Clarify some comments and add assert() and testcase() macros to the

replace-trigger recheck logic for ticket [c1e19e12046d23fe]

FossilOrigin-Name: 8c0042bd5ccd83f8794d19cbb1ec7564584f0dce54bfebc0ada00b836aca065f

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\sproblem\sin\sthe\slegacy\s".explain\son"\sformatting\swhen\sit\sis\sused\son\na\squery\swith\smore\sthan\s8\soutput\scolumns.
-D 2019-10-26T16:02:34.898
+C Clarify\ssome\scomments\sand\sadd\sassert()\sand\stestcase()\smacros\sto\sthe\nreplace-trigger\srecheck\slogic\sfor\sticket\s[c1e19e12046d23fe]
+D 2019-10-26T16:38:49.916
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -487,7 +487,7 @@ F src/hash.c 8d7dda241d0ebdafb6ffdeda3149a412d7df75102cecfc1021c98d6219823b19
 F src/hash.h 9d56a9079d523b648774c1784b74b89bd93fac7b365210157482e4319a468f38
 F src/hwtime.h 747c1bbe9df21a92e9c50f3bbec1de841dc5e5da
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
-F src/insert.c 0ac7d3441ead03a3a457ed5c5c0f7f3cc20d7b7a6822c14c95d820fa9a091b9c
+F src/insert.c 52b5fae35661c3b723c4c51000bc071d7eca5cf803ceb63752527db62134ad5f
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 4ddc65ae13c0d93db0ceedc8b14a28c8c260513448b0eb8c5a2ac375e3b6a85d
 F src/main.c 3e01f6a1c96643381b5f9d79e4ff7f2520bc5712197746fb0852283e78cccf66
@@ -1848,7 +1848,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 346bdd49fb93aa58e8bd14250974d8c0c32cc7e8317c8b12da1fa44db10d8a3a
-R 93c72ffd5e28250381ddc75e7592ec49
+P 070b49825c5f87cce15be4b758f0dfdd65226ec379465ca527a18706a1f3b8f4
+R 1028cc5a00baf8569b464c2a7604c8c5
 U drh
-Z ff4e0c1d87bc1e1e843d86b79db1d8fb
+Z 8bf83f381e575a0d62d743fe518a1706

manifest.uuid

@@ -1 +1 @@
-070b49825c5f87cce15be4b758f0dfdd65226ec379465ca527a18706a1f3b8f4
+8c0042bd5ccd83f8794d19cbb1ec7564584f0dce54bfebc0ada00b836aca065f

src/insert.c

@@ -1501,8 +1501,8 @@ void sqlite3GenerateConstraintChecks(
   **
   **   (1) Allocate register regTrigCnt and initialize it to zero.
   **       That register will count the number of replace triggers that
-  **       fire.  Constraint recheck only occurs if the number if positive.
-  **   (2) Initialize pTrigger to the set of all DELETE triggers.
+  **       fire.  Constraint recheck only occurs if the number is positive.
+  **   (2) Initialize pTrigger to the list of all DELETE triggers on pTab.
   **   (3) Initialize addrRecheck and lblRecheckOk
   **
   ** The uniqueness rechecking code will create a series of tests to run
@@ -1881,6 +1881,8 @@ void sqlite3GenerateConstraintChecks(
 
         assert( onError==OE_Replace );
         nConflictCk = sqlite3VdbeCurrentAddr(v) - addrConflictCk;
+        assert( nConflictCk>0 );
+        testcase( nConflictCk>1 );
         if( regTrigCnt ){
           sqlite3MultiWrite(pParse);
           nReplaceTrig++;
@@ -1909,7 +1911,7 @@ void sqlite3GenerateConstraintChecks(
           /* Copy the constraint check code from above, except change
           ** the constraint-ok jump destination to be the address of
           ** the next retest block */
-          while( nConflictCk>0 && !db->mallocFailed ){
+          while( nConflictCk>0 ){
             VdbeOp x;    /* Conflict check opcode to copy */
             /* The sqlite3VdbeAddOp4() call might reallocate the opcode array.
             ** Hence, make a complete copy of the opcode, rather than using
@@ -1956,6 +1958,7 @@ void sqlite3GenerateConstraintChecks(
 
   /* Recheck all uniqueness constraints after replace triggers have run */
   testcase( regTrigCnt!=0 && nReplaceTrig==0 );
+  assert( regTrigCnt!=0 || nReplaceTrig==0 );
   if( nReplaceTrig ){
     sqlite3VdbeAddOp2(v, OP_IfNot, regTrigCnt, lblRecheckOk);VdbeCoverage(v);
     if( !pPk ){