From: drh <drh@noemail.net>
Date: Mon, 5 Sep 2016 15:02:41 +0000 (+0000)
Subject: Simplifications to the SQLITE_KEEPNULL flag on VDBE comparison operators.
X-Git-Tag: version-3.15.0~110^2~15
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3fffbf932719916b9a6564280b1254ce4f6c5012;p=thirdparty%2Fsqlite.git

Simplifications to the SQLITE_KEEPNULL flag on VDBE comparison operators.

FossilOrigin-Name: 96269f0179a7d8fa44ee278cef362962368c59ef
---

diff --git a/manifest b/manifest
index 22dc90908e..050f3253f6 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Do\svector\scomparison\ssize\schecking\searly\s-\sat\sname\sresolution\stime\s-\sto\nforestall\sfuture\sproblems.
-D 2016-09-05T12:12:56.221
+C Simplifications\sto\sthe\sSQLITE_KEEPNULL\sflag\son\sVDBE\scomparison\soperators.
+D 2016-09-05T15:02:41.820
 F Makefile.in cfd8fb987cd7a6af046daa87daa146d5aad0e088
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 5017381e4853b1472e01d5bb926be1268eba429c
@@ -451,7 +451,7 @@ F src/update.c 8179e699dbd45b92934fd02d3d8e3732e8da8802
 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c
 F src/util.c 810ec3f22e2d1b62e66c30fe3621ebdedd23584d
 F src/vacuum.c 913970b9d86dd6c2b8063ef1af421880f1464ec3
-F src/vdbe.c d8fb59a3ef10636df2447f55c1e82be7b8ad1604
+F src/vdbe.c 3148d5d47816c5ad2ed3c62beb3086cbbcaab107
 F src/vdbe.h 67bc551f7faf04c33493892e4b378aada823ed10
 F src/vdbeInt.h c59381049af5c7751a83456c39b80d1a6fde1f9d
 F src/vdbeapi.c a32d61b7dd05e6890d8fd44d2805f55e2f5ba9f3
@@ -1522,8 +1522,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 42670935aba152ba774c2a8bdcbe72b943309d68 56562a0346170cf7b72445976864b058437a8ac3
-R 9ea9c6d7e55a2e73634a9a6491229b09
-T +closed 56562a0346170cf7b72445976864b058437a8ac3
+P ae127bcc0a5827786853f47b229021435d6098d7
+R b6639bee17b9273a45c7e5e2da3019f4
 U drh
-Z c545a18fc0ce61b83efad3cc467f4a6a
+Z a8418630f7d7128d87f9b291fb48ec92
diff --git a/manifest.uuid b/manifest.uuid
index a64a078eae..1973c3697e 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ae127bcc0a5827786853f47b229021435d6098d7
\ No newline at end of file
+96269f0179a7d8fa44ee278cef362962368c59ef
\ No newline at end of file
diff --git a/src/vdbe.c b/src/vdbe.c
index 443ecbce1d..c3c9c607cb 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -1912,7 +1912,8 @@ case OP_Cast: {                  /* in1 */
 ** the SQLITE_NULLEQ flag were omitted from P5.
 **
 ** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
-** content of r[P2] is only set to 1 (true) if it was not previously NULL.
+** content of r[P2] is only changed if the new value is NULL or 0 (false).
+** In other words, a prior r[P2] value will not be overwritten by 1 (true).
 */
 /* Opcode: Ne P1 P2 P3 P4 P5
 ** Synopsis: IF r[P3]!=r[P1]
@@ -1922,7 +1923,8 @@ case OP_Cast: {                  /* in1 */
 ** additional information.
 **
 ** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
-** content of r[P2] is only set to 0 (false) if it was not previously NULL.
+** content of r[P2] is only changed if the new value is NULL or 1 (true).
+** In other words, a prior r[P2] value will not be overwritten by 0 (false).
 */
 /* Opcode: Lt P1 P2 P3 P4 P5
 ** Synopsis: IF r[P3]<r[P1]
@@ -2086,11 +2088,20 @@ case OP_Ge: {             /* same as TK_GE, jump, in1, in3 */
     pOut = &aMem[pOp->p2];
     iCompare = res;
     res2 = res2!=0;  /* For this path res2 must be exactly 0 or 1 */
-    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 && (pOut->flags & MEM_Null)!=0 ){
+    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 ){
       /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
-      ** and prevents OP_Ne from overwriting NULL with 0. */
+      ** and prevents OP_Ne from overwriting NULL with 0.  This flag
+      ** is only used in contexts where either:
+      **   (1) op==OP_Eq && (r[P2]==NULL || r[P2]==0)
+      **   (2) op==OP_Ne && (r[P2]==NULL || r[P2]==1)
+      ** Therefore it is not necessary to check the content of r[P2] for
+      ** NULL. */
       assert( pOp->opcode==OP_Ne || pOp->opcode==OP_Eq );
       assert( res2==0 || res2==1 );
+      testcase( res2==0 && pOp->opcode==OP_Eq );
+      testcase( res2==1 && pOp->opcode==OP_Eq );
+      testcase( res2==0 && pOp->opcode==OP_Ne );
+      testcase( res2==1 && pOp->opcode==OP_Ne );
       if( (pOp->opcode==OP_Eq)==res2 ) break;
     }
     memAboutToChange(p, pOut);