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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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44
src/sqliteInt.h
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@@ -540,13 +540,46 @@ extern const int sqlite3one;
#endif
/*
** Disable MMAP on platforms where it is not supported
** Disable MMAP on platforms where it is known to not work
*/
#if defined(__OpenBSD__) || defined(__QNXNTO__)
# undef SQLITE_DISABLE_MMAP
# define SQLITE_DISABLE_MMAP 1
# undef SQLITE_MAX_MMAP_SIZE
# define SQLITE_MAX_MMAP_SIZE 0
#endif
/*
** Default maximum size of memory used by memory-mapped I/O in the VFS
*/
#ifdef __APPLE__
# include <TargetConditionals.h>
# if TARGET_OS_IPHONE
# undef SQLITE_MAX_MMAP_SIZE
# define SQLITE_MAX_MMAP_SIZE 0
# endif
#endif
#ifndef SQLITE_MAX_MMAP_SIZE
# if defined(__linux__) \
|| defined(_WIN32) \
|| (defined(__APPLE__) && defined(__MACH__)) \
|| defined(__sun)
# define SQLITE_MAX_MMAP_SIZE 2147483648
# else
# define SQLITE_MAX_MMAP_SIZE 0
# endif
#endif
/*
** The default MMAP_SIZE is zero on all platforms. Or, even if a larger
** default MMAP_SIZE is specified at compile-time, make sure that it does
** not exceed the maximum mmap size.
*/
#ifndef SQLITE_DEFAULT_MMAP_SIZE
# define SQLITE_DEFAULT_MMAP_SIZE 0
#endif
#if SQLITE_DEFAULT_MMAP_SIZE>SQLITE_MAX_MMAP_SIZE
# undef SQLITE_DEFAULT_MMAP_SIZE
# define SQLITE_DEFAULT_MMAP_SIZE SQLITE_MAX_MMAP_SIZE
#endif
/*
** An instance of the following structure is used to store the busy-handler
@@ -842,7 +875,7 @@ struct sqlite3 {
int nDb; /* Number of backends currently in use */
int flags; /* Miscellaneous flags. See below */
i64 lastRowid; /* ROWID of most recent insert (see above) */
i64 mxMmap; /* Default mmap_limit setting */
i64 szMmap; /* Default mmap_size setting */
unsigned int openFlags; /* Flags passed to sqlite3_vfs.xOpen() */
int errCode; /* Most recent error code (SQLITE_*) */
int errMask; /* & result codes with this before returning */
@@ -2516,7 +2549,8 @@ struct Sqlite3Config {
void *pHeap; /* Heap storage space */
int nHeap; /* Size of pHeap[] */
int mnReq, mxReq; /* Min and max heap requests sizes */
sqlite3_int64 mxMmap; /* Maximum mmap() space per open file */
sqlite3_int64 szMmap; /* mmap() space per open file */
sqlite3_int64 mxMmap; /* Maximum value for szMmap */
void *pScratch; /* Scratch memory */
int szScratch; /* Size of each scratch buffer */
int nScratch; /* Number of scratch buffers */