an appropriate ORDER BY expression for the optimization.
+        */
+        assert( minMaxFlag==WHERE_ORDERBY_NORMAL || pMinMaxOrderBy!=0 );
+        assert( pMinMaxOrderBy==0 || pMinMaxOrderBy->nExpr==1 );
+
+        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMaxOrderBy,
+                                   0, minMaxFlag, 0);
         if( pWInfo==0 ){
-          sqlite3ExprListDelete(db, pDel);
           goto select_end;
         }
         updateAccumulator(pParse, &sAggInfo);
-        assert( pMinMax==0 || pMinMax->nExpr==1 );
         if( sqlite3WhereIsOrdered(pWInfo)>0 ){
           sqlite3VdbeGoto(v, sqlite3WhereBreakLabel(pWInfo));
           VdbeComment((v, "%s() by index",
-                (flag==WHERE_ORDERBY_MIN?"min":"max")));
+                (minMaxFlag==WHERE_ORDERBY_MIN?"min":"max")));
         }
         sqlite3WhereEnd(pWInfo);
         finalizeAggFunctions(pParse, &sAggInfo);
@@ -6038,7 +6010,6 @@ int sqlite3Select(
       sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
       selectInnerLoop(pParse, p, -1, 0, 0, 
                       pDest, addrEnd, addrEnd);
-      sqlite3ExprListDelete(db, pDel);
     }
     sqlite3VdbeResolveLabel(v, addrEnd);
     
@@ -6070,7 +6041,7 @@ int sqlite3Select(
   */
 select_end:
   explainSetInteger(pParse->iSelectId, iRestoreSelectId);
-
+  sqlite3ExprListDelete(db, pMinMaxOrderBy);
   sqlite3DbFree(db, sAggInfo.aCol);
   sqlite3DbFree(db, sAggInfo.aFunc);
 #if SELECTTRACE_ENABLED
diff --git a/test/minmax2.test b/test/minmax2.test
index da8fec30ce..b6114f2e51 100644
--- a/test/minmax2.test
+++ b/test/minmax2.test
@@ -383,5 +383,39 @@ do_test minmax2-10.12 {
   }
 } {{} {}}
 
+# 2017-10-26.  Extend the min/max optimization to indexes on expressions
+#
+do_execsql_test minmax2-11.100 {
+  CREATE TABLE t11(a,b,c);
+  INSERT INTO t11(a,b,c) VALUES(1,10,5),(2,8,11),(3,1,4),(4,20,1),(5,16,4);
+  CREATE INDEX t11bc ON t11(b+c);
+  SELECT max(b+c) FROM t11;
+} {21}
+do_execsql_test minmax2-11.110 {
+  SELECT a, max(b+c) FROM t11;
+} {4 21}
+do_test minmax2-11.111 {
+  db eval {SELECT max(b+c) FROM t11}
+  db status step
+} {0}
+do_test minmax2-11.112 {
+  db eval {SELECT max(c+b) FROM t11}
+  db status step
+} {4}
+do_execsql_test minmax2-11.120 {
+  SELECT a, min(b+c) FROM t11;
+} {3 5}
+do_test minmax2-11.121 {
+  db eval {SELECT min(b+c) FROM t11}
+  db status step
+} {0}
+do_test minmax2-11.122 {
+  db eval {SELECT min(c+b) FROM t11}
+  db status step
+} {4}
+do_execsql_test minmax2-11.130 {
+  INSERT INTO t11(a,b,c) VALUES(6,NULL,0),(7,0,NULL);
+  SELECT a, min(b+c) FROM t11;
+} {3 5}
 
 finish_test