From 6bfc167a67586d465ed995ae6dd3216967fc83c6 Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Thu, 14 Jan 2021 20:50:40 +0000
Subject: [PATCH 01/13] Allow the planner to convert an EXISTS(SELECT...)
 expression in a WHERE clause to the equivalent IN(...) expression in
 situations where this is possible and advantageous.

FossilOrigin-Name: 9f90a88221d0694951c353e58efce342eb0b868b8ca6a4469c8205e5c7855b24
---
 manifest        |  17 ++--
 manifest.uuid   |   2 +-
 src/whereexpr.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 211 insertions(+), 8 deletions(-)

diff --git a/manifest b/manifest
index b050b37ce0..a99b42e9cc 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C cli:\sOmit\ssurplus\swhitespace\sat\sthe\send\sof\slines\sin\s.explain\soutput.
-D 2021-01-13T12:59:20.834
+C Allow\sthe\splanner\sto\sconvert\san\sEXISTS(SELECT...)\sexpression\sin\sa\sWHERE\sclause\sto\sthe\sequivalent\sIN(...)\sexpression\sin\ssituations\swhere\sthis\sis\spossible\sand\sadvantageous.
+D 2021-01-14T20:50:40.571
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 3d31871d03906312d7d71a9c0b28c97bcbaead7606dfc15f9b3d080b18702385
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 3a463e156ea388083c501502229c2c7f4f5c6b5330ea59bdf40d6eb6e155a25f
+F src/whereexpr.c e48e3edea45b4afabbf6f6ece9647734c828a20c49a8cc780ff4d69b42f55fa4
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1895,7 +1895,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P db0ecfe66433f8915b6eb16d3735a4a0d0f8e0bbc395bc9c1364387506fc4657
-R 2ad612629a79dbad03e8b7f173945d59
-U drh
-Z f407a95e341e109313c0922f7d2a229b
+P 11e4eb095746602961a178044809a68a77ba7b367596997bef726e54062423d9
+R 1a9ea60bc9bb7dab69ccea9e0b8c40d8
+T *branch * exists-to-in
+T *sym-exists-to-in *
+T -sym-trunk *
+U dan
+Z d4d95c9878f460cd53a2ce8ada6afd2a
diff --git a/manifest.uuid b/manifest.uuid
index ccaf3daab6..e8520659ef 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-11e4eb095746602961a178044809a68a77ba7b367596997bef726e54062423d9
\ No newline at end of file
+9f90a88221d0694951c353e58efce342eb0b868b8ca6a4469c8205e5c7855b24
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index a77eb36106..9326a57fcb 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1007,6 +1007,202 @@ static int exprMightBeIndexed(
   return exprMightBeIndexed2(pFrom,mPrereq,aiCurCol,pExpr);
 }
 
+/*
+** Expression callback for exprUsesSrclist().
+*/
+static int exprUsesSrclistCb(Walker *p, Expr *pExpr){
+  if( pExpr->op==TK_COLUMN ){
+    SrcList *pSrc = p->u.pSrcList;
+    int iCsr = pExpr->iTable;
+    int ii;
+    for(ii=0; ii<pSrc->nSrc; ii++){
+      if( pSrc->a[ii].iCursor==iCsr ){
+        return p->eCode ? WRC_Abort : WRC_Continue;
+      }
+    }
+    return p->eCode ? WRC_Continue : WRC_Abort;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Select callback for exprUsesSrclist().
+*/
+static int exprUsesSrclistSelectCb(Walker *p, Select *pSelect){
+  return WRC_Abort;
+}
+
+/*
+** This function always returns true if expression pExpr contains
+** a sub-select.
+**
+** If there is no sub-select and bUses is 1, then true is returned
+** if the expression contains at least one TK_COLUMN node that refers
+** to a table in pSrc.
+**
+** Or, if there is no sub-select and bUses is 0, then true is returned
+** if the expression contains at least one TK_COLUMN node that refers
+** to a table that is not in pSrc.
+*/
+static int exprUsesSrclist(SrcList *pSrc, Expr *pExpr, int bUses){
+  Walker sWalker;
+  memset(&sWalker, 0, sizeof(Walker));
+  sWalker.eCode = bUses;
+  sWalker.u.pSrcList = pSrc;
+  sWalker.xExprCallback = exprUsesSrclistCb;
+  sWalker.xSelectCallback = exprUsesSrclistSelectCb;
+  return (sqlite3WalkExpr(&sWalker, pExpr)==WRC_Abort);
+}
+
+struct ExistsToInCtx {
+  SrcList *pSrc;
+  Expr *pInLhs;
+  Expr *pEq;
+  Expr **ppAnd;
+  Expr **ppParent;
+};
+
+static int exprExistsToInIter(
+  struct ExistsToInCtx *p, 
+  Expr *pExpr, 
+  Expr **ppExpr
+){
+  assert( ppExpr==0 || *ppExpr==pExpr );
+  switch( pExpr->op ){
+    case TK_AND:
+      p->ppParent = ppExpr;
+      if( exprExistsToInIter(p, pExpr->pLeft, &pExpr->pLeft) ) return 1;
+      p->ppParent = ppExpr;
+      if( exprExistsToInIter(p, pExpr->pRight, &pExpr->pRight) ) return 1;
+      break;
+    case TK_EQ: {
+      int bLeft = exprUsesSrclist(p->pSrc, pExpr->pLeft, 0);
+      int bRight = exprUsesSrclist(p->pSrc, pExpr->pRight, 0);
+      if( bLeft || bRight ){
+        if( (bLeft && bRight) || p->pInLhs ) return 1;
+        p->pInLhs = bLeft ? pExpr->pLeft : pExpr->pRight;
+        p->pEq = pExpr;
+        p->ppAnd = p->ppParent;
+        if( exprUsesSrclist(p->pSrc, p->pInLhs, 1) ) return 1;
+      }
+      break;
+    }
+    default:
+      if( exprUsesSrclist(p->pSrc, pExpr, 0) ){
+        return 1;
+      }
+      break;
+  }
+
+  return 0;
+}
+
+static Expr *exprAnalyzeExistsFindEq(
+  SrcList *pSrc,
+  Expr *pWhere,                   /* WHERE clause to traverse */
+  Expr **ppEq,                    /* OUT: == node from WHERE clause */
+  Expr ***pppAnd                  /* OUT: Pointer to parent of ==, if any */
+){
+  struct ExistsToInCtx ctx;
+  memset(&ctx, 0, sizeof(ctx));
+  ctx.pSrc = pSrc;
+  if( exprExistsToInIter(&ctx, pWhere, 0) ){
+    return 0;
+  }
+  if( ppEq ) *ppEq = ctx.pEq;
+  if( pppAnd ) *pppAnd = ctx.ppAnd;
+  return ctx.pInLhs;
+}
+
+/*
+** Term idxTerm of the WHERE clause passed as the second argument is an
+** EXISTS expression with a correlated SELECT statement on the RHS.
+** This function analyzes the SELECT statement, and if possible adds an
+** equivalent "? IN(SELECT...)" virtual term to the WHERE clause. 
+**
+** For an EXISTS term such as the following:
+**
+**     EXISTS (SELECT ... FROM <srclist> WHERE <e1> = <e2> AND <e3>)
+**
+** The virtual IN() term added is:
+**
+**     <e1> IN (SELECT <e2> FROM <srclist> WHERE <e3>)
+**
+** The virtual term is only added if the following conditions are met:
+**
+**     1. The sub-select must not be an aggregate or use window functions,
+**
+**     2. The sub-select must not be a compound SELECT,
+**
+**     3. Expression <e1> must refer to at least one column from the outer
+**        query, and must not refer to any column from the inner query 
+**        (i.e. from <srclist>).
+**
+**     4. <e2> and <e3> must not refer to any values from the outer query.
+**        In other words, once <e1> has been removed, the inner query
+**        must not be correlated.
+**
+*/
+static void exprAnalyzeExists(
+  SrcList *pSrc,            /* the FROM clause */
+  WhereClause *pWC,         /* the WHERE clause */
+  int idxTerm               /* Index of the term to be analyzed */
+){
+  Parse *pParse = pWC->pWInfo->pParse;
+  WhereTerm *pTerm = &pWC->a[idxTerm];
+  Expr *pExpr = pTerm->pExpr;
+  Select *pSel = pExpr->x.pSelect;
+  Expr *pDup = 0;
+  Expr *pEq = 0;
+  Expr *pRet = 0;
+  Expr *pInLhs = 0;
+  Expr **ppAnd = 0;
+  int idxNew;
+
+  assert( pExpr->op==TK_EXISTS );
+  assert( (pExpr->flags & EP_VarSelect) && (pExpr->flags & EP_xIsSelect) );
+
+  if( (pSel->selFlags & SF_Aggregate) || pSel->pWin ) return;
+  if( pSel->pPrior ) return;
+  if( pSel->pWhere==0 ) return;
+  if( 0==exprAnalyzeExistsFindEq(pSel->pSrc, pSel->pWhere, 0, 0) ) return;
+
+  pDup = sqlite3ExprDup(pParse->db, pExpr, 0);
+  if( pDup==0 ) return;
+  pSel = pDup->x.pSelect;
+  sqlite3ExprListDelete(pParse->db, pSel->pEList);
+  pSel->pEList = 0;
+
+  pInLhs = exprAnalyzeExistsFindEq(pSel->pSrc, pSel->pWhere, &pEq, &ppAnd);
+
+  assert( pDup->pLeft==0 );
+  pDup->op = TK_IN;
+  pDup->pLeft = pInLhs;
+  pDup->flags &= ~EP_VarSelect;
+  pRet = (pInLhs==pEq->pLeft) ? pEq->pRight : pEq->pLeft;
+  pSel->pEList = sqlite3ExprListAppend(pParse, 0, pRet);
+  pEq->pLeft = 0;
+  pEq->pRight = 0;
+  if( ppAnd ){
+    Expr *pAnd = *ppAnd;
+    Expr *pOther = (pAnd->pLeft==pEq) ? pAnd->pRight : pAnd->pLeft;
+    pAnd->pLeft = pAnd->pRight = 0;
+    sqlite3ExprDelete(pParse->db, pAnd);
+    *ppAnd = pOther;
+  }else{
+    assert( pSel->pWhere==pEq );
+    pSel->pWhere = 0;
+  }
+  sqlite3ExprDelete(pParse->db, pEq);
+
+  idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
+  if( idxNew ){
+    exprAnalyze(pSrc, pWC, idxNew);
+    markTermAsChild(pWC, idxNew, idxTerm);
+    pWC->a[idxTerm].wtFlags |= TERM_COPIED;
+  }
+}
+
 /*
 ** The input to this routine is an WhereTerm structure with only the
 ** "pExpr" field filled in.  The job of this routine is to analyze the
@@ -1418,6 +1614,10 @@ static void exprAnalyze(
   }
 #endif /* SQLITE_ENABLE_STAT4 */
 
