From 6918095d816d8e0eef2d3db520c1e49348020634 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Thu, 25 Jun 2015 13:03:10 +0000
Subject: [PATCH] Enhance the Btree object to remember whether or not it is
 holding an Incrblob cursor.  Use this knowledge to improve performance in the
 common case where it does not.

FossilOrigin-Name: 476b11563c08c6d9c0abd69e4d865c4edcdd45f5
---
 manifest       | 14 +++++++-------
 manifest.uuid  |  2 +-
 src/btree.c    | 15 +++++++++------
 src/btreeInt.h |  1 +
 4 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/manifest b/manifest
index 1ee479c8b3..d294c30b1e 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Remove\sa\sline\sof\scode\sthat\sdoesn't\sdo\sany\suseful\swork.
-D 2015-06-25T02:26:45.202
+C Enhance\sthe\sBtree\sobject\sto\sremember\swhether\sor\snot\sit\sis\sholding\san\nIncrblob\scursor.\s\sUse\sthis\sknowledge\sto\simprove\sperformance\sin\sthe\scommon\ncase\swhere\sit\sdoes\snot.
+D 2015-06-25T13:03:10.554
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 1063c58075b7400d93326b0eb332b48a54f53025
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -192,9 +192,9 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c a0eaf1139bbbb1f98abee448fb705c384a596075
+F src/btree.c 8a4109bdc6993507e95e3b377917a51a33b47027
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
-F src/btreeInt.h 6ece2dd9c8e2eac05f0a8ded8772a44e96486c65
+F src/btreeInt.h fdd1aff02fb2a63812bd95716e7f579fc3759107
 F src/build.c b3f15255d5b16e42dafeaa638fd4f8a47c94ed70
 F src/callback.c 7b44ce59674338ad48b0e84e7b72f935ea4f68b0
 F src/complete.c a5cf5b4b56390cfb7b8636e8f7ddef90258dd575
@@ -1286,7 +1286,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P fad0eacc64b1810f60cab73bc88ba380f99e4b2d
-R 1be92db979daaba09154bd51cdee9df8
+P 3ee888beb974e015bd11ae79381b208eaa310f6f
+R 0fbef3ab0e1cedf4de8407e78df7b662
 U drh
-Z 4ec67a5cc5de328f0e5fd8e756e47fd0
+Z 765ae28d6062dc43145a9a4098bd20e0
diff --git a/manifest.uuid b/manifest.uuid
index 86ab9a1da6..d2554ebcab 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-3ee888beb974e015bd11ae79381b208eaa310f6f
\ No newline at end of file
+476b11563c08c6d9c0abd69e4d865c4edcdd45f5
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 50f5bfd916..23af2570cb 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -490,13 +490,15 @@ static void invalidateIncrblobCursors(
   int isClearTable        /* True if all rows are being deleted */
 ){
   BtCursor *p;
-  BtShared *pBt = pBtree->pBt;
+  if( pBtree->hasIncrblobCur==0 ) return;
   assert( sqlite3BtreeHoldsMutex(pBtree) );
-  for(p=pBt->pCursor; p; p=p->pNext){
-    if( (p->curFlags & BTCF_Incrblob)!=0
-     && (isClearTable || p->info.nKey==iRow)
-    ){
-      p->eState = CURSOR_INVALID;
+  pBtree->hasIncrblobCur = 0;
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    if( (p->curFlags & BTCF_Incrblob)!=0 ){
+      pBtree->hasIncrblobCur = 1;
+      if( isClearTable || p->info.nKey==iRow ){
+        p->eState = CURSOR_INVALID;
+      }
     }
   }
 }
@@ -9450,6 +9452,7 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
 */
 void sqlite3BtreeIncrblobCursor(BtCursor *pCur){
   pCur->curFlags |= BTCF_Incrblob;
+  pCur->pBtree->hasIncrblobCur = 1;
 }
 #endif
 
diff --git a/src/btreeInt.h b/src/btreeInt.h
index 50c7db3a19..6fc8c45ea3 100644
--- a/src/btreeInt.h
+++ b/src/btreeInt.h
@@ -353,6 +353,7 @@ struct Btree {
   u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
   u8 sharable;       /* True if we can share pBt with another db */
   u8 locked;         /* True if db currently has pBt locked */
+  u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
   int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
   int nBackup;       /* Number of backup operations reading this btree */
   u32 iDataVersion;  /* Combines with pBt->pPager->iDataVersion */
-- 
2.47.2