From: drh <drh@noemail.net>
Date: Fri, 13 May 2016 12:12:38 +0000 (+0000)
Subject: Clarification of the pagerFlushOnCommit() logic.
X-Git-Tag: version-3.13.0~5
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4bf7d21f5647d96ece52fc0a95f01ab5a142a954;p=thirdparty%2Fsqlite.git

Clarification of the pagerFlushOnCommit() logic.

FossilOrigin-Name: 3401d9dcdbec390564574e8d2972c944c204e025
---

diff --git a/manifest b/manifest
index 61125eca3d..12e791556f 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\spager_end_transaction()\sto\sensure\sthat\sa\sROLLBACK\sdoes\snot\sclobber\nunwritten\spages\sin\sa\sTEMP\sfile\spcache.
-D 2016-05-13T11:50:00.812
+C Clarification\sof\sthe\spagerFlushOnCommit()\slogic.
+D 2016-05-13T12:12:38.291
 F Makefile.in 9eda6e1c90d05c199c3ec8a7069b0682ad307657
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc db82b35aef27f412fef14d8534afc022138bcdfd
@@ -364,7 +364,7 @@ F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
 F src/os_unix.c a9443cdab41d7f3cdf0df3a5aab62fd6e1c9b234
 F src/os_win.c 852fc2ff6084296348ed3739c548b2cf32df394e
 F src/os_win.h eb7a47aa17b26b77eb97e4823f20a00b8bda12ca
-F src/pager.c 64f42bd0d20f180f99727ce5a3755a97c9a12700
+F src/pager.c 665c5a4da55952ac144c29d83e7f24393ce80dce
 F src/pager.h 329bdf078a4e0a3b35084534d58625d21fd03681
 F src/parse.y 10eb2f3fb62341291528c7984498054731f9d31e
 F src/pcache.c ad5ce697dc5a734caddb2b1eac83b195da95ddbe
@@ -1488,7 +1488,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 32a62e3bd46cf58586617d3f8b1a971c91df205e
-R 7ea6babb6ca28821d5ebb371842cc2c9
+P 9495d33879221c1821331dc72c61a6a3d182f526
+R 6b2058239dcedcc73d7ba7314be4d002
 U drh
-Z 5e0d604d556f91727b00c6f570867611
+Z 481738e778b68e5e24387a60a8825df4
diff --git a/manifest.uuid b/manifest.uuid
index bed68c74ab..b9dc436b75 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9495d33879221c1821331dc72c61a6a3d182f526
\ No newline at end of file
+3401d9dcdbec390564574e8d2972c944c204e025
\ No newline at end of file
diff --git a/src/pager.c b/src/pager.c
index 095fce5374..0cf2278562 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -1876,20 +1876,24 @@ static int pager_error(Pager *pPager, int rc){
 static int pager_truncate(Pager *pPager, Pgno nPage);
 
 /*
-** The write transaction open on the pager passed as the only argument is
-** being committed. This function returns true if all dirty pages should
-** be flushed to disk, or false otherwise. Pages should be flushed to disk
-** unless one of the following is true:
+** The write transaction open on pPager is being committed (bCommit==1)
+** or rolled back (bCommit==0).
 **
-**   * The db is an in-memory database.
+** Return TRUE if and only if all dirty pages should be flushed to disk.
 **
-**   * The db is a temporary database and the db file has not been opened.
+** Rules:
 **
-**   * The db is a temporary database and the cache contains less than
-**     C/4 dirty pages, where C is the configured cache-size.
+**   *  For non-TEMP databases, always sync to disk.  This is necessary
+**      for transactions to be durable.
+**
+**   *  Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing
+**      file has been created already (via a spill on pagerStress()) and
+**      when the number of dirty pages in memory exceeds 25% of the total
+**      cache size.
 */
-static int pagerFlushOnCommit(Pager *pPager){
+static int pagerFlushOnCommit(Pager *pPager, int bCommit){
   if( pPager->tempFile==0 ) return 1;
+  if( !bCommit ) return 0;
   if( !isOpen(pPager->fd) ) return 0;
   return (sqlite3PCachePercentDirty(pPager->pPCache)>=25);
 }
@@ -2033,7 +2037,7 @@ static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
   pPager->pInJournal = 0;
   pPager->nRec = 0;
   if( rc==SQLITE_OK ){
-    if( !pPager->tempFile || (bCommit && pagerFlushOnCommit(pPager)) ){
+    if( pagerFlushOnCommit(pPager, bCommit) ){
       sqlite3PcacheCleanAll(pPager->pPCache);
     }else{
       sqlite3PcacheClearWritable(pPager->pPCache);
@@ -6206,7 +6210,7 @@ int sqlite3PagerCommitPhaseOne(
 
   assert( MEMDB==0 || pPager->tempFile );
   assert( isOpen(pPager->fd) || pPager->tempFile );
-  if( 0==pagerFlushOnCommit(pPager) ){
+  if( 0==pagerFlushOnCommit(pPager, 1) ){
     /* If this is an in-memory db, or no pages have been written to, or this
     ** function has already been called, it is mostly a no-op.  However, any
     ** backup in progress needs to be restarted.  */