+  if( pExpr->op==TK_EXISTS && (pExpr->flags & EP_VarSelect) ){
+    exprAnalyzeExists(pSrc, pWC, idxTerm);
+  }
+
   /* Prevent ON clause terms of a LEFT JOIN from being used to drive
   ** an index for tables to the left of the join.
   */

From 76cac6ef0663c097c9ba5195556963567cece3b5 Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Fri, 15 Jan 2021 11:39:46 +0000
Subject: [PATCH 02/13] Add simple tests (and a fix) for the change on this
 branch.

FossilOrigin-Name: 897f3f40267dc922f0fda287484435e1fd8709bade3e87c3829e2f945bb5e4aa
---
 manifest          | 16 ++++-----
 manifest.uuid     |  2 +-
 src/whereexpr.c   | 27 +++++++--------
 test/exists2.test | 87 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 107 insertions(+), 25 deletions(-)
 create mode 100644 test/exists2.test

diff --git a/manifest b/manifest
index a99b42e9cc..93a625e98a 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Allow\sthe\splanner\sto\sconvert\san\sEXISTS(SELECT...)\sexpression\sin\sa\sWHERE\sclause\sto\sthe\sequivalent\sIN(...)\sexpression\sin\ssituations\swhere\sthis\sis\spossible\sand\sadvantageous.
-D 2021-01-14T20:50:40.571
+C Add\ssimple\stests\s(and\sa\sfix)\sfor\sthe\schange\son\sthis\sbranch.
+D 2021-01-15T11:39:46.131
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 3d31871d03906312d7d71a9c0b28c97bcbaead7606dfc15f9b3d080b18702385
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c e48e3edea45b4afabbf6f6ece9647734c828a20c49a8cc780ff4d69b42f55fa4
+F src/whereexpr.c 1f4fac8ea8eac6facb9e80107c659094a56a8ad0b35108717ac99ea57bbc71bc
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -874,6 +874,7 @@ F test/exclusive.test 7ff63be7503990921838d5c9f77f6e33e68e48ed1a9d48cd28745bf650
 F test/exclusive2.test 984090e8e9d1b331d2e8111daf6e5d61dda0bef7
 F test/exec.test e949714dc127eaa5ecc7d723efec1ec27118fdd7
 F test/exists.test 79a75323c78f02bbe9c251ea502a092f9ef63dac
+F test/exists2.test 44e18a6aaadefa8e1c68a8453fb22a57a0270a673d9b256790d142ea257459e3
 F test/expr.test 26cd01e8485bc48c8aa6a1add598e9ce1e706b4eb4f3f554e0b0223022e8c2cf
 F test/expr2.test c27327ae9c017a7ff6280123f67aff496f912da74d78c888926d68b46ec75fd8
 F test/extension01.test 00d13cec817f331a687a243e0e5a2d87b0e358c9
@@ -1895,10 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 11e4eb095746602961a178044809a68a77ba7b367596997bef726e54062423d9
-R 1a9ea60bc9bb7dab69ccea9e0b8c40d8
-T *branch * exists-to-in
-T *sym-exists-to-in *
-T -sym-trunk *
+P 9f90a88221d0694951c353e58efce342eb0b868b8ca6a4469c8205e5c7855b24
+R 9984162db1d3035db01dde79c4fce484
 U dan
-Z d4d95c9878f460cd53a2ce8ada6afd2a
+Z 278fef5940bb689562d7ebf0ab17cbb2
diff --git a/manifest.uuid b/manifest.uuid
index e8520659ef..ace34aaabc 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9f90a88221d0694951c353e58efce342eb0b868b8ca6a4469c8205e5c7855b24
\ No newline at end of file
+897f3f40267dc922f0fda287484435e1fd8709bade3e87c3829e2f945bb5e4aa
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 9326a57fcb..e5e566bbfe 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1062,18 +1062,14 @@ struct ExistsToInCtx {
   Expr **ppParent;
 };
 
-static int exprExistsToInIter(
-  struct ExistsToInCtx *p, 
-  Expr *pExpr, 
-  Expr **ppExpr
-){
-  assert( ppExpr==0 || *ppExpr==pExpr );
+static int exprExistsToInIter(struct ExistsToInCtx *p, Expr **ppExpr){
+  Expr *pExpr = *ppExpr;
   switch( pExpr->op ){
     case TK_AND:
       p->ppParent = ppExpr;
-      if( exprExistsToInIter(p, pExpr->pLeft, &pExpr->pLeft) ) return 1;
+      if( exprExistsToInIter(p, &pExpr->pLeft) ) return 1;
       p->ppParent = ppExpr;
-      if( exprExistsToInIter(p, pExpr->pRight, &pExpr->pRight) ) return 1;
+      if( exprExistsToInIter(p, &pExpr->pRight) ) return 1;
       break;
     case TK_EQ: {
       int bLeft = exprUsesSrclist(p->pSrc, pExpr->pLeft, 0);
@@ -1081,9 +1077,9 @@ static int exprExistsToInIter(
       if( bLeft || bRight ){
         if( (bLeft && bRight) || p->pInLhs ) return 1;
         p->pInLhs = bLeft ? pExpr->pLeft : pExpr->pRight;
+        if( exprUsesSrclist(p->pSrc, p->pInLhs, 1) ) return 1;
         p->pEq = pExpr;
         p->ppAnd = p->ppParent;
-        if( exprUsesSrclist(p->pSrc, p->pInLhs, 1) ) return 1;
       }
       break;
     }
@@ -1098,15 +1094,14 @@ static int exprExistsToInIter(
 }
 
 static Expr *exprAnalyzeExistsFindEq(
-  SrcList *pSrc,
-  Expr *pWhere,                   /* WHERE clause to traverse */
+  Select *pSel,
   Expr **ppEq,                    /* OUT: == node from WHERE clause */
   Expr ***pppAnd                  /* OUT: Pointer to parent of ==, if any */
 ){
   struct ExistsToInCtx ctx;
   memset(&ctx, 0, sizeof(ctx));
-  ctx.pSrc = pSrc;
-  if( exprExistsToInIter(&ctx, pWhere, 0) ){
+  ctx.pSrc = pSel->pSrc;
+  if( exprExistsToInIter(&ctx, &pSel->pWhere) ){
     return 0;
   }
   if( ppEq ) *ppEq = ctx.pEq;
@@ -1165,7 +1160,7 @@ static void exprAnalyzeExists(
   if( (pSel->selFlags & SF_Aggregate) || pSel->pWin ) return;
   if( pSel->pPrior ) return;
   if( pSel->pWhere==0 ) return;
-  if( 0==exprAnalyzeExistsFindEq(pSel->pSrc, pSel->pWhere, 0, 0) ) return;
+  if( 0==exprAnalyzeExistsFindEq(pSel, 0, 0) ) return;
 
   pDup = sqlite3ExprDup(pParse->db, pExpr, 0);
   if( pDup==0 ) return;
@@ -1173,7 +1168,9 @@ static void exprAnalyzeExists(
   sqlite3ExprListDelete(pParse->db, pSel->pEList);
   pSel->pEList = 0;
 
