Simplification of the WHERE loop code generator for NULLS LAST saves a

few CPU cycles and about a hundred bytes of code space.

FossilOrigin-Name: e3ed2f496f51234a8f81d90d47ba603b06dbed38b8bd8f1934294379cde74d3a

diff --git a/manifest b/manifest
index 6962dd393e67b7dc7d043d7c6c2412300afd6e97..46a935e6098c16180b2a7f7778cbfd0bc615a562 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Invert\sthe\smeaning\sof\sthe\sregBignull\sflag\sso\sthat\sit\sis\s1\swhen\sdoing\sthe\nnormal\sscan\sand\s1\swhen\sscanning\snulls.\s\sThis\senables\sthe\sre-do\sjump\sat\sthe\nbottom\sof\sthe\sloop\sto\sbe\scoded\swith\sa\ssingle\sOP_IfNotZero\sopcode,\srather\nthan\sa\ssequence\sof\sOP_If,\sOP_Integer,\sOP_Goto.
-D 2019-08-23T13:32:03.306
+C Simplification\sof\sthe\sWHERE\sloop\scode\sgenerator\sfor\sNULLS\sLAST\ssaves\sa\nfew\sCPU\scycles\sand\sabout\sa\shundred\sbytes\sof\scode\sspace.
+D 2019-08-23T16:12:20.533
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -611,7 +611,7 @@ F src/wal.h 606292549f5a7be50b6227bd685fa76e3a4affad71bb8ac5ce4cb5c79f6a176a
 F src/walker.c d5a94907dcac990e31976be9dc769d17f6a806782593d6aec9d760ee01ec22cd
 F src/where.c 10e21ac338582a4f87b2d09f09dd812c9bda0a0c4c456f54daeeee355afae733
 F src/whereInt.h 4a296fd4fa79fdcbc2b5e8c1b898901617655811223e1082b899c23ecb092217
-F src/wherecode.c c02ff23ea48b8980d003817bd412e3ce7ce4982159a090566a24cb6101688a9d
+F src/wherecode.c f8ba85888b8a6843bce84e7e21f61d6c043c21c888871ad84fb911f45671e95d
 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 649b08ead50f10a9ec0357a5e1ed020195d9f93be61ef703ea036a8e53f07a34
-R c7fec8ea82d2ec3c4ef608bd58d88fd0
+P bf875e1a259a4167694e06349458452dc36c1d38aa6843518d9ae46ce74e5559
+R f34508d6bf0c4c450df67caf81b0a3ce
 U drh
-Z 0dcd16d55adeefa06ece8236ed711d36
+Z 77866c600215002b5dd6dd0eeafd861f

diff --git a/manifest.uuid b/manifest.uuid
index 72e2aaa81194aa9ddf0e922d56f6b3a68c2d2542..c464a63a9768a7478049c2458d923d4859620cfb 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-bf875e1a259a4167694e06349458452dc36c1d38aa6843518d9ae46ce74e5559
\ No newline at end of file
+e3ed2f496f51234a8f81d90d47ba603b06dbed38b8bd8f1934294379cde74d3a
\ No newline at end of file

diff --git a/src/wherecode.c b/src/wherecode.c
index 2aff70554f951c9661522b0772bada7b2402da9d..c1304c8af19a21e62409cbfef1eac1029cfeb0d9 100644 (file)
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -1671,10 +1671,10 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       }
       bSeekPastNull = 0;
     }else if( bSeekPastNull ){
-      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
-      nConstraint++;
       startEq = 0;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
       start_constraints = 1;
+      nConstraint++;
     }else if( regBignull ){
       sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
       start_constraints = 1;
@@ -1705,30 +1705,20 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
       VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
 
+      assert( bSeekPastNull==0 || bStopAtNull==0 );
       if( regBignull ){
+        assert( bSeekPastNull==1 || bStopAtNull==1 );
+        assert( bStopAtNull==startEq );
         sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
-        if( bStopAtNull ){
-          start_constraints = (nConstraint>1);
-          op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
-          sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint-1);
-          VdbeCoverage(v);
-          VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
-          VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
-          VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
-          VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
-          VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
-          VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
-        }else{
-          op = aStartOp[(start_constraints<<2) + ((!startEq)<<1) + bRev];
-          sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
-          VdbeCoverage(v);
-          VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
-          VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
-          VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
-          VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
-          VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
-          VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
-        }
+        op = aStartOp[(nConstraint>1)*4 + 2 + bRev];
+        sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, 
+                             nConstraint-startEq);
+        VdbeCoverage(v);
+        VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
+        VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
+        VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
+        VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
+        assert( op==OP_Rewind || op==OP_Last || op==OP_SeekGE || op==OP_SeekLE);
       }
     }