From: drh <drh@noemail.net>
Date: Wed, 8 May 2019 19:06:59 +0000 (+0000)
Subject: Avoid an excess register allocation in UPDATE, when possible.  This improves
X-Git-Tag: version-3.29.0~135
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9e9374b2e20a2221f8fdfb940d6d82064d641283;p=thirdparty%2Fsqlite.git

Avoid an excess register allocation in UPDATE, when possible.  This improves
speed (slightly) and reduces the code footprint.

FossilOrigin-Name: 8658574e3f435f03a87c04f398bd05078ebc53ecb4a477d3b24902d701d935c4
---

diff --git a/manifest b/manifest
index de029bebe7..d67ef530f4 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\stests\sto\simprove\scode\scoverage\sof\sthe\sRBU\smodule.
-D 2019-05-08T18:49:51.870
+C Avoid\san\sexcess\sregister\sallocation\sin\sUPDATE,\swhen\spossible.\s\sThis\simproves\nspeed\s(slightly)\sand\sreduces\sthe\scode\sfootprint.
+D 2019-05-08T19:06:59.709
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -588,7 +588,7 @@ F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c d3615f0cbe4db5949503bf5916f3cd4fa5de855d5b4ef560f3b6dd5629423a1e
 F src/treeview.c 56724725c62a0d0f408f7c257475dc33309198afee36a1d18be1bc268b09055e
 F src/trigger.c bb034c08eca111e66a19cda045903a12547c1be2294b5570d794b869d9c44a73
-F src/update.c fb29c2eb1f52a5009fd0e00f5041fb6ae14a7f9a5048da220e45e804c61b3559
+F src/update.c 3cb9150d2cf661d938e2f1b1749945f3faa767f88febdb739ab1793bbf895ff2
 F src/upsert.c 0dd81b40206841814d46942a7337786932475f085716042d0cb2fc7791bf8ca4
 F src/utf.c 2f0fac345c7660d5c5bd3df9e9d8d33d4c27f366bcfb09e07443064d751a0507
 F src/util.c 5061987401c2e8003177fa30d73196aa036727c8f04bf36a2df0c82b1904a236
@@ -1825,7 +1825,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P eabe7f2d4ff0e0dd868dcab7ec1d4a9168a25f80d3a52f0eeea2f90bd33782f2
-R f38629c2df688919c2eea086352e406a
-U dan
-Z 0dea2404f0db0801946b811401465571
+P ecb56b75a0e66462acdcce285b93f9fc56944c42902d886d6bada419059519a9
+R 2b2161dc021eeafc304f534286be079c
+U drh
+Z 70eeee98b674ce1a62d7db850c161190
diff --git a/manifest.uuid b/manifest.uuid
index 8af2174662..d30e6c6835 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ecb56b75a0e66462acdcce285b93f9fc56944c42902d886d6bada419059519a9
\ No newline at end of file
+8658574e3f435f03a87c04f398bd05078ebc53ecb4a477d3b24902d701d935c4
\ No newline at end of file
diff --git a/src/update.c b/src/update.c
index 8bb9f8466a..bbeaa3d5ce 100644
--- a/src/update.c
+++ b/src/update.c
@@ -155,6 +155,7 @@ void sqlite3Update(
   Index *pIdx;           /* For looping over indices */
   Index *pPk;            /* The PRIMARY KEY index for WITHOUT ROWID tables */
   int nIdx;              /* Number of indices that need updating */
+  int nAllIdx;           /* Total number of indexes */
   int iBaseCur;          /* Base cursor number */
   int iDataCur;          /* Cursor for the canonical data btree */
   int iIdxCur;           /* Cursor for the first index */
@@ -355,7 +356,7 @@ void sqlite3Update(
   ** the key for accessing each index.
   */
   if( onError==OE_Replace ) bReplace = 1;
-  for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+  for(nAllIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nAllIdx++){
     int reg;
     if( chngKey || hasFK>1 || pIdx==pPk
      || indexWhereClauseMightChange(pIdx,aXRef,chngRowid)
@@ -375,10 +376,10 @@ void sqlite3Update(
         }
       }
     }
-    if( reg==0 ) aToOpen[j+1] = 0;
-    aRegIdx[j] = reg;
+    if( reg==0 ) aToOpen[nAllIdx+1] = 0;
+    aRegIdx[nAllIdx] = reg;
   }
-  aRegIdx[j] = ++pParse->nMem;  /* Register storing the table record */
+  aRegIdx[nAllIdx] = ++pParse->nMem;  /* Register storing the table record */
   if( bReplace ){
     /* If REPLACE conflict resolution might be invoked, open cursors on all 
     ** indexes in case they are needed to delete records.  */
@@ -393,7 +394,13 @@ void sqlite3Update(
 
   /* Allocate required registers. */
   if( !IsVirtual(pTab) ){
-    regRowSet = ++pParse->nMem;
+    /* For now, regRowSet and aRegIdx[nAllIdx] share the same register.
+    ** If regRowSet turns out to be needed, then aRegIdx[nAllIdx] will be
+    ** reallocated.  aRegIdx[nAllIdx] is the register in which the main
+    ** table record is written.  regRowSet holds the RowSet for the
+    ** two-pass update algorithm. */
+    assert( aRegIdx[nAllIdx]==pParse->nMem );
+    regRowSet = aRegIdx[nAllIdx];
     regOldRowid = regNewRowid = ++pParse->nMem;
     if( chngPk || pTrigger || hasFK ){
       regOld = pParse->nMem + 1;
@@ -523,6 +530,8 @@ void sqlite3Update(
     ** leave it in register regOldRowid.  */
     sqlite3VdbeAddOp2(v, OP_Rowid, iDataCur, regOldRowid);
     if( eOnePass==ONEPASS_OFF ){
+      /* We need to use regRowSet, so reallocate aRegIdx[nAllIdx] */
+      aRegIdx[nAllIdx] = ++pParse->nMem;
       sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, regOldRowid);
     }
   }else{