-  pInLhs = exprAnalyzeExistsFindEq(pSel->pSrc, pSel->pWhere, &pEq, &ppAnd);
+  pInLhs = exprAnalyzeExistsFindEq(pSel, &pEq, &ppAnd);
+  assert( pInLhs && pEq );
+  assert( pEq==pSel->pWhere || ppAnd );
 
   assert( pDup->pLeft==0 );
   pDup->op = TK_IN;
diff --git a/test/exists2.test b/test/exists2.test
new file mode 100644
index 0000000000..55369f8f2f
--- /dev/null
+++ b/test/exists2.test
@@ -0,0 +1,87 @@
+# 2021 January 15
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing cases where EXISTS expressions are
+# transformed to IN() expressions by where.c
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix exists2
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b);
+  INSERT INTO t1 VALUES(1, 'one');
+  INSERT INTO t1 VALUES(2, 'two');
+  INSERT INTO t1 VALUES(3, 'three');
+  INSERT INTO t1 VALUES(4, 'four');
+  INSERT INTO t1 VALUES(5, 'five');
+  INSERT INTO t1 VALUES(6, 'six');
+  INSERT INTO t1 VALUES(7, 'seven');
+
+  CREATE TABLE t2(c INTEGER, d INTEGER);
+  INSERT INTO t2 VALUES(1, 1);
+  INSERT INTO t2 VALUES(3, 2);
+  INSERT INTO t2 VALUES(5, 3);
+  INSERT INTO t2 VALUES(7, 4);
+}
+
+proc do_execsql_eqp_test {tn sql eqp res} {
+  uplevel [list do_eqp_test $tn.1 $sql [string trim $eqp]]
+  uplevel [list do_execsql_test $tn.2 $sql $res]
+}
+
+do_execsql_eqp_test 1.1 {
+  SELECT t1.* FROM t1 WHERE EXISTS(SELECT * FROM t2 WHERE t1.a=t2.c);
+} {
+  USING INTEGER PRIMARY KEY
+} {
+  1 one 3 three 5 five 7 seven
+}
+
+do_execsql_eqp_test 1.2 {
+  SELECT t1.* FROM t1 WHERE EXISTS(SELECT * FROM t2 WHERE t2.c=t1.a);
+} {
+  SEARCH TABLE t1 USING INTEGER PRIMARY KEY
+} {
+  1 one 3 three 5 five 7 seven
+}
+
+do_execsql_eqp_test 1.3 {
+  SELECT t1.* FROM t1 WHERE EXISTS(SELECT * FROM t2 WHERE t2.c+1=t1.a);
+} {
+  SEARCH TABLE t1 USING INTEGER PRIMARY KEY
+} {
+  2 two 4 four 6 six
+}
+
+do_execsql_eqp_test 1.4 {
+  SELECT t1.* FROM t1 WHERE EXISTS(SELECT * FROM t2 WHERE t2.c+1=t1.a+1);
+} {
+  SCAN TABLE t1
+} {
+  1 one 3 three 5 five 7 seven
+}
+
+breakpoint
+do_execsql_eqp_test 1.5 {
+  SELECT t1.* FROM t1 WHERE EXISTS(
+    SELECT * FROM t2 WHERE t1.a=t2.c AND d IN (1, 2, 3)
+  );
+} {
+  SEARCH TABLE t1 USING INTEGER PRIMARY KEY
+} {
+  1 one 3 three 5 five
+}
+
+
+
+finish_test

From 10c9ef65fa7d453bfd8b1d82f434f29938d39342 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Fri, 15 Jan 2021 14:25:06 +0000
Subject: [PATCH 03/13] Small performance improvement in the EXISTS-to-IN
 translator for the common case where the EXISTS operator is not found in the
 WHERE clause.

FossilOrigin-Name: dcb7772d7695ddbc0fe89e06c07ff4a6ae4fa05de914e2ec10b5cc07a62ed49f
---
 manifest        | 12 ++++++------
 manifest.uuid   |  2 +-
 src/whereexpr.c | 12 ++++++++----
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/manifest b/manifest
index afcc0dca9c..c7f52277ae 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Merge\sthe\slatest\strunk\senhancements\sinto\sthe\sexists-to-in\sbranch.
-D 2021-01-15T14:15:31.281
+C Small\sperformance\simprovement\sin\sthe\sEXISTS-to-IN\stranslator\sfor\sthe\ncommon\scase\swhere\sthe\sEXISTS\soperator\sis\snot\sfound\sin\sthe\sWHERE\sclause.
+D 2021-01-15T14:25:06.079
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 1f4fac8ea8eac6facb9e80107c659094a56a8ad0b35108717ac99ea57bbc71bc
+F src/whereexpr.c 0ba5c743ee34255658051179441a13297dc2d6b21ef3c41120659ae3dd896ae8
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1896,7 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 897f3f40267dc922f0fda287484435e1fd8709bade3e87c3829e2f945bb5e4aa 249a71cc6822d6bdd5bb9e727aac81c6549693b418e9c0987b96850ee332c940
-R 6fb3b1c5ffde39ec234334a7c5ffcb56
+P 13c4c9088cc8a2426e30a2ad1e9b9969407249281c6ed16653d43a0e6852a2e4
+R c79f76fc898939a9f2cc931eb9a2c482
 U drh
-Z 90ae5651a54d924d6159985985e1584c
+Z e1fe560394403461c8187fdaaf345432
diff --git a/manifest.uuid b/manifest.uuid
index 88f1bf8bca..13001fa395 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-13c4c9088cc8a2426e30a2ad1e9b9969407249281c6ed16653d43a0e6852a2e4
\ No newline at end of file
+dcb7772d7695ddbc0fe89e06c07ff4a6ae4fa05de914e2ec10b5cc07a62ed49f
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index e5e566bbfe..e360001931 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1385,6 +1385,14 @@ static void exprAnalyze(
   }
 #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
 
+  else if( pExpr->op==TK_EXISTS ){
+    /* Perhaps treat an EXISTS operator as an IN operator */
+    if( (pExpr->flags & EP_VarSelect)!=0 ){
+      exprAnalyzeExists(pSrc, pWC, idxTerm);
+    }
+  }
+
+
 #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
   /* Add constraints to reduce the search space on a LIKE or GLOB
   ** operator.
@@ -1611,10 +1619,6 @@ static void exprAnalyze(
   }
 #endif /* SQLITE_ENABLE_STAT4 */
 
-  if( pExpr->op==TK_EXISTS && (pExpr->flags & EP_VarSelect) ){
-    exprAnalyzeExists(pSrc, pWC, idxTerm);
-  }
-
   /* Prevent ON clause terms of a LEFT JOIN from being used to drive
   ** an index for tables to the left of the join.
   */

From 19ef211d85972c998ce8baa834efe0797f1ab492 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Fri, 15 Jan 2021 15:17:14 +0000
Subject: [PATCH 04/13] Add a new optimizer disabling bit to close off the
 exists-to-in optimization, for testing purposes.

FossilOrigin-Name: a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87
---
 manifest        | 14 +++++++-------
 manifest.uuid   |  2 +-
 src/sqliteInt.h |  1 +
 src/whereexpr.c |  4 +++-
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/manifest b/manifest
index c7f52277ae..0e289c8966 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Small\sperformance\simprovement\sin\sthe\sEXISTS-to-IN\stranslator\sfor\sthe\ncommon\scase\swhere\sthe\sEXISTS\soperator\sis\snot\sfound\sin\sthe\sWHERE\sclause.
-D 2021-01-15T14:25:06.079
+C Add\sa\snew\soptimizer\sdisabling\sbit\sto\sclose\soff\sthe\sexists-to-in\soptimization,\nfor\stesting\spurposes.
+D 2021-01-15T15:17:14.152
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -545,7 +545,7 @@ F src/shell.c.in 9ebc74e4f05cfbd0f4a36060fdaeff1da4e9af4458358722bc08c5a1ab9a087
 F src/sqlite.h.in 0af968a1fa3c717261e1df0ed105fa7bddb4d82de7e0adb3eab49e6aa81b4de7
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 61b38c073d5e1e96a3d45271b257aef27d0d13da2bea5347692ae579475cd95e
-F src/sqliteInt.h 6aad58a5ae1374e18ea53d0c3ea71f047b67313426767783bd7fa14ee786725a
+F src/sqliteInt.h d921214bba203960de10ea7a9183735ec362a5def5910d468282a8f82e8b4c26
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 4b8bc2a6905163a38b739854a35b826c737333fab5b1f8e03fa7eb9a4799c4c1
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 0ba5c743ee34255658051179441a13297dc2d6b21ef3c41120659ae3dd896ae8
+F src/whereexpr.c 2d42217961cf8da8280779df88bcfb7cb3ee719369cafb44ac2b376fdecf9db7
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1896,7 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 13c4c9088cc8a2426e30a2ad1e9b9969407249281c6ed16653d43a0e6852a2e4
-R c79f76fc898939a9f2cc931eb9a2c482
+P dcb7772d7695ddbc0fe89e06c07ff4a6ae4fa05de914e2ec10b5cc07a62ed49f
+R 6fb63e2f60db07c2af9d4dfa7cc52f88
 U drh
-Z e1fe560394403461c8187fdaaf345432
+Z 5ba57a27c0ec24c2bc90f07584644072
diff --git a/manifest.uuid b/manifest.uuid
index 13001fa395..1f56d238fa 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-dcb7772d7695ddbc0fe89e06c07ff4a6ae4fa05de914e2ec10b5cc07a62ed49f
\ No newline at end of file
+a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87
\ No newline at end of file
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 0581e907da..e1e0707bf3 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1721,6 +1721,7 @@ struct sqlite3 {
 #define SQLITE_SkipScan       0x00004000 /* Skip-scans */
 #define SQLITE_PropagateConst 0x00008000 /* The constant propagation opt */
 #define SQLITE_MinMaxOpt      0x00010000 /* The min/max optimization */
+#define SQLITE_ExistsToIN     0x00020000 /* The EXISTS-to-IN optimization */
 #define SQLITE_AllOpts        0xffffffff /* All optimizations */
 
 /*
diff --git a/src/whereexpr.c b/src/whereexpr.c
index e360001931..4de5af1730 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1387,7 +1387,9 @@ static void exprAnalyze(
 
   else if( pExpr->op==TK_EXISTS ){
     /* Perhaps treat an EXISTS operator as an IN operator */
-    if( (pExpr->flags & EP_VarSelect)!=0 ){
+    if( (pExpr->flags & EP_VarSelect)!=0
+     && OptimizationEnabled(db, SQLITE_ExistsToIN)
+    ){
       exprAnalyzeExists(pSrc, pWC, idxTerm);
     }
   }

From 9d326d67937b23217718cc64e67d214351691a2a Mon Sep 17 00:00:00 2001
From: drh <>
Date: Fri, 15 Jan 2021 15:21:27 +0000
Subject: [PATCH 05/13] Fix a potential NULL pointer dereference following OOM.

