From: drh <>
Date: Sat, 22 Oct 2022 20:13:46 +0000 (+0000)
Subject: Enhance the query planner with the ability to discern when an index is
X-Git-Tag: version-3.40.0~111^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=54cc766b418a0cab68cf21cbbf37872d55a654c6;p=thirdparty%2Fsqlite.git

Enhance the query planner with the ability to discern when an index is
covering even when it indexes columns well beyond the 63rd column.

FossilOrigin-Name: 1390417be45dd84e9118f6e761f23b8ff7476d26411e165bbaab678881e4eadd
---

diff --git a/manifest b/manifest
index 409ea22b91..9528ef1337 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C This\sbranch\sattempts\sto\simprove\sthe\sdetection\sof\scovering\sindexes.\s\sThis\nfirst\scheck-in\smerely\simproves\sa\sparameter\sname\sto\ssqlite3WhereBegin()\sto\nbe\smore\sdescriptive\sof\swhat\sit\scontains,\sand\sensures\sthat\sa\ssubroutine\sis\nnot\sinlines\sso\sthat\ssqlite3WhereBegin()\sruns\sslightly\sfaster.
-D 2022-10-22T14:16:02.784
+C Enhance\sthe\squery\splanner\swith\sthe\sability\sto\sdiscern\swhen\san\sindex\sis\ncovering\seven\swhen\sit\sindexes\scolumns\swell\sbeyond\sthe\s63rd\scolumn.
+D 2022-10-22T20:13:46.151
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -625,7 +625,7 @@ F src/shell.c.in 6a9e15cb9fc3cd13d3647d4d9714c0d4d4a65e7f49228c2aafca910ed08d577
 F src/sqlite.h.in d9c8a6243fc0a1c270d69db33758e34b810af3462f9bc5b4af113b347e07c69d
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 5336beea1868d99d2f62e628dbea55e97267dbff8193291ab175e960c5df9141
-F src/sqliteInt.h 36f456f599a1bda4287ece61f3a9305b0b8d90ff49017a47a981cda5721a7ce0
+F src/sqliteInt.h 18590a040a47718b82cfdfd7a22ba03bfc6f278be4771a160039538279f3c17a
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 160c445d7d28c984a0eae38c144f6419311ed3eace59b44ac6dafc20db4af749
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -707,7 +707,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c b9df133a705093da8977da5eb202eaadb844839f1c7297c08d33471f5491843d
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
-F src/where.c 0e2d1630a0894b61e2dc6a20a83eaffa5b05e2680fba03902abf332d9573b522
+F src/where.c 658d7890809d20cd879621608cb8a6da19d7b4e00bbdbc175952c16ddaef4178
 F src/whereInt.h df0c79388c0b71b4a91f480d02791679fe0345d40410435c541c8893e95a4d3f
 F src/wherecode.c 133a94f82858787217d073143617df19e4a6a7d0b771a1519f957608109ad5a5
 F src/whereexpr.c a98e498cb7b6d033bf2ee7c04876ccf7b0b4d46e7f6510d6b458a411a4b27fa5
@@ -2036,11 +2036,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P d96f6cc8475ae5509b8bff2db75e3c6f69a214d58d8979fbc0162ae488a040dc
-R d1d7bec4f98c1ae80c81ea353f1cf097
-T *branch * covering-index-enh
-T *sym-covering-index-enh *
-T -sym-trunk *
+P cadf5f6bb1ce0492ef858ada476288e8057afd3609caa18b09c818d3845d7244
+R 505ea793a261a3784aaa7cb5127ecad5
 U drh
-Z 4413d5327beb9bbaff2921e04536c2c1
+Z 202e57f8058bf0a039d2caefddb8daa7
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 0ce3e4314f..d6cafbbfe6 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-cadf5f6bb1ce0492ef858ada476288e8057afd3609caa18b09c818d3845d7244
\ No newline at end of file
+1390417be45dd84e9118f6e761f23b8ff7476d26411e165bbaab678881e4eadd
\ No newline at end of file
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index ea75eb2769..04f8204d2a 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1255,6 +1255,7 @@ typedef struct With With;
 #define MASKBIT32(n)  (((unsigned int)1)<<(n))
 #define SMASKBIT32(n) ((n)<=31?((unsigned int)1)<<(n):0)
 #define ALLBITS       ((Bitmask)-1)
+#define TOPBIT        (((Bitmask)1)<<(BMS-1))
 
 /* A VList object records a mapping between parameters/variables/wildcards
 ** in the SQL statement (such as $abc, @pqr, or :xyz) and the integer
@@ -4091,13 +4092,13 @@ struct Walker {
     struct RefSrcList *pRefSrcList;           /* sqlite3ReferencesSrcList() */
     int *aiCol;                               /* array of column indexes */
     struct IdxCover *pIdxCover;               /* Check for index coverage */
-    struct IdxExprTrans *pIdxTrans;           /* Convert idxed expr to column */
     ExprList *pGroupBy;                       /* GROUP BY clause */
     Select *pSelect;                          /* HAVING to WHERE clause ctx */
     struct WindowRewrite *pRewrite;           /* Window rewrite context */
     struct WhereConst *pConst;                /* WHERE clause constants */
     struct RenameCtx *pRename;                /* RENAME COLUMN context */
     struct Table *pTab;                       /* Table of generated column */
+    struct CoveringIndexCheck *pCovIdxCk;     /* Check for covering index */
     SrcItem *pSrcItem;                        /* A single FROM clause item */
     DbFixer *pFix;
   } u;
diff --git a/src/where.c b/src/where.c
index 88aefd86ed..ff63098159 100644
--- a/src/where.c
+++ b/src/where.c
@@ -3247,6 +3247,94 @@ static int whereUsablePartialIndex(
   return 0;
 }
 
