From: drh <drh@noemail.net>
Date: Wed, 10 Aug 2016 15:02:49 +0000 (+0000)
Subject: Tweaks to pcache1TruncateUnsafe() to make it slightly smaller and faster and
X-Git-Tag: version-3.15.0~147
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f5dbe7f8d8486f79f0ee1be6ff16176d14156ac4;p=thirdparty%2Fsqlite.git

Tweaks to pcache1TruncateUnsafe() to make it slightly smaller and faster and
easier to test.

FossilOrigin-Name: 059f4e2efefb7b9deaf539110c19bceaeb10c6ce
---

diff --git a/manifest b/manifest
index 65d4efd170..40aa0f764a 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Rearrange\sthe\scode\sinside\ssqlite3RunParser()\sroutine\sso\sthat\ssqlite3Parser()\nis\sonly\scalled\sfrom\sa\ssingle\splace.\s\sThis\sallows\ssqlite3Parser()\sto\sbe\nin-lined,\swhich\sresults\sin\sa\s0.25%\soverall\sperformance\sgain.
-D 2016-08-10T14:40:00.773
+C Tweaks\sto\spcache1TruncateUnsafe()\sto\smake\sit\sslightly\ssmaller\sand\sfaster\sand\neasier\sto\stest.
+D 2016-08-10T15:02:49.189
 F Makefile.in cfd8fb987cd7a6af046daa87daa146d5aad0e088
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc d66d0395c38571aab3804f8db0fa20707ae4609a
@@ -376,7 +376,7 @@ F src/pager.h 966d2769e76ae347c8a32c4165faf6e6cb64546d
 F src/parse.y 99b676e6fc2f4e331ab93e76b3987cffdbd28efa
 F src/pcache.c 5583c8ade4b05075a60ba953ef471d1c1a9c05df
 F src/pcache.h 2cedcd8407eb23017d92790b112186886e179490
-F src/pcache1.c dc8a6052e5136d6b5e6afe51f37485145646f5ab
+F src/pcache1.c 4bb7a6a5300c67d0b033d25adb509c120c03e812
 F src/pragma.c c8b499756658cb8b82cfdbb5845c22cf11f297aa
 F src/pragma.h 64c78a648751b9f4f297276c4eb7507b14b4628c
 F src/prepare.c 22df6171aec1d86904ed2ad30c2348a5748aa04e
@@ -1510,7 +1510,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 8c2701e70ab2553d7a586ff5fe7afa02d8c63199
-R d55f09ced5a54b7cb7985c5709f82b8d
+P 25d1d02b3ea126ade22b2a72649ae55509aa1777
+R 828a3811914080064b74ae479ed3b60e
 U drh
-Z f780132273cb4e2f41bbf55d6f67764f
+Z 4a1a54abd34521e8d97a121a8de840a3
diff --git a/manifest.uuid b/manifest.uuid
index 806e1635fa..3afecdeb57 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-25d1d02b3ea126ade22b2a72649ae55509aa1777
\ No newline at end of file
+059f4e2efefb7b9deaf539110c19bceaeb10c6ce
\ No newline at end of file
diff --git a/src/pcache1.c b/src/pcache1.c
index 1af1ef5bb7..1b1971a399 100644
--- a/src/pcache1.c
+++ b/src/pcache1.c
@@ -637,19 +637,19 @@ static void pcache1TruncateUnsafe(
   assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
   assert( pCache->iMaxKey >= iLimit );
   assert( pCache->nHash > 0 );
-  if( pCache->iMaxKey - iLimit < pCache->nHash/2 ){
+  if( pCache->iMaxKey - iLimit < pCache->nHash ){
     /* If we are just shaving the last few pages off the end of the
     ** cache, then there is no point in scanning the entire hash table.
     ** Only scan those hash slots that might contain pages that need to
     ** be removed. */
-    iStop = iLimit % pCache->nHash;
-    h = pCache->iMaxKey % pCache->nHash;
+    h = iLimit % pCache->nHash;
+    iStop = pCache->iMaxKey % pCache->nHash;
     TESTONLY( nPage = -10; )  /* Disable the pCache->nPage validity check */
   }else{
     /* This is the general case where many pages are being removed.
     ** It is necessary to scan the entire hash table */
-    iStop = 0;
-    h = pCache->nHash - 1;
+    h = pCache->nHash/2;
+    iStop = h - 1;
   }
   for(;;){
     PgHdr1 **pp;
@@ -668,7 +668,7 @@ static void pcache1TruncateUnsafe(
       }
     }
     if( h==iStop ) break;
-    h = h ? h-1 : pCache->nHash - 1;
+    h = (h+1) % pCache->nHash;
   }
   assert( nPage<0 || pCache->nPage==(unsigned)nPage );
 }