FossilOrigin-Name: 8ce3cb90965771530c0021173d98720fc4c76bb99e69f7a879f80471dea0aace
---
 manifest        | 12 ++++++------
 manifest.uuid   |  2 +-
 src/whereexpr.c | 14 +++++++++-----
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/manifest b/manifest
index 0e289c8966..235abe4634 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sa\snew\soptimizer\sdisabling\sbit\sto\sclose\soff\sthe\sexists-to-in\soptimization,\nfor\stesting\spurposes.
-D 2021-01-15T15:17:14.152
+C Fix\sa\spotential\sNULL\spointer\sdereference\sfollowing\sOOM.
+D 2021-01-15T15:21:27.437
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 2d42217961cf8da8280779df88bcfb7cb3ee719369cafb44ac2b376fdecf9db7
+F src/whereexpr.c 8ea4f6cd1332fdfbfbe832dc8a9f5194990684870931e7a07c2cafbc544588e7
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1896,7 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P dcb7772d7695ddbc0fe89e06c07ff4a6ae4fa05de914e2ec10b5cc07a62ed49f
-R 6fb63e2f60db07c2af9d4dfa7cc52f88
+P a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87
+R 31b39e7a643244cb65bba0cd39985e5a
 U drh
-Z 5ba57a27c0ec24c2bc90f07584644072
+Z 96ac907b935dc11fb79e0a38f40aef27
diff --git a/manifest.uuid b/manifest.uuid
index 1f56d238fa..b72b9116a2 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87
\ No newline at end of file
+8ce3cb90965771530c0021173d98720fc4c76bb99e69f7a879f80471dea0aace
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 4de5af1730..0359babc50 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1153,6 +1153,7 @@ static void exprAnalyzeExists(
   Expr *pInLhs = 0;
   Expr **ppAnd = 0;
   int idxNew;
+  sqlite3 *db = pParse->db;
 
   assert( pExpr->op==TK_EXISTS );
   assert( (pExpr->flags & EP_VarSelect) && (pExpr->flags & EP_xIsSelect) );
@@ -1162,10 +1163,13 @@ static void exprAnalyzeExists(
   if( pSel->pWhere==0 ) return;
   if( 0==exprAnalyzeExistsFindEq(pSel, 0, 0) ) return;
 
-  pDup = sqlite3ExprDup(pParse->db, pExpr, 0);
-  if( pDup==0 ) return;
+  pDup = sqlite3ExprDup(db, pExpr, 0);
+  if( db->mallocFailed ){
+    sqlite3ExprDelete(db, pDup);
+    return;
+  }
   pSel = pDup->x.pSelect;
-  sqlite3ExprListDelete(pParse->db, pSel->pEList);
+  sqlite3ExprListDelete(db, pSel->pEList);
   pSel->pEList = 0;
 
   pInLhs = exprAnalyzeExistsFindEq(pSel, &pEq, &ppAnd);
@@ -1184,13 +1188,13 @@ static void exprAnalyzeExists(
     Expr *pAnd = *ppAnd;
     Expr *pOther = (pAnd->pLeft==pEq) ? pAnd->pRight : pAnd->pLeft;
     pAnd->pLeft = pAnd->pRight = 0;
-    sqlite3ExprDelete(pParse->db, pAnd);
+    sqlite3ExprDelete(db, pAnd);
     *ppAnd = pOther;
   }else{
     assert( pSel->pWhere==pEq );
     pSel->pWhere = 0;
   }
-  sqlite3ExprDelete(pParse->db, pEq);
+  sqlite3ExprDelete(db, pEq);
 
   idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
   if( idxNew ){

From e8f7fcf6f4a3655334251ad638db47bcdde37a9c Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Fri, 15 Jan 2021 15:32:09 +0000
Subject: [PATCH 06/13] Ensure the EXISTS->IN transformation preserves the
 collation sequence of the comparison operation.

FossilOrigin-Name: a373baae12c914e48fd84de77998e301fdd3da43b06b9d64ac24a14418ed48cd
---
 manifest          | 16 +++++-----
 manifest.uuid     |  2 +-
 src/whereexpr.c   |  8 ++++-
 test/exists2.test | 78 ++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 93 insertions(+), 11 deletions(-)

diff --git a/manifest b/manifest
index 235abe4634..1523531c03 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\spotential\sNULL\spointer\sdereference\sfollowing\sOOM.
-D 2021-01-15T15:21:27.437
+C Ensure\sthe\sEXISTS->IN\stransformation\spreserves\sthe\scollation\ssequence\sof\sthe\scomparison\soperation.
+D 2021-01-15T15:32:09.587
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 8ea4f6cd1332fdfbfbe832dc8a9f5194990684870931e7a07c2cafbc544588e7
+F src/whereexpr.c d63dcb44253f7ad67449759bca6da63cac1c352aba7bea46ba3210154ad21e22
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -874,7 +874,7 @@ F test/exclusive.test 7ff63be7503990921838d5c9f77f6e33e68e48ed1a9d48cd28745bf650
 F test/exclusive2.test 984090e8e9d1b331d2e8111daf6e5d61dda0bef7
 F test/exec.test e949714dc127eaa5ecc7d723efec1ec27118fdd7
 F test/exists.test 79a75323c78f02bbe9c251ea502a092f9ef63dac
-F test/exists2.test 44e18a6aaadefa8e1c68a8453fb22a57a0270a673d9b256790d142ea257459e3
+F test/exists2.test 1022fe1c85ee162ae55efda6c00497b29d1f61ecb21e7d5f1c014eb46245c70a
 F test/expr.test 26cd01e8485bc48c8aa6a1add598e9ce1e706b4eb4f3f554e0b0223022e8c2cf
 F test/expr2.test c27327ae9c017a7ff6280123f67aff496f912da74d78c888926d68b46ec75fd8
 F test/extension01.test 00d13cec817f331a687a243e0e5a2d87b0e358c9
@@ -1896,7 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P a80c9a076d31729282004ca372913c9fdbfb6e74711fbb8c5dc12ee0ecba2b87
-R 31b39e7a643244cb65bba0cd39985e5a
-U drh
-Z 96ac907b935dc11fb79e0a38f40aef27
+P 8ce3cb90965771530c0021173d98720fc4c76bb99e69f7a879f80471dea0aace
+R bc5d3e0052171a4a3fcfe5fb2a3891b3
+U dan
+Z 4e48cccd8bd31a2f422fbd932b326f93
diff --git a/manifest.uuid b/manifest.uuid
index b72b9116a2..58184acaa4 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-8ce3cb90965771530c0021173d98720fc4c76bb99e69f7a879f80471dea0aace
\ No newline at end of file
+a373baae12c914e48fd84de77998e301fdd3da43b06b9d64ac24a14418ed48cd
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 0359babc50..82a9759f39 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1175,12 +1175,18 @@ static void exprAnalyzeExists(
   pInLhs = exprAnalyzeExistsFindEq(pSel, &pEq, &ppAnd);
   assert( pInLhs && pEq );
   assert( pEq==pSel->pWhere || ppAnd );
+  if( pInLhs==pEq->pLeft ){
+    pRet = pEq->pRight;
+  }else{
+    CollSeq *p = sqlite3ExprCompareCollSeq(pParse, pEq);
+    pInLhs = sqlite3ExprAddCollateString(pParse, pInLhs, p?p->zName:"BINARY");
+    pRet = pEq->pLeft;
+  }
 
   assert( pDup->pLeft==0 );
   pDup->op = TK_IN;
   pDup->pLeft = pInLhs;
   pDup->flags &= ~EP_VarSelect;
-  pRet = (pInLhs==pEq->pLeft) ? pEq->pRight : pEq->pLeft;
   pSel->pEList = sqlite3ExprListAppend(pParse, 0, pRet);
   pEq->pLeft = 0;
   pEq->pRight = 0;
diff --git a/test/exists2.test b/test/exists2.test
index 55369f8f2f..3472751a21 100644
--- a/test/exists2.test
+++ b/test/exists2.test
@@ -71,7 +71,6 @@ do_execsql_eqp_test 1.4 {
   1 one 3 three 5 five 7 seven
 }
 
-breakpoint
 do_execsql_eqp_test 1.5 {
   SELECT t1.* FROM t1 WHERE EXISTS(
     SELECT * FROM t2 WHERE t1.a=t2.c AND d IN (1, 2, 3)
@@ -82,6 +81,83 @@ do_execsql_eqp_test 1.5 {
   1 one 3 three 5 five
 }
 
