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diff --git a/www/c3ref/wal_checkpoint_v2.html b/www/c3ref/wal_checkpoint_v2.html new file mode 100644 index 0000000..bbd2e61 --- /dev/null +++ b/www/c3ref/wal_checkpoint_v2.html @@ -0,0 +1,224 @@ +<!DOCTYPE html> +<html><head> +<meta name="viewport" content="width=device-width, initial-scale=1.0"> +<meta http-equiv="content-type" content="text/html; charset=UTF-8"> +<link href="../sqlite.css" rel="stylesheet"> +<title>Checkpoint a database</title> +<!-- path=../ --> +</head> +<body> +<div class=nosearch> +<a href="../index.html"> +<img class="logo" src="../images/sqlite370_banner.gif" alt="SQLite" border="0"> +</a> +<div><!-- IE hack to prevent disappearing logo --></div> +<div class="tagline desktoponly"> +Small. Fast. 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Status +information is written back into integers pointed to by L and C. +The M parameter must be a valid <a href="../c3ref/c_checkpoint_full.html">checkpoint mode</a>:</p> + +<p><dl> +<dt>SQLITE_CHECKPOINT_PASSIVE<dd> +Checkpoint as many frames as possible without waiting for any database +readers or writers to finish, then sync the database file if all frames +in the log were checkpointed. The <a href="../c3ref/busy_handler.html">busy-handler callback</a> +is never invoked in the SQLITE_CHECKPOINT_PASSIVE mode. +On the other hand, passive mode might leave the checkpoint unfinished +if there are concurrent readers or writers.</p> + +<p><dt>SQLITE_CHECKPOINT_FULL<dd> +This mode blocks (it invokes the +<a href="../c3ref/busy_handler.html">busy-