From: drh <drh@noemail.net>
Date: Sat, 11 May 2019 19:36:03 +0000 (+0000)
Subject: A new implementation for the sqlite3ExprImpliesExpr() theorem prover that
X-Git-Tag: version-3.29.0~105
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c51cf8642f867050c8cb9e330582605dabeff76c;p=thirdparty%2Fsqlite.git

A new implementation for the sqlite3ExprImpliesExpr() theorem prover that
does a better job of answering TRUE to "(NOT A) OR B" when B is a NOT NULL
expression.

FossilOrigin-Name: b3413197f57711f04102d8cc6ff1e8ddbe0f5f2bcb6e1989cf314fa97f0ff7f1
---

diff --git a/manifest b/manifest
index 2f69eeca87..2b05533af9 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C When\sconsidering\spartial\sindexes,\sdo\snot\sassume\sthat\sa\s"CASE\sx\s..."\sexpression\simplies\s"x\sIS\sNOT\sNULL".
-D 2019-05-11T16:14:42.493
+C A\snew\simplementation\sfor\sthe\ssqlite3ExprImpliesExpr()\stheorem\sprover\sthat\ndoes\sa\sbetter\sjob\sof\sanswering\sTRUE\sto\s"(NOT\sA)\sOR\sB"\swhen\sB\sis\sa\sNOT\sNULL\nexpression.
+D 2019-05-11T19:36:03.376
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -473,7 +473,7 @@ F src/date.c ebe1dc7c8a347117bb02570f1a931c62dd78f4a2b1b516f4837d45b7d6426957
 F src/dbpage.c 135eb3b5e74f9ef74bde5cec2571192c90c86984fa534c88bf4a055076fa19b7
 F src/dbstat.c c12833de69cb655751487d2c5a59607e36be1c58ba1f4bd536609909ad47b319
 F src/delete.c d08c9e01a2664afd12edcfa3a9c6578517e8ff8735f35509582693adbe0edeaf
-F src/expr.c de746e2fc5ee48441b1210fba9a39160981718430e6a75b3a2ba29a99957cb71
+F src/expr.c a41e5a03d60e2d99a8eac1535f21258e3833b29a3f52789e76284d97b54bed5f
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c 0e14d4bef8eac2d87bbd517e492d9084c65008d117823f8922c5e7b2b599bd33
 F src/func.c 08d6d07d138735dd79f12a2b0c623d1dc9270d0eea61b8be584625391ef84475
@@ -1825,7 +1825,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0ba6d709b50d92db1542f2ff30535a80184b00dadf759d51e5cae7a6e37b1764
-R eed45e78e88ca93286620dd3277355ae
-U dan
-Z 697971a2288076e83fc4830e959d8147
+P 1b24303220b7b4f59520176a0150fc619c668865450b4fdaa9ce4113a56e9687
+R a0d6bf1f0575775c4809b4d1861fc898
+U drh
+Z 5104434a3315d7327fcd08f55bb43328
diff --git a/manifest.uuid b/manifest.uuid
index a33bef3c01..dad98559cb 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-1b24303220b7b4f59520176a0150fc619c668865450b4fdaa9ce4113a56e9687
\ No newline at end of file
+b3413197f57711f04102d8cc6ff1e8ddbe0f5f2bcb6e1989cf314fa97f0ff7f1
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index 05b50c1e62..a905c28c9b 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -4908,6 +4908,76 @@ int sqlite3ExprCompareSkip(Expr *pA, Expr *pB, int iTab){
              iTab);
 }
 
+/*
+** Return non-zero if Expr p can only be true if pNN is not NULL.
+*/
+static int exprImpliesNotNull(
+  Parse *pParse,      /* Parsing context */
+  Expr *p,            /* The expression to be checked */
+  Expr *pNN,          /* The expression that is NOT NULL */
+  int iTab,           /* Table being evaluated */
+  int seenNot         /* True if p is an operand of NOT */
+){
+  assert( p );
+  assert( pNN );
+  if( sqlite3ExprCompare(pParse, p, pNN, iTab)==0 ) return 1;
+  switch( p->op ){
+    case TK_IN: {
+      if( seenNot && ExprHasProperty(p, EP_xIsSelect) ) return 0;
+      assert( ExprHasProperty(p,EP_xIsSelect)
+           || (p->x.pList!=0 && p->x.pList->nExpr>0) );
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
+    }
+    case TK_BETWEEN: {
+      ExprList *pList = p->x.pList;
+      assert( pList!=0 );
+      assert( pList->nExpr==2 );
+      if( seenNot ) return 0;
+      if( exprImpliesNotNull(pParse, pList->a[0].pExpr, pNN, iTab, seenNot)
+       || exprImpliesNotNull(pParse, pList->a[1].pExpr, pNN, iTab, seenNot)
+      ){
+        return 1;
+      }
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
+    }
+    case TK_EQ:
+    case TK_NE:
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_PLUS:
+    case TK_MINUS:
+    case TK_STAR:
+    case TK_REM:
+    case TK_BITAND:
+    case TK_BITOR:
+    case TK_SLASH:
+    case TK_LSHIFT:
+    case TK_RSHIFT: 
+    case TK_CONCAT: {
+      if( exprImpliesNotNull(pParse, p->pRight, pNN, iTab, seenNot) ) return 1;
+      /* Fall thru into the next case */
+    }
+    case TK_SPAN:
+    case TK_COLLATE:
+    case TK_BITNOT:
+    case TK_UPLUS:
+    case TK_UMINUS: {
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
+    }
+    case TK_TRUTH: {
+      if( seenNot ) return 0;
+      if( p->op2!=TK_IS ) return 0;
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
+    }
+    case TK_NOT: {
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
+    }
+  }
+  return 0;
+}
+
 /*
 ** Return true if we can prove the pE2 will always be true if pE1 is
 ** true.  Return false if we cannot complete the proof or if pE2 might
@@ -4944,15 +5014,9 @@ int sqlite3ExprImpliesExpr(Parse *pParse, Expr *pE1, Expr *pE2, int iTab){
     return 1;
   }
   if( pE2->op==TK_NOTNULL
-   && pE1->op!=TK_ISNULL
-   && pE1->op!=TK_IS
-   && pE1->op!=TK_ISNOT
-   && pE1->op!=TK_OR
-   && pE1->op!=TK_CASE
+   && exprImpliesNotNull(pParse, pE1, pE2->pLeft, iTab, 0)
   ){
-    Expr *pX = sqlite3ExprSkipCollate(pE1->pLeft);
-    testcase( pX!=pE1->pLeft );
-    if( sqlite3ExprCompare(pParse, pX, pE2->pLeft, iTab)==0 ) return 1;
+    return 1;
   }
   return 0;
 }