+do_execsql_eqp_test 1.6 {
+  SELECT t1.* FROM t1 WHERE EXISTS(
+    SELECT * FROM t2 WHERE d IN (1, 2, 3)AND t1.a=t2.c 
+  );
+} {
+  SEARCH TABLE t1 USING INTEGER PRIMARY KEY
+} {
+  1 one 3 three 5 five
+}
+
+do_execsql_eqp_test 1.7 {
+  SELECT t1.* FROM t1 WHERE EXISTS(
+    SELECT * FROM t2 WHERE d IN (1, 2, 3)AND t1.a=t2.c 
+  );
+} {
+  SEARCH TABLE t1 USING INTEGER PRIMARY KEY
+} {
+  1 one 3 three 5 five
+}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+do_execsql_test 2.0 {
+  CREATE TABLE t3(a TEXT PRIMARY KEY, b TEXT) WITHOUT ROWID;
+  CREATE TABLE t4(c TEXT COLLATE nocase);
+
+  INSERT INTO t3 VALUES('one', 'i');
+  INSERT INTO t3 VALUES('two', 'ii');
+  INSERT INTO t3 VALUES('three', 'iii');
+  INSERT INTO t3 VALUES('four', 'iv');
+  INSERT INTO t3 VALUES('five', 'v');
+
+  INSERT INTO t4 VALUES('FIVE'), ('four'), ('TWO'), ('one');
+}
+
+do_execsql_test 2.1 { SELECT a FROM t3, t4 WHERE a=c } {four one}
+do_execsql_test 2.2 { SELECT a FROM t3, t4 WHERE c=a } {five four one two}
+
+do_execsql_eqp_test 2.3 {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE a=c)
+} {
+  SEARCH TABLE t3 USING PRIMARY KEY
+} {
+  four one
+}
+
+do_execsql_eqp_test 2.4 {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE c=a)
+} {
+  SCAN TABLE t3
+} {
+  five four one two
+}
+
+do_execsql_test 2.5 {
+  CREATE INDEX t3anc ON t3(a COLLATE nocase);
+}
+
+do_execsql_eqp_test 2.6 {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE c=a)
+} {
+  SEARCH TABLE t3 USING COVERING INDEX t3anc
+} {
+  five four one two
+}
+
+do_execsql_eqp_test 2.7 {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE a=c)
+} {
+  SEARCH TABLE t3 USING PRIMARY KEY
+} {
+  four one
+}
+
+
 
 
 finish_test
+

From a828d565b6b1b0fa6f97175f3d7934100a69b505 Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Fri, 15 Jan 2021 16:37:32 +0000
Subject: [PATCH 07/13] Update header comments for routines added by this
 branch.

FossilOrigin-Name: 950030d679933f9ccd2b86ee650a4a78d338278a3629f0d289cca720a43e686b
---
 manifest        | 12 ++++++------
 manifest.uuid   |  2 +-
 src/whereexpr.c | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/manifest b/manifest
index 1523531c03..7005bdf9f6 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Ensure\sthe\sEXISTS->IN\stransformation\spreserves\sthe\scollation\ssequence\sof\sthe\scomparison\soperation.
-D 2021-01-15T15:32:09.587
+C Update\sheader\scomments\sfor\sroutines\sadded\sby\sthis\sbranch.
+D 2021-01-15T16:37:32.495
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c d63dcb44253f7ad67449759bca6da63cac1c352aba7bea46ba3210154ad21e22
+F src/whereexpr.c 0462a66ccabeea05c2d41a1e650a9c4db5bc696b9a3b42b48a43a89a2ba81474
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1896,7 +1896,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 8ce3cb90965771530c0021173d98720fc4c76bb99e69f7a879f80471dea0aace
-R bc5d3e0052171a4a3fcfe5fb2a3891b3
+P a373baae12c914e48fd84de77998e301fdd3da43b06b9d64ac24a14418ed48cd
+R e59675eaf8d9cef929f4570c41e8d7b0
 U dan
-Z 4e48cccd8bd31a2f422fbd932b326f93
+Z 99df7f39e80917b2e7ef225da7aeef0d
diff --git a/manifest.uuid b/manifest.uuid
index 58184acaa4..a3d3997a3a 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-a373baae12c914e48fd84de77998e301fdd3da43b06b9d64ac24a14418ed48cd
\ No newline at end of file
+950030d679933f9ccd2b86ee650a4a78d338278a3629f0d289cca720a43e686b
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 82a9759f39..cdaaa7e894 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1054,6 +1054,10 @@ static int exprUsesSrclist(SrcList *pSrc, Expr *pExpr, int bUses){
   return (sqlite3WalkExpr(&sWalker, pExpr)==WRC_Abort);
 }
 
+/*
+** Context object used by exprExistsToInIter() as it iterates through an
+** expression tree.
+*/
 struct ExistsToInCtx {
   SrcList *pSrc;
   Expr *pInLhs;
@@ -1062,6 +1066,15 @@ struct ExistsToInCtx {
   Expr **ppParent;
 };
 
+/*
+** Iterate through all AND connected nodes in the expression tree
+** headed by (*ppExpr), populating the structure passed as the first
+** argument with the values required by exprAnalyzeExistsFindEq().
+**
+** This function returns non-zero if the expression tree does not meet
+** the two conditions described by the header comment for
+** exprAnalyzeExistsFindEq(), or zero if it does.
+*/
 static int exprExistsToInIter(struct ExistsToInCtx *p, Expr **ppExpr){
   Expr *pExpr = *ppExpr;
   switch( pExpr->op ){
@@ -1093,6 +1106,30 @@ static int exprExistsToInIter(struct ExistsToInCtx *p, Expr **ppExpr){
   return 0;
 }
 
+/*
+** This function is by exprAnalyzeExists() when creating virtual IN(...)
+** terms equivalent to user-supplied EXIST(...) clauses. It splits the WHERE
+** clause of the Select object passed as the first argument into one or more
+** expressions joined by AND operators, and then tests if the following are
+** true:
+**
+**   1. Exactly one of the AND separated terms refers to the outer
+**      query, and it is an == (TK_EQ) expression.
+**
+**   2. Only one side of the == expression refers to the outer query, and 
+**      it does not refer to any columns from the inner query.
+**
+** If both these conditions are true, then a pointer to the side of the ==
+** expression that refers to the outer query is returned. The caller will
+** use this expression as the LHS of the IN(...) virtual term. Or, if one
+** or both of the above conditions are not true, NULL is returned.
+**
+** If non-NULL is returned and ppEq is non-NULL, *ppEq is set to point
+** to the == expression node before returning. If pppAnd is non-NULL and
+** the == node is not the root of the WHERE clause, then *pppAnd is set
+** to point to the pointer to the AND node that is the parent of the ==
+** node within the WHERE expression tree.
+*/
 static Expr *exprAnalyzeExistsFindEq(
   Select *pSel,
   Expr **ppEq,                    /* OUT: == node from WHERE clause */

From f7588d4072453c050169f549ce06ac3cc6b259ff Mon Sep 17 00:00:00 2001
From: dan <Dan Kennedy>
Date: Fri, 15 Jan 2021 17:51:56 +0000
Subject: [PATCH 08/13] Add OOM injection tests for new code on this branch.

FossilOrigin-Name: 9a181dbaedcc2117e670e679ca94ed6d1fabd90c835671dee36424dd0646c4e5
---
 manifest              | 11 ++++-----
 manifest.uuid         |  2 +-
 test/existsfault.test | 52 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 6 deletions(-)
 create mode 100644 test/existsfault.test

