From 18657a960e125336f704ea058e25c27bd3900dcb Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 5 May 2024 19:28:19 +0200 Subject: Adding upstream version 3.40.1. Signed-off-by: Daniel Baumann --- www/c3ref/autovacuum_pages.html | 189 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 www/c3ref/autovacuum_pages.html (limited to 'www/c3ref/autovacuum_pages.html') diff --git a/www/c3ref/autovacuum_pages.html b/www/c3ref/autovacuum_pages.html new file mode 100644 index 0000000..cba4622 --- /dev/null +++ b/www/c3ref/autovacuum_pages.html @@ -0,0 +1,189 @@ + + + + + +Autovacuum Compaction Amount Callback + + + +
+ + + +
+
+Small. Fast. Reliable.
Choose any three. +
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+ +
+ +
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+ + + +
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+ + +
+

SQLite C Interface

 +

Autovacuum Compaction Amount Callback

+
+
+int sqlite3_autovacuum_pages(
+  sqlite3 *db,
+  unsigned int(*)(void*,const char*,unsigned int,unsigned int,unsigned int),
+  void*,
+  void(*)(void*)
+);
+
+

+The sqlite3_autovacuum_pages(D,C,P,X) interface registers a callback +function C that is invoked prior to each autovacuum of the database +file. The callback is passed a copy of the generic data pointer (P), +the schema-name of the attached database that is being autovacuumed, +the size of the database file in pages, the number of free pages, +and the number of bytes per page, respectively. The callback should +return the number of free pages that should be removed by the +autovacuum. If the callback returns zero, then no autovacuum happens. +If the value returned is greater than or equal to the number of +free pages, then a complete autovacuum happens.

+ +

If there are multiple ATTACH-ed database files that are being +modified as part of a transaction commit, then the autovacuum pages +callback is invoked separately for each file.

+ +

The callback is not reentrant. The callback function should +not attempt to invoke any other SQLite interface. If it does, bad +things may happen, including segmentation faults and corrupt database +files. The callback function should be a simple function that +does some arithmetic on its input parameters and returns a result.

+ +

The X parameter to sqlite3_autovacuum_pages(D,C,P,X) is an optional +destructor for the P parameter. If X is not NULL, then X(P) is +invoked whenever the database connection closes or when the callback +is overwritten by another invocation of sqlite3_autovacuum_pages().

+ +

There is only one autovacuum pages callback per database connection. +Each call to the sqlite3_autovacuum_pages() interface overrides all +previous invocations for that database connection. If the callback +argument (C) to sqlite3_autovacuum_pages(D,C,P,X) is a NULL pointer, +then the autovacuum steps callback is cancelled. The return value +from sqlite3_autovacuum_pages() is normally SQLITE_OK, but might +be some other error code if something goes wrong. The current +implementation will only return SQLITE_OK or SQLITE_MISUSE, but other +return codes might be added in future releases.

+ +

If no autovacuum pages callback is specified (the usual case) or +a NULL pointer is provided for the callback, +then the default behavior is to vacuum all free pages. So, in other +words, the default behavior is the same as if the callback function +were something like this:

+ +

+    unsigned int demonstration_autovac_pages_callback(
+      void *pClientData,
+      const char *zSchema,
+      unsigned int nDbPage,
+      unsigned int nFreePage,
+      unsigned int nBytePerPage
+    ){
+      return nFreePage;
+    }
+
+

See also lists of + Objects, + Constants, and + Functions.

+ -- cgit v1.2.3