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Revert to allowing a cache spill during writes of multiple pages within a

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single sector as long as the spill does not require a journal sync and a
new journal header.

FossilOrigin-Name: 7d83fbae9802a56b2121d0775de54fccd743d971
This commit is contained in:
drh
2010-06-24 18:36:33 +00:00
parent cfa800cb36
commit 314f30db22
3 changed files with 45 additions and 27 deletions
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46
src/pager.c
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@@ -305,13 +305,15 @@ struct PagerSavepoint {
** master journal name is only written to the journal file the first
** time CommitPhaseOne() is called.
**
** doNotSpill
** doNotSpill, doNotSyncSpill
**
** When enabled, cache spills are prohibited and the journal file cannot
** be synced. This variable is set and cleared by sqlite3PagerWrite()
** in order to prevent a journal sync from happening in between the
** journalling of two pages on the same sector. It is also set to prevent
** pagerStress() from trying to use the journal during a rollback.
** When enabled, cache spills are prohibited. The doNotSpill variable
** inhibits all cache spill and doNotSyncSpill inhibits those spills that
** would require a journal sync. The doNotSyncSpill is set and cleared
** by sqlite3PagerWrite() in order to prevent a journal sync from happening
** in between the journalling of two pages on the same sector. The
** doNotSpill value set to prevent pagerStress() from trying to use
** the journal during a rollback.
**
** needSync
**
@@ -356,6 +358,7 @@ struct Pager {
u8 changeCountDone; /* Set after incrementing the change-counter */
u8 setMaster; /* True if a m-j name has been written to jrnl */
u8 doNotSpill; /* Do not spill the cache when non-zero */
u8 doNotSyncSpill; /* Do not do a spill that requires jrnl sync */
u8 dbSizeValid; /* Set when dbSize is correct */
u8 subjInMemory; /* True to use in-memory sub-journals */
Pgno dbSize; /* Number of pages in the database */
@@ -3518,15 +3521,19 @@ static int pagerStress(void *p, PgHdr *pPg){
assert( pPg->pPager==pPager );
assert( pPg->flags&PGHDR_DIRTY );
/* The doNotSpill flag is set during times when writing to the journal
** is disallowed: (1) during calls to sqlite3PagerWrite() while it
** is journalling a set of two or more database pages that are stored
** on the same disk sector, and (2) while performing a rollback.
/* The doNotSyncSpill flag is set during times when doing a sync of
** journal (and adding a new header) is not allowed. This occurs
** during calls to sqlite3PagerWrite() while trying to journal multiple
** pages belonging to the same sector.
**
** Similarly, if the pager has already entered the error state, do not
** try to write the contents of pPg to disk.
** The doNotSpill flag inhibits all cache spilling regardless of whether
** or not a sync is required. This is set during a rollback.
**
** Spilling is also inhibited when in an error state.
*/
if( pPager->errCode || pPager->doNotSpill ){
if( pPager->errCode ) return SQLITE_OK;
if( pPager->doNotSpill ) return SQLITE_OK;
if( pPager->doNotSyncSpill && (pPg->flags & PGHDR_NEED_SYNC)!=0 ){
return SQLITE_OK;
}
@@ -4834,12 +4841,13 @@ int sqlite3PagerWrite(DbPage *pDbPage){
int ii; /* Loop counter */
int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */
/* Set the doNotSpill flag to 1. This is because we cannot allow a journal
** header to be written between the pages journaled by this function.
/* Set the doNotSyncSpill flag to 1. This is because we cannot allow
** a journal header to be written between the pages journaled by
** this function.
*/
assert( !MEMDB );
assert( pPager->doNotSpill==0 );
pPager->doNotSpill++;
assert( pPager->doNotSyncSpill==0 );
pPager->doNotSyncSpill++;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
@@ -4901,8 +4909,8 @@ int sqlite3PagerWrite(DbPage *pDbPage){
assert(pPager->needSync);
}
assert( pPager->doNotSpill==1 );
pPager->doNotSpill--;
assert( pPager->doNotSyncSpill==1 );
pPager->doNotSyncSpill--;
}else{
rc = pager_write(pDbPage);
}