diff options
Diffstat (limited to 'src/sqlite.h.in')
| -rw-r--r-- | src/sqlite.h.in | 37 |
1 files changed, 21 insertions, 16 deletions
diff --git a/src/sqlite.h.in b/src/sqlite.h.in index 961c5169f..928034350 100644 --- a/src/sqlite.h.in +++ b/src/sqlite.h.in @@ -1599,29 +1599,34 @@ struct sqlite3_mem_methods { ** </dd> ** ** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt> -** <dd> ^The SQLITE_CONFIG_PAGECACHE option specifies a static memory buffer +** <dd> ^The SQLITE_CONFIG_PAGECACHE option a memory pool ** that SQLite can use for the database page cache with the default page ** cache implementation. -** This configuration should not be used if an application-define page -** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2] -** configuration option. +** This configuration option is a no-op if an application-define page +** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2]. ** ^There are three arguments to SQLITE_CONFIG_PAGECACHE: A pointer to -** 8-byte aligned -** memory, the size of each page buffer (sz), and the number of pages (N). +** 8-byte aligned memory (pMem), the size of each page cache line (sz), +** and the number of cache lines (N). ** The sz argument should be the size of the largest database page ** (a power of two between 512 and 65536) plus some extra bytes for each ** page header. ^The number of extra bytes needed by the page header -** can be determined using the [SQLITE_CONFIG_PCACHE_HDRSZ] option -** to [sqlite3_config()]. +** can be determined using [SQLITE_CONFIG_PCACHE_HDRSZ]. ** ^It is harmless, apart from the wasted memory, -** for the sz parameter to be larger than necessary. The first -** argument should pointer to an 8-byte aligned block of memory that -** is at least sz*N bytes of memory, otherwise subsequent behavior is -** undefined. -** ^SQLite will use the memory provided by the first argument to satisfy its -** memory needs for the first N pages that it adds to cache. ^If additional -** page cache memory is needed beyond what is provided by this option, then -** SQLite goes to [sqlite3_malloc()] for the additional storage space.</dd> +** for the sz parameter to be larger than necessary. The pMem +** argument must be either a NULL pointer or a pointer to an 8-byte +** aligned block of memory of at least sz*N bytes, otherwise +** subsequent behavior is undefined. +** ^When pMem is not NULL, SQLite will strive to use the memory provided +** to satisfy page cache needs, falling back to [sqlite3_malloc()] if +** a page cache line is larger than sz bytes or if all of the pMem buffer +** is exhausted. +** ^If pMem is NULL and N is non-zero, then each database connection +** does an initial bulk allocation for page cache memory +** from [sqlite3_malloc()] sufficient for N cache lines if N is positive or +** of -1024*N bytes if N is negative, . ^If additional +** page cache memory is needed beyond what is provided by the initial +** allocation, then SQLite goes to [sqlite3_malloc()] separately for each +** additional cache line. </dd> ** ** [[SQLITE_CONFIG_HEAP]] <dt>SQLITE_CONFIG_HEAP</dt> ** <dd> ^The SQLITE_CONFIG_HEAP option specifies a static memory buffer |