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Refactoring the mmap interface. The controlling pragma is now "mmap_size"

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instead of "mmap_limit".  Also change SQLITE_CONFIG_MMAP_LIMIT and
SQLITE_FCNTL_MMAP_LIMIT to SQLITE_CONFIG_MMAP_SIZE and
SQLITE_FCNTL_MMAP_SIZE, respecctively.  
The default mmap_size is now always 0, meaning that
memory mapped I/O is off by default.  There is a new compile-time option
SQLITE_MAX_MMAP_SIZE that determines a hard upper bound on the mmap_size.
Setting SQLITE_MAX_MMAP_SIZE to zero disables the memory-mapped I/O logic
and causes it to be omitted from the build.  An extra argument is added
to SQLITE_CONFIG_MMAP_SIZE that can optionally lower the SQLITE_MAX_MMAP_SIZE
at start-time. The SQLITE_MAX_MMAP_SIZE is zero for platforms where we 
know that it does not work, meaning that it cannot be turned on by mistake
on those platforms.

FossilOrigin-Name: ea1404a10abd7f68e1f8e0708c8a3199d1f79665
This commit is contained in:
drh
2013-04-15 17:03:42 +00:00
parent a1710cc2ea
commit 9b4c59fa1b
31 changed files with 245 additions and 213 deletions
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6
src/btree.c
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@@ -1876,7 +1876,7 @@ int sqlite3BtreeOpen(
rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
EXTRA_SIZE, flags, vfsFlags, pageReinit);
if( rc==SQLITE_OK ){
sqlite3PagerSetMmapLimit(pBt->pPager, db->mxMmap);
sqlite3PagerSetMmapLimit(pBt->pPager, db->szMmap);
rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
}
if( rc!=SQLITE_OK ){
@@ -2147,11 +2147,11 @@ int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
** Change the limit on the amount of the database file that may be
** memory mapped.
*/
int sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 mxMmap){
int sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 szMmap){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetMmapLimit(pBt->pPager, mxMmap);
sqlite3PagerSetMmapLimit(pBt->pPager, szMmap);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}