Improved VDBE comments on the ANALYZE code generator. This change

also fixes a harmless use of an uninitialized integer variable as an input
to the %d format on a VDBE comment.

FossilOrigin-Name: 1cb248a3fc4c35c5bc3993b554edcccaa5c5e91570af67ebb99643a15221ae33

manifest

@@ -1,5 +1,5 @@
-C Enhancements\sto\sthe\sincremental\sbuild\ssupport\sfor\sMSVC.
+C Improved\sVDBE\scomments\son\sthe\sANALYZE\scode\sgenerator.\s\sThis\schange\nalso\sfixes\sa\sharmless\suse\sof\san\suninitialized\sinteger\svariable\sas\san\sinput\nto\sthe\s%d\sformat\son\sa\sVDBE\scomment.
-D 2020-05-29T21:06:52.599
+D 2020-05-30T00:30:08.761
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -468,7 +468,7 @@ F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
 F src/alter.c 826bc4561456094cf758f095776026f25892a2bb3a7cd86742323267dc9bdb5f
-F src/analyze.c 953a6c43870ccaf080597244e1eeb4dc2ff6cb84f9501b24e46323de36970b61
+F src/analyze.c 2c77bcbb8651ccced4a8cdaf8d997663813b2967787070fa26d0360de2ee4367
 F src/attach.c ff2daea0fe62080192e3f262670e4f61f5a86c1e7bea9cec34e960fe79852aa1
 F src/auth.c a3d5bfdba83d25abed1013a8c7a5f204e2e29b0c25242a56bc02bb0c07bf1e06
 F src/backup.c b1c90cd4110248c8e1273ff4578d3a84c0c34725e1b96dacd4a6294a908702de
@@ -1866,7 +1866,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5865d2f2d0333024366ecf1d919535fd4ec05c637feff16d75028ccdc8db4b50
+P 2e25d915bcb8d6f1747f9befdef64d2e0e495cc6c5948a8eff5d0097b6613d06
-R ea1f39211518f41f5c2b12c4cd8c40f2
+R 2675b53bd7c59c171705e1753c06ddb1
-U mistachkin
+U drh
-Z 0c710e2dd8d54ec195365654b7322b90
+Z 4e29343ffa9662765735989ac396bab3

manifest.uuid

@@ -1 +1 @@
-2e25d915bcb8d6f1747f9befdef64d2e0e495cc6c5948a8eff5d0097b6613d06
+1cb248a3fc4c35c5bc3993b554edcccaa5c5e91570af67ebb99643a15221ae33

src/analyze.c

@@ -951,6 +951,30 @@ static void callStatGet(Parse *pParse, int regStat, int iParam, int regOut){
                              &statGetFuncdef, 0);
 }
 
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+/* Add a comment to the most recent VDBE opcode that is the name
+** of the k-th column of the pIdx index.
+*/
+static void analyzeVdbeCommentIndexWithColumnName(
+  Vdbe *v,         /* Prepared statement under construction */
+  Index *pIdx,     /* Index whose column is being loaded */
+  int k            /* Which column index */
+){
+  int i;           /* Index of column in the table */
+  assert( k>=0 && k<pIdx->nColumn );
+  i = pIdx->aiColumn[k];
+  if( NEVER(i==XN_ROWID) ){
+    VdbeComment((v,"%s.rowid",pIdx->zName));
+  }else if( i==XN_EXPR ){
+    VdbeComment((v,"%s.expr(%d)",pIdx->zName, k));
+  }else{
+    VdbeComment((v,"%s.%s", pIdx->zName, pIdx->pTable->aCol[i].zName));
+  }
+}
+#else
+# define analyzeVdbeCommentIndexWithColumnName(a,b,c)
+#endif /* SQLITE_DEBUG */
+
 /*
 ** Generate code to do an analysis of all indices associated with
 ** a single table.
@@ -1167,7 +1191,7 @@ static void analyzeOneTable(
         char *pColl = (char*)sqlite3LocateCollSeq(pParse, pIdx->azColl[i]);
         sqlite3VdbeAddOp2(v, OP_Integer, i, regChng);
         sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regTemp);
-        VdbeComment((v, "%s.column(%d)", pIdx->zName, i));
+        analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
         aGotoChng[i] = 
         sqlite3VdbeAddOp4(v, OP_Ne, regTemp, 0, regPrev+i, pColl, P4_COLLSEQ);
         sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
@@ -1188,7 +1212,7 @@ static void analyzeOneTable(
       for(i=0; i<nColTest; i++){
         sqlite3VdbeJumpHere(v, aGotoChng[i]);
         sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regPrev+i);
-        VdbeComment((v, "%s.column(%d)", pIdx->zName, i));
+        analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
       }
       sqlite3VdbeResolveLabel(v, endDistinctTest);
       sqlite3DbFree(db, aGotoChng);
@@ -1214,7 +1238,7 @@ static void analyzeOneTable(
           k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[j]);
           assert( k>=0 && k<pIdx->nColumn );
           sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, regKey+j);
-          VdbeComment((v, "%s.column(%d)", pIdx->zName, i));
+          analyzeVdbeCommentIndexWithColumnName(v,pIdx,k);
         }
         sqlite3VdbeAddOp3(v, OP_MakeRecord, regKey, pPk->nKeyCol, regRowid);
         sqlite3ReleaseTempRange(pParse, regKey, pPk->nKeyCol);