From c930b405f0717d5f8626dd846f3ab1d2a7243195 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Tue, 8 Jan 2019 15:18:24 +0000
Subject: [PATCH] Performance improvement on the instr() function, especially
 for large haystacks.

FossilOrigin-Name: ce51f1a2b6a1789a5876e01cf829e45d84f3851d135a2fa5c44a56f948673a60
---
 manifest      | 12 ++++++------
 manifest.uuid |  2 +-
 src/func.c    |  6 +++++-
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/manifest b/manifest
index 87e96b2064..8935452168 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\spossible\smemory\sleak\swhen\strying\sto\sUPDATE\sa\scorrupt\sRTREE\sindex.
-D 2019-01-08T14:28:02.662
+C Performance\simprovement\son\sthe\sinstr()\sfunction,\sespecially\sfor\slarge\nhaystacks.
+D 2019-01-08T15:18:24.588
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in d8b254f8bb81bab43c340d70d17dc3babab40fcc8a348c8255881f780a45fee6
@@ -467,7 +467,7 @@ F src/delete.c 209cd8345b15d1843abeff2d91a6d9c765cf32ff4abcb24411c38fe08e18baab
 F src/expr.c 9ad9c40a83c4218d79de19153b7a8ba7810564a123af7e09281927990bea2964
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c aaf28be73ab21e1e8bf4ac6b94269ebc8c93238d1e6997cb44b527b622e8ae6f
-F src/func.c 7c288b4ce309b5a8b8473514b88e1f8e69a80134509a8c0db8e39c858e367e7f
+F src/func.c 6cf832abbc2815fdb46fee654df32a66ab77deb47bf4cff04a5774dafecd497a
 F src/global.c 8291eee0782b83124de14ec0389ec9fd6ae1873358a6b0d9469fe17a46ad803b
 F src/hash.c a12580e143f10301ed5166ea4964ae2853d3905a511d4e0c44497245c7ce1f7a
 F src/hash.h ab34c5c54a9e9de2e790b24349ba5aab3dbb4fd4
@@ -1797,7 +1797,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 673a7dd698eca05bb2909fa01f962a0667361732a6d0e61cf7780ead4a07c967
-R 8b60ad3cb0e573d17f66ab6027826fe9
+P 63eb803dbc27077007dbee8def659d1523724eb73f1def1cdb68027e5c20843a
+R 174e6d1a2fb646acc0dac426835bced6
 U drh
-Z 9698f42eb061c3571f9cb42a9d8aa284
+Z 637ee479b8367750ae4cc1eec21d49de
diff --git a/manifest.uuid b/manifest.uuid
index 1aa891ede4..f89171316d 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-63eb803dbc27077007dbee8def659d1523724eb73f1def1cdb68027e5c20843a
\ No newline at end of file
+ce51f1a2b6a1789a5876e01cf829e45d84f3851d135a2fa5c44a56f948673a60
\ No newline at end of file
diff --git a/src/func.c b/src/func.c
index 0504a8f026..11598a7adc 100644
--- a/src/func.c
+++ b/src/func.c
@@ -201,6 +201,7 @@ static void instrFunc(
   int typeHaystack, typeNeedle;
   int N = 1;
   int isText;
+  unsigned char firstChar;
 
   UNUSED_PARAMETER(argc);
   typeHaystack = sqlite3_value_type(argv[0]);
@@ -219,7 +220,10 @@ static void instrFunc(
       isText = 1;
     }
     if( zNeedle==0 || (nHaystack && zHaystack==0) ) return;
-    while( nNeedle<=nHaystack && memcmp(zHaystack, zNeedle, nNeedle)!=0 ){
+    firstChar = zNeedle[0];
+    while( nNeedle<=nHaystack
+       && (zHaystack[0]!=firstChar || memcmp(zHaystack, zNeedle, nNeedle)!=0)
+    ){
       N++;
       do{
         nHaystack--;