Extra VDBE comments in the NULLS LAST logic provide landmarks to help

understand the EXPLAIN output.

FossilOrigin-Name: 649b08ead50f10a9ec0357a5e1ed020195d9f93be61ef703ea036a8e53f07a34

diff --git a/manifest b/manifest
index d781ff2ecd8959401e4052e200f4f86ed1e0eea9..9403c98df39c2402d20fd67f2f8f49af5ab99c74 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sadditional\sVDBE\scoverage\smarcros.
-D 2019-08-22T21:13:56.537
+C Extra\sVDBE\scomments\sin\sthe\sNULLS\sLAST\slogic\sprovide\slandmarks\sto\shelp\nunderstand\sthe\sEXPLAIN\soutput.
+D 2019-08-23T13:08:49.776
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -609,9 +609,9 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c bbd6838bd79c0a32144d482fb0b6a9d2d1a252fb3b16d5005ec30f2f80413b0d
 F src/wal.h 606292549f5a7be50b6227bd685fa76e3a4affad71bb8ac5ce4cb5c79f6a176a
 F src/walker.c d5a94907dcac990e31976be9dc769d17f6a806782593d6aec9d760ee01ec22cd
-F src/where.c e954bdbd248e755ddbe0ff54b743a7b99eeb2d852d034b2176004a905c4128bc
-F src/whereInt.h 807766a6a92893dbba8a887e5b13466d2257ce07a84cf1be0aae2c41aee3bf4f
-F src/wherecode.c f8005a06f78bd396216b444280a78688198e9b3aaed582c8e7fc608d111b1d93
+F src/where.c cba20474827dfb3e6bfe7835635e0f018a67d4b8faef4c90d4f28b81b81a8915
+F src/whereInt.h cce97c33db637c027bd6f3601a5ff845bd65c833b6465e3b091d48f6a7f51268
+F src/wherecode.c 1700806bb5bb507ff3614d0836893f35a5a5c438087ee6f373f2ecdf32156d71
 F src/whereexpr.c 2757afbd5cfdbb420f9d0392e1bd5f5c0e33dee50a8c692befc7e502308e449f
 F src/window.c 3ea716bb0dd5ffc8cdbaa48baffc525958b51bc61b2afd73a56baccfcd7ceb2f
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@@ -1837,7 +1837,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 63e625c8eb06720eef30573aa562e38c90d228a9cf493f8bb59f09e50f0e3168
-R 3b31af6d2e0a85acf1bc0e1de0094280
+P d3531f5be7d3769689e2cd8bdc9bab5608759de027d44cc123996f32a4a89583
+R ab23b496c06c535da116ba045bb5e66a
 U drh
-Z 763e56944768007815dc6fe6b985fbdb
+Z 115e4fb3e71b36cfad63bc3458a08668

diff --git a/manifest.uuid b/manifest.uuid
index 34fc4dc3eee81180b54fb1207580097b3aaf4ffc..729790d69c6d1a727911b0b5345fa17d57ce973d 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-d3531f5be7d3769689e2cd8bdc9bab5608759de027d44cc123996f32a4a89583
\ No newline at end of file
+649b08ead50f10a9ec0357a5e1ed020195d9f93be61ef703ea036a8e53f07a34
\ No newline at end of file

diff --git a/src/where.c b/src/where.c
index 37daab67915c8394b673543383eda934470c3733..00aa5f36605add6564030d27ed2e1b65c88965d7 100644 (file)
--- a/src/where.c
+++ b/src/where.c
@@ -5219,9 +5219,11 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
       if( pLevel->regBignull ){
         sqlite3VdbeResolveLabel(v, pLevel->addrBignull);
         addr = sqlite3VdbeAddOp1(v, OP_If, pLevel->regBignull);
+        VdbeComment((v, "If NULL-scan done"));
         VdbeCoverage(v);
         sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->regBignull);
         sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->p2-1);
+        VdbeComment((v, "Do the NULL-scan"));
         sqlite3VdbeJumpHere(v, addr);
       }
 #ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT

diff --git a/src/whereInt.h b/src/whereInt.h
index f402a18f8c576787117b6539d1217442f3b39ef3..d1fc3515a5b6af3dd2be23aa222c6a55e8dd4579 100644 (file)
--- a/src/whereInt.h
+++ b/src/whereInt.h
@@ -71,7 +71,7 @@ struct WhereLevel {
   int addrCont;         /* Jump here to continue with the next loop cycle */
   int addrFirst;        /* First instruction of interior of the loop */
   int addrBody;         /* Beginning of the body of this loop */
-  int regBignull;       /* big-null flag register */
+  int regBignull;       /* big-null flag reg. True if NULLs not yet scanned */
   int addrBignull;      /* Jump here for next part of big-null scan */
 #ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
   u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */

diff --git a/src/wherecode.c b/src/wherecode.c
index 55ac394b651053c7148836b6c5a64e7332ac9fa8..12ed0d7af023c4868cacc2522e01fe8e81d1ece9 100644 (file)
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -1550,7 +1550,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
     u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
     int omitTable;               /* True if we use the index only */
-    int regBignull = 0;
+    int regBignull = 0;          /* big-null flag register */
 
     pIdx = pLoop->u.btree.pIndex;
     iIdxCur = pLevel->iIdxCur;
@@ -1691,6 +1691,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       }
       if( regBignull ){
         sqlite3VdbeAddOp2(v, OP_Integer, 0, regBignull);
+        VdbeComment((v, "NULL-scan flag"));
       }
 
       op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
@@ -1776,6 +1777,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     if( nConstraint ){
       if( regBignull ){
         sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+3);
+        VdbeComment((v, "If in NULL-scan"));
         VdbeCoverage(v);
       }
       op = aEndOp[bRev*2 + endEq];
@@ -1787,6 +1789,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     }
     if( regBignull ){
       sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+2);
+      VdbeComment((v, "If not in NULL-scan"));
       VdbeCoverage(v);
       if( bStopAtNull ){
         op = aEndOp[bRev*2 + 0];