+/*
+** Structure passed to the whereIsCoveringIndex Walker callback.
+*/
+struct CoveringIndexCheck {
+  Index *pIdx;       /* The index */
+  int iTabCur;       /* Cursor number for the corresponding table */
+};
+
+/*
+** Information passed in is pWalk->u.pCovIdxCk.  Call is pCk.
+**
+** If the Expr node references the table with cursor pCk->iTabCur, then
+** make sure that column is covered by the index pCk->pIdx.  We know that
+** all columns less than 63 (really BMS-1) are covered, so we don't need
+** to check them.  But we do need to check any column at 63 or greater.
+**
+** If the index does not cover the column, then set pWalk->eCode to 
+** non-zero and return WRC_Abort to stop the search.
+**
+** If this node does not disprove that the index can be a covering index,
+** then just return WRC_Continue, to continue the search.
+*/
+static int whereIsCoveringIndexWalkCallback(Walker *pWalk, Expr *pExpr){
+  int i;                  /* Loop counter */
+  const Index *pIdx;      /* The index of interest */
+  const i16 *aiColumn;    /* Columns contained in the index */
+  u16 nColumn;            /* Number of columns in the index */
+  if( pExpr->op!=TK_COLUMN ) return WRC_Continue;
+  if( pExpr->iColumn<(BMS-1) ) return WRC_Continue;
+  if( pExpr->iTable!=pWalk->u.pCovIdxCk->iTabCur ) return WRC_Continue;
+  pIdx = pWalk->u.pCovIdxCk->pIdx;
+  aiColumn = pIdx->aiColumn;
+  nColumn = pIdx->nColumn;
+  for(i=0; i<nColumn; i++){
+    if( aiColumn[i]==pExpr->iColumn ) return WRC_Continue;
+  }
+  pWalk->eCode = 1;
+  return WRC_Abort;
+}
+
+
+/*
+** pIdx is an index that covers all of the low-number columns used by
+** pWInfo->pSelect (columns from 0 through 62).  But there are columns
+** in pWInfo->pSelect beyond 62.  This routine tries to answer the question
+** of whether pIdx covers *all* columns in the query.
+**
+** Return 0 if pIdx is a covering index.   Return non-zero if pIdx is
+** not a covering index or if we are unable to determine if pIdx is a
+** covering index.
+**
+** This routine is an optimization.  It is always safe to return non-zero.
+** But returning zero when non-zero should have been returned can lead to
+** incorrect bytecode and assertion faults.
+*/
+static SQLITE_NOINLINE u32 whereIsCoveringIndex(
+  WhereInfo *pWInfo,     /* The WHERE clause context */
+  Index *pIdx,           /* Index that is being tested */
+  int iTabCur            /* Cursor for the table being indexed */
+){
+  int i;
+  struct CoveringIndexCheck ck;
+  Walker w;
+  if( pWInfo->pSelect==0 ){
+    /* We don't have access to the full query, so we cannot check to see
+    ** if pIdx is covering.  Assume it is not. */
+    return 1;
+  }
+  for(i=0; i<pIdx->nColumn; i++){
+    if( pIdx->aiColumn[i]>=BMS-1 ) break;
+  }
+  if( i>=pIdx->nColumn ){
+    /* pIdx does not index any columns greater than 62, but we know from
+    ** colMask that columns greater than 62 are used, so this is not a
+    ** covering index */
+    return 1;
+  }
+  ck.pIdx = pIdx;
+  ck.iTabCur = iTabCur;
+  memset(&w, 0, sizeof(w));
+  w.xExprCallback = whereIsCoveringIndexWalkCallback;
+  w.xSelectCallback = sqlite3SelectWalkNoop;
+  w.u.pCovIdxCk = &ck;
+  w.eCode = 0;
+  sqlite3WalkSelect(&w, pWInfo->pSelect);
+  return w.eCode;
+}
+
 /*
 ** Add all WhereLoop objects for a single table of the join where the table
 ** is identified by pBuilder->pNew->iTab.  That table is guaranteed to be
@@ -3464,6 +3552,9 @@ static int whereLoopAddBtree(
         m = 0;
       }else{
         m = pSrc->colUsed & pProbe->colNotIdxed;
+        if( m==TOPBIT ){
+          m = whereIsCoveringIndex(pWInfo, pProbe, pSrc->iCursor);
+        }
         pNew->wsFlags = (m==0) ? (WHERE_IDX_ONLY|WHERE_INDEXED) : WHERE_INDEXED;
       }