diff --git a/manifest b/manifest
index 7005bdf9f6..a50135c18f 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Update\sheader\scomments\sfor\sroutines\sadded\sby\sthis\sbranch.
-D 2021-01-15T16:37:32.495
+C Add\sOOM\sinjection\stests\sfor\snew\scode\son\sthis\sbranch.
+D 2021-01-15T17:51:56.060
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -875,6 +875,7 @@ F test/exclusive2.test 984090e8e9d1b331d2e8111daf6e5d61dda0bef7
 F test/exec.test e949714dc127eaa5ecc7d723efec1ec27118fdd7
 F test/exists.test 79a75323c78f02bbe9c251ea502a092f9ef63dac
 F test/exists2.test 1022fe1c85ee162ae55efda6c00497b29d1f61ecb21e7d5f1c014eb46245c70a
+F test/existsfault.test 74f7edc713f5a335e7ff47adf503067bf05c6f8630f88b2a19c24f0fa5486ab8
 F test/expr.test 26cd01e8485bc48c8aa6a1add598e9ce1e706b4eb4f3f554e0b0223022e8c2cf
 F test/expr2.test c27327ae9c017a7ff6280123f67aff496f912da74d78c888926d68b46ec75fd8
 F test/extension01.test 00d13cec817f331a687a243e0e5a2d87b0e358c9
@@ -1896,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P a373baae12c914e48fd84de77998e301fdd3da43b06b9d64ac24a14418ed48cd
-R e59675eaf8d9cef929f4570c41e8d7b0
+P 950030d679933f9ccd2b86ee650a4a78d338278a3629f0d289cca720a43e686b
+R 9a769128390cc86c331540163e8fa29c
 U dan
-Z 99df7f39e80917b2e7ef225da7aeef0d
+Z a3f9abfbc145e44a2a1bba02d43a960d
diff --git a/manifest.uuid b/manifest.uuid
index a3d3997a3a..7877c79580 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-950030d679933f9ccd2b86ee650a4a78d338278a3629f0d289cca720a43e686b
\ No newline at end of file
+9a181dbaedcc2117e670e679ca94ed6d1fabd90c835671dee36424dd0646c4e5
\ No newline at end of file
diff --git a/test/existsfault.test b/test/existsfault.test
new file mode 100644
index 0000000000..24e44a7b58
--- /dev/null
+++ b/test/existsfault.test
@@ -0,0 +1,52 @@
+# 2021 January 15
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing cases where EXISTS expressions are
+# transformed to IN() expressions by where.c
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix existsfault
+
+do_execsql_test 1 {
+  CREATE TABLE t1(a PRIMARY KEY, b);
+  INSERT INTO t1 VALUES(1, 'one');
+  INSERT INTO t1 VALUES(2, 'two');
+  INSERT INTO t1 VALUES(3, 'three');
+  INSERT INTO t1 VALUES(4, 'four');
+  INSERT INTO t1 VALUES(5, 'five');
+  INSERT INTO t1 VALUES(6, 'six');
+  INSERT INTO t1 VALUES(7, 'seven');
+
+  CREATE TABLE t2(c INTEGER, d INTEGER);
+  INSERT INTO t2 VALUES(1, 1);
+  INSERT INTO t2 VALUES(3, 2);
+  INSERT INTO t2 VALUES(5, 3);
+  INSERT INTO t2 VALUES(7, 4);
+}
+faultsim_save_and_close
+
+do_faultsim_test 1 -prep {
+  faultsim_restore_and_reopen
+} -body {
+  execsql {
+    SELECT t1.* FROM t1 WHERE EXISTS(
+        SELECT * FROM t2 WHERE t2.c=t1.a AND d IN (1, 2, 3)
+    )
+  }
+} -test {
+  faultsim_test_result {0 {1 one 3 three 5 five}}
+}
+
+
+finish_test
+

From 2a3be742caf8c35330038ce839f9a735e847045e Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 16 Jan 2021 18:22:10 +0000
Subject: [PATCH 09/13] Add debugging output about the EXISTS-to-IN
 optimization when the ".wheretrace" flag has the 0x20 bit set.

FossilOrigin-Name: 0dad5ce34ad8a59200b013453c9334f8898e07f2c0107c8c734ecc34b67de572
---
 manifest        | 14 +++++++-------
 manifest.uuid   |  2 +-
 src/whereexpr.c | 10 +++++++++-
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/manifest b/manifest
index a50135c18f..f5d05c712c 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sOOM\sinjection\stests\sfor\snew\scode\son\sthis\sbranch.
-D 2021-01-15T17:51:56.060
+C Add\sdebugging\soutput\sabout\sthe\sEXISTS-to-IN\soptimization\swhen\nthe\s".wheretrace"\sflag\shas\sthe\s0x20\sbit\sset.
+D 2021-01-16T18:22:10.163
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 0462a66ccabeea05c2d41a1e650a9c4db5bc696b9a3b42b48a43a89a2ba81474
+F src/whereexpr.c 10ed78eb09474c4f4d2ad61c3047900897d48ce969f2fa7ef48ffd28b6d934a6
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1897,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 950030d679933f9ccd2b86ee650a4a78d338278a3629f0d289cca720a43e686b
-R 9a769128390cc86c331540163e8fa29c
-U dan
-Z a3f9abfbc145e44a2a1bba02d43a960d
+P 9a181dbaedcc2117e670e679ca94ed6d1fabd90c835671dee36424dd0646c4e5
+R 37544a92998410ad6bf700343ed335b0
+U drh
+Z b455d8286b10f237c30679d2b4a9d690
diff --git a/manifest.uuid b/manifest.uuid
index 7877c79580..c0bab29af4 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9a181dbaedcc2117e670e679ca94ed6d1fabd90c835671dee36424dd0646c4e5
\ No newline at end of file
+0dad5ce34ad8a59200b013453c9334f8898e07f2c0107c8c734ecc34b67de572
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index cdaaa7e894..1772aa7486 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1107,7 +1107,7 @@ static int exprExistsToInIter(struct ExistsToInCtx *p, Expr **ppExpr){
 }
 
 /*
-** This function is by exprAnalyzeExists() when creating virtual IN(...)
+** This function is used by exprAnalyzeExists() when creating virtual IN(...)
 ** terms equivalent to user-supplied EXIST(...) clauses. It splits the WHERE
 ** clause of the Select object passed as the first argument into one or more
 ** expressions joined by AND operators, and then tests if the following are
@@ -1239,6 +1239,14 @@ static void exprAnalyzeExists(
   }
   sqlite3ExprDelete(db, pEq);
 
+#ifdef WHERETRACE_ENABLED  /* 0x20 */
+  if( sqlite3WhereTrace & 0x20 ){
+    sqlite3DebugPrintf("Convert EXISTS:\n");
+    sqlite3TreeViewExpr(0, pExpr, 0);
+    sqlite3DebugPrintf("into IN:\n");
+    sqlite3TreeViewExpr(0, pDup, 0);
+  }
+#endif
   idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
   if( idxNew ){
     exprAnalyze(pSrc, pWC, idxNew);

From 4be8bdccd453440e653f04bb6da4dcecf4bdfa68 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 16 Jan 2021 18:55:10 +0000
Subject: [PATCH 10/13] Give the EXISTS-to-IN optimization the ability to
 handle some cases that involve vector comparisons, instead of throwing a
 mysterious error in those cases.

FossilOrigin-Name: 87e78a19bb3ae1caf57aeeae53a5ab4efdccb57265f25d5c19b62eae53747aff
---
 manifest          | 14 +++++++-------
 manifest.uuid     |  2 +-
 src/whereexpr.c   | 14 +++++++++++---
 test/exists2.test | 19 ++++++++++++++++++-
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/manifest b/manifest
index f5d05c712c..995f5e28d2 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sdebugging\soutput\sabout\sthe\sEXISTS-to-IN\soptimization\swhen\nthe\s".wheretrace"\sflag\shas\sthe\s0x20\sbit\sset.
-D 2021-01-16T18:22:10.163
+C Give\sthe\sEXISTS-to-IN\soptimization\sthe\sability\sto\shandle\ssome\scases\sthat\ninvolve\svector\scomparisons,\sinstead\sof\sthrowing\sa\smysterious\serror\sin\sthose\ncases.
+D 2021-01-16T18:55:10.186
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 10ed78eb09474c4f4d2ad61c3047900897d48ce969f2fa7ef48ffd28b6d934a6
+F src/whereexpr.c 0a3fd3667cb78d5ced831d103a9769e9429b69cc06336a557f7436a36298a08d
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -874,7 +874,7 @@ F test/exclusive.test 7ff63be7503990921838d5c9f77f6e33e68e48ed1a9d48cd28745bf650
 F test/exclusive2.test 984090e8e9d1b331d2e8111daf6e5d61dda0bef7
 F test/exec.test e949714dc127eaa5ecc7d723efec1ec27118fdd7
 F test/exists.test 79a75323c78f02bbe9c251ea502a092f9ef63dac
-F test/exists2.test 1022fe1c85ee162ae55efda6c00497b29d1f61ecb21e7d5f1c014eb46245c70a
+F test/exists2.test 3e6741849880410a438e1e016878aee518e82fc14c9df7bb8b975414e822960a
 F test/existsfault.test 74f7edc713f5a335e7ff47adf503067bf05c6f8630f88b2a19c24f0fa5486ab8
 F test/expr.test 26cd01e8485bc48c8aa6a1add598e9ce1e706b4eb4f3f554e0b0223022e8c2cf
 F test/expr2.test c27327ae9c017a7ff6280123f67aff496f912da74d78c888926d68b46ec75fd8
@@ -1897,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9a181dbaedcc2117e670e679ca94ed6d1fabd90c835671dee36424dd0646c4e5
-R 37544a92998410ad6bf700343ed335b0
+P 0dad5ce34ad8a59200b013453c9334f8898e07f2c0107c8c734ecc34b67de572
+R dac9991b639e128a44072e06099f9d5a
 U drh
-Z b455d8286b10f237c30679d2b4a9d690
+Z 4c2faa19ecfc2a7e1d7bc30b27d619e2
diff --git a/manifest.uuid b/manifest.uuid
index c0bab29af4..b027e9f246 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-0dad5ce34ad8a59200b013453c9334f8898e07f2c0107c8c734ecc34b67de572
\ No newline at end of file
+87e78a19bb3ae1caf57aeeae53a5ab4efdccb57265f25d5c19b62eae53747aff
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 1772aa7486..e3c02deacd 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1215,16 +1215,24 @@ static void exprAnalyzeExists(
   if( pInLhs==pEq->pLeft ){
     pRet = pEq->pRight;
   }else{
-    CollSeq *p = sqlite3ExprCompareCollSeq(pParse, pEq);
-    pInLhs = sqlite3ExprAddCollateString(pParse, pInLhs, p?p->zName:"BINARY");
     pRet = pEq->pLeft;
+    if( pRet->op!=TK_VECTOR ){
+      CollSeq *p = sqlite3ExprCompareCollSeq(pParse, pEq);
+      pInLhs = sqlite3ExprAddCollateString(pParse, pInLhs, p?p->zName:"BINARY");
+    }
   }
 
   assert( pDup->pLeft==0 );
   pDup->op = TK_IN;
   pDup->pLeft = pInLhs;
   pDup->flags &= ~EP_VarSelect;
-  pSel->pEList = sqlite3ExprListAppend(pParse, 0, pRet);
+  if( pRet->op==TK_VECTOR ){
+    pSel->pEList = pRet->x.pList;
+    pRet->x.pList = 0;
+    sqlite3ExprDelete(db, pRet);
+  }else{
+    pSel->pEList = sqlite3ExprListAppend(pParse, 0, pRet);
+  }
   pEq->pLeft = 0;
   pEq->pRight = 0;
   if( ppAnd ){
diff --git a/test/exists2.test b/test/exists2.test
index 3472751a21..a28e5daaef 100644
--- a/test/exists2.test
+++ b/test/exists2.test
@@ -156,8 +156,25 @@ do_execsql_eqp_test 2.7 {
   four one
 }
 
+# EXISTS clauses using vector expressions in the WHERE clause.
+#
+reset_db
+do_execsql_test 3.0 {
+  CREATE TABLE t1(a,b);
+  INSERT INTO t1(a,b) VALUES(1,111),(2,222),(8,888);
+  CREATE TABLE t2(x INTEGER PRIMARY KEY, y);
+  INSERT INTO t2(x,y) VALUES(2,222),(3,333),(7,333);
+  SELECT y FROM t2 WHERE EXISTS(SELECT 1 FROM t1 WHERE (x,y)=(a,b));
+} {222}
+do_execsql_test 3.1 {
+  SELECT y FROM t2 WHERE EXISTS(SELECT 1 FROM t1 WHERE (a,b)=(x,y));
+} {222}
+do_execsql_test 3.2 {
+  SELECT y FROM t2 WHERE EXISTS(SELECT 1 FROM t1 WHERE (x,b)=(a,y));
+} {222}
+
+
 
 
 
 finish_test
-

From 9ffa258a01ff64cce868f452164a001e702561b5 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sat, 16 Jan 2021 20:22:11 +0000
Subject: [PATCH 11/13] Improved handling of vector equalities in the
 EXISTS-to-IN translator.

FossilOrigin-Name: ef49ee4a3766146963bfb6b013472f9836afb9c5b0d21a8533871cf961139e38
---
 manifest          | 16 ++++++++--------
 manifest.uuid     |  2 +-
 src/expr.c        | 13 ++++++++++++-
 src/whereexpr.c   |  6 ++----
 test/exists2.test | 26 +++++++++++++++++---------
 5 files changed, 40 insertions(+), 23 deletions(-)

diff --git a/manifest b/manifest
index 995f5e28d2..2755d47c82 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Give\sthe\sEXISTS-to-IN\soptimization\sthe\sability\sto\shandle\ssome\scases\sthat\ninvolve\svector\scomparisons,\sinstead\sof\sthrowing\sa\smysterious\serror\sin\sthose\ncases.
-D 2021-01-16T18:55:10.186
+C Improved\shandling\sof\svector\sequalities\sin\sthe\sEXISTS-to-IN\stranslator.
+D 2021-01-16T20:22:11.928
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -492,7 +492,7 @@ F src/date.c dace306a10d9b02ee553d454c8e1cf8d3c9b932e137738a6b15b90253a9bfc10
 F src/dbpage.c 8a01e865bf8bc6d7b1844b4314443a6436c07c3efe1d488ed89e81719047833a
 F src/dbstat.c 3aa79fc3aed7ce906e4ea6c10e85d657299e304f6049861fe300053ac57de36c
 F src/delete.c 927cf8f900583e79aca8f1a321979e0a8f053babd9a690b44b38f79de2cc09fe
-F src/expr.c 0d196ed5a2ebf96be7e8df88add4fabfad0dce16c0fed81a4b8f6a26e259797f
+F src/expr.c 47c85263e6d179424e6b09e2c79db5704ab5b8cbc2fae2ee3285faa2566f2e74
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c 83372403298e6a7dd989a47aaacdbaa5b4307b5199dbd56e07d4896066b3de72
 F src/func.c 251b5953cecd0ce3e282213c5e623134415793d3569d7804d13460559d7e45ff
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 0a3fd3667cb78d5ced831d103a9769e9429b69cc06336a557f7436a36298a08d
+F src/whereexpr.c 9fdbed19035077e41ca993ab469114e9b6b0746c18ea4e7675a850713b35fc72
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -874,7 +874,7 @@ F test/exclusive.test 7ff63be7503990921838d5c9f77f6e33e68e48ed1a9d48cd28745bf650
 F test/exclusive2.test 984090e8e9d1b331d2e8111daf6e5d61dda0bef7
 F test/exec.test e949714dc127eaa5ecc7d723efec1ec27118fdd7
 F test/exists.test 79a75323c78f02bbe9c251ea502a092f9ef63dac
-F test/exists2.test 3e6741849880410a438e1e016878aee518e82fc14c9df7bb8b975414e822960a
+F test/exists2.test 3e5726d6a67ebd4bd3466db58be424c09156c1f276c7594abb260cbf6ad494d3
 F test/existsfault.test 74f7edc713f5a335e7ff47adf503067bf05c6f8630f88b2a19c24f0fa5486ab8
 F test/expr.test 26cd01e8485bc48c8aa6a1add598e9ce1e706b4eb4f3f554e0b0223022e8c2cf
 F test/expr2.test c27327ae9c017a7ff6280123f67aff496f912da74d78c888926d68b46ec75fd8
@@ -1897,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0dad5ce34ad8a59200b013453c9334f8898e07f2c0107c8c734ecc34b67de572
-R dac9991b639e128a44072e06099f9d5a
+P 87e78a19bb3ae1caf57aeeae53a5ab4efdccb57265f25d5c19b62eae53747aff
+R 9040bb485a8bcb3beab221382ed76aaa
 U drh
-Z 4c2faa19ecfc2a7e1d7bc30b27d619e2
+Z 15d0a474b0220437a1e81a3ea0fc01b3
diff --git a/manifest.uuid b/manifest.uuid
index b027e9f246..773b82c6ef 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-87e78a19bb3ae1caf57aeeae53a5ab4efdccb57265f25d5c19b62eae53747aff
\ No newline at end of file
+ef49ee4a3766146963bfb6b013472f9836afb9c5b0d21a8533871cf961139e38
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index 685f041752..f225b59bce 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -95,7 +95,18 @@ Expr *sqlite3ExprAddCollateToken(
   const Token *pCollName,  /* Name of collating sequence */
   int dequote              /* True to dequote pCollName */
 ){
-  if( pCollName->n>0 ){
+  assert( pExpr!=0 || pParse->db->mallocFailed );
+  if( pExpr==0 ) return 0;
+  if( pExpr->op==TK_VECTOR ){
+    ExprList *pList = pExpr->x.pList;
+    if( ALWAYS(pList!=0) ){
+      int i;
+      for(i=0; i<pList->nExpr; i++){
+        pList->a[i].pExpr = sqlite3ExprAddCollateToken(pParse,pList->a[i].pExpr,
+                                                       pCollName, dequote);
+      }
+    }
+  }else if( pCollName->n>0 ){
     Expr *pNew = sqlite3ExprAlloc(pParse->db, TK_COLLATE, pCollName, dequote);
     if( pNew ){
       pNew->pLeft = pExpr;
diff --git a/src/whereexpr.c b/src/whereexpr.c
index e3c02deacd..9029ff1810 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1215,11 +1215,9 @@ static void exprAnalyzeExists(
   if( pInLhs==pEq->pLeft ){
     pRet = pEq->pRight;
   }else{
+    CollSeq *p = sqlite3ExprCompareCollSeq(pParse, pEq);
+    pInLhs = sqlite3ExprAddCollateString(pParse, pInLhs, p?p->zName:"BINARY");
     pRet = pEq->pLeft;
-    if( pRet->op!=TK_VECTOR ){
-      CollSeq *p = sqlite3ExprCompareCollSeq(pParse, pEq);
-      pInLhs = sqlite3ExprAddCollateString(pParse, pInLhs, p?p->zName:"BINARY");
-    }
   }
 
   assert( pDup->pLeft==0 );
diff --git a/test/exists2.test b/test/exists2.test
index a28e5daaef..c4fc9dc373 100644
--- a/test/exists2.test
+++ b/test/exists2.test
@@ -105,16 +105,16 @@ do_execsql_eqp_test 1.7 {
 #
 reset_db
 do_execsql_test 2.0 {
-  CREATE TABLE t3(a TEXT PRIMARY KEY, b TEXT) WITHOUT ROWID;
-  CREATE TABLE t4(c TEXT COLLATE nocase);
+  CREATE TABLE t3(a TEXT PRIMARY KEY, b TEXT, x INT) WITHOUT ROWID;
+  CREATE TABLE t4(c TEXT COLLATE nocase, y INT);
 
-  INSERT INTO t3 VALUES('one', 'i');
-  INSERT INTO t3 VALUES('two', 'ii');
-  INSERT INTO t3 VALUES('three', 'iii');
-  INSERT INTO t3 VALUES('four', 'iv');
-  INSERT INTO t3 VALUES('five', 'v');
+  INSERT INTO t3 VALUES('one', 'i', 1);
+  INSERT INTO t3 VALUES('two', 'ii', 2);
+  INSERT INTO t3 VALUES('three', 'iii', 3);
+  INSERT INTO t3 VALUES('four', 'iv', 4);
+  INSERT INTO t3 VALUES('five', 'v', 5);
 
-  INSERT INTO t4 VALUES('FIVE'), ('four'), ('TWO'), ('one');
+  INSERT INTO t4 VALUES('FIVE',5), ('four',4), ('TWO',2), ('one',1);
 }
 
 do_execsql_test 2.1 { SELECT a FROM t3, t4 WHERE a=c } {four one}
@@ -137,7 +137,7 @@ do_execsql_eqp_test 2.4 {
 }
 
 do_execsql_test 2.5 {
-  CREATE INDEX t3anc ON t3(a COLLATE nocase);
+  CREATE INDEX t3anc ON t3(a COLLATE nocase, x);
 }
 
 do_execsql_eqp_test 2.6 {
@@ -147,6 +147,9 @@ do_execsql_eqp_test 2.6 {
 } {
   five four one two
 }
+do_execsql_test 2.6a {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE (c,y)=(a,x))
+} {five four one two}
 
 do_execsql_eqp_test 2.7 {
   SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE a=c)
@@ -155,6 +158,11 @@ do_execsql_eqp_test 2.7 {
 } {
   four one
 }
+do_execsql_test 2.7a {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE (a,x)=(c,y))
+} {
+  four one
+}
 
 # EXISTS clauses using vector expressions in the WHERE clause.
 #

From 9fcc8c69bbf0af6da7f3e767ddadd1aa7bf28bbe Mon Sep 17 00:00:00 2001
From: drh <>
Date: Sun, 17 Jan 2021 00:13:12 +0000
Subject: [PATCH 12/13] Minor simplification of the EXISTS-to-IN logic.

FossilOrigin-Name: cac90a9f4ab0a8f3ff77ee1f8549213c2f97169fc3469e55d57caa564079ce2a
---
 manifest        | 12 ++++++------
 manifest.uuid   |  2 +-
 src/whereexpr.c |  8 +++-----
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/manifest b/manifest
index 2755d47c82..51ebfdca8d 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Improved\shandling\sof\svector\sequalities\sin\sthe\sEXISTS-to-IN\stranslator.
-D 2021-01-16T20:22:11.928
+C Minor\ssimplification\sof\sthe\sEXISTS-to-IN\slogic.
+D 2021-01-17T00:13:12.097
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 9fdbed19035077e41ca993ab469114e9b6b0746c18ea4e7675a850713b35fc72
+F src/whereexpr.c 9886a16b52af66e01ded9e69e3e2913f25d8e34bdeaa5e583d7c8c9a1ffe71d2
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1897,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 87e78a19bb3ae1caf57aeeae53a5ab4efdccb57265f25d5c19b62eae53747aff
-R 9040bb485a8bcb3beab221382ed76aaa
+P ef49ee4a3766146963bfb6b013472f9836afb9c5b0d21a8533871cf961139e38
+R ed5d5749a7ed1103ef3bdb4ce2a908bc
 U drh
-Z 15d0a474b0220437a1e81a3ea0fc01b3
+Z beb39ea924321eafaa423b5e3b964772
diff --git a/manifest.uuid b/manifest.uuid
index 773b82c6ef..7186b19c6e 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ef49ee4a3766146963bfb6b013472f9836afb9c5b0d21a8533871cf961139e38
\ No newline at end of file
+cac90a9f4ab0a8f3ff77ee1f8549213c2f97169fc3469e55d57caa564079ce2a
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 9029ff1810..584d2d35f5 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1254,11 +1254,9 @@ static void exprAnalyzeExists(
   }
 #endif
   idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
-  if( idxNew ){
-    exprAnalyze(pSrc, pWC, idxNew);
-    markTermAsChild(pWC, idxNew, idxTerm);
-    pWC->a[idxTerm].wtFlags |= TERM_COPIED;
-  }
+  exprAnalyze(pSrc, pWC, idxNew);
+  markTermAsChild(pWC, idxNew, idxTerm);
+  pWC->a[idxTerm].wtFlags |= TERM_COPIED;
 }
 
 /*

From 06afa291cfc887c7a5592542c770184db6732814 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Mon, 18 Jan 2021 00:11:20 +0000
Subject: [PATCH 13/13] More comments on the EXISTS-to-IN optimization logic.

FossilOrigin-Name: 92cc29099f796f5f244dd80ee431c48d36d01eaece6f150119ead5ecd14eaae1
---
 manifest        | 12 ++++++------
 manifest.uuid   |  2 +-
 src/whereexpr.c | 37 +++++++++++++++++++++++++------------
 3 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/manifest b/manifest
index 51ebfdca8d..c51fc6703b 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Minor\ssimplification\sof\sthe\sEXISTS-to-IN\slogic.
-D 2021-01-17T00:13:12.097
+C More\scomments\son\sthe\sEXISTS-to-IN\soptimization\slogic.
+D 2021-01-18T00:11:20.813
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -630,7 +630,7 @@ F src/walker.c d9c4e454ebb9499e908aa62d55b8994c375cf5355ac78f60d45af17f7890701c
 F src/where.c 0e6abb22a2323fec80b450825593c26a2ad8f4815d1ee3af9969d8f6144bf681
 F src/whereInt.h 9a3f577619f07700d16d89eeb2f3d94d6b7ed7f109c2dacf0ce8844921549506
 F src/wherecode.c a3a1aff30fe99a818d8e7c607980f033f40c68d890e03ed25838b9dbb7908bee
-F src/whereexpr.c 9886a16b52af66e01ded9e69e3e2913f25d8e34bdeaa5e583d7c8c9a1ffe71d2
+F src/whereexpr.c a022b4f447c0fb0674e172a9a303537ea5055df60d579f99cec7ead18e8c453f
 F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1897,7 +1897,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ef49ee4a3766146963bfb6b013472f9836afb9c5b0d21a8533871cf961139e38
-R ed5d5749a7ed1103ef3bdb4ce2a908bc
+P cac90a9f4ab0a8f3ff77ee1f8549213c2f97169fc3469e55d57caa564079ce2a
+R f533358ab2d88dffa58abcd3bcdbe4bd
 U drh
-Z beb39ea924321eafaa423b5e3b964772
+Z 7271ac9ea9a27eaec7cf5d0a637bfec4
diff --git a/manifest.uuid b/manifest.uuid
index 7186b19c6e..689f037d90 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-cac90a9f4ab0a8f3ff77ee1f8549213c2f97169fc3469e55d57caa564079ce2a
\ No newline at end of file
+92cc29099f796f5f244dd80ee431c48d36d01eaece6f150119ead5ecd14eaae1
\ No newline at end of file
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 584d2d35f5..5cfdad67c1 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -1036,13 +1036,26 @@ static int exprUsesSrclistSelectCb(Walker *p, Select *pSelect){
 ** This function always returns true if expression pExpr contains
 ** a sub-select.
 **
-** If there is no sub-select and bUses is 1, then true is returned
-** if the expression contains at least one TK_COLUMN node that refers
-** to a table in pSrc.
+** If there is no sub-select in pExpr, then return true if pExpr
+** contains a TK_COLUMN node for a table that is (bUses==1)
+** or is not (bUses==0) in pSrc.
 **
-** Or, if there is no sub-select and bUses is 0, then true is returned
-** if the expression contains at least one TK_COLUMN node that refers
-** to a table that is not in pSrc.
+** Said another way:
+**
+**   bUses      Return     Meaning
+**   --------   ------     ------------------------------------------------
+**
+**   bUses==1   true       pExpr contains either a sub-select or a
+**                         TK_COLUMN referencing pSrc.
+**
+**   bUses==1   false      pExpr contains no sub-selects and all TK_COLUMN
+**                         nodes reference tables not found in pSrc
+**
+**   bUses==0   true       pExpr contains either a sub-select or a TK_COLUMN
+**                         that references a table not in pSrc.
+**
+**   bUses==0   false      pExpr contains no sub-selects and all TK_COLUMN
+**                         nodes reference pSrc
 */
 static int exprUsesSrclist(SrcList *pSrc, Expr *pExpr, int bUses){
   Walker sWalker;
@@ -1059,11 +1072,11 @@ static int exprUsesSrclist(SrcList *pSrc, Expr *pExpr, int bUses){
 ** expression tree.
 */
 struct ExistsToInCtx {
-  SrcList *pSrc;
-  Expr *pInLhs;
-  Expr *pEq;
-  Expr **ppAnd;
-  Expr **ppParent;
+  SrcList *pSrc;    /* The tables in an EXISTS(SELECT ... FROM <here> ...) */
+  Expr *pInLhs;     /* OUT:  Use this as the LHS of the IN operator */
+  Expr *pEq;        /* OUT:  The == term that include pInLhs */
+  Expr **ppAnd;     /* OUT:  The AND operator that includes pEq as a child */
+  Expr **ppParent;  /* The AND operator currently being examined */
 };
 
 /*
@@ -1131,7 +1144,7 @@ static int exprExistsToInIter(struct ExistsToInCtx *p, Expr **ppExpr){
 ** node within the WHERE expression tree.
 */
 static Expr *exprAnalyzeExistsFindEq(
-  Select *pSel,
+  Select *pSel,                   /* The SELECT of the EXISTS */
   Expr **ppEq,                    /* OUT: == node from WHERE clause */
   Expr ***pppAnd                  /* OUT: Pointer to parent of ==, if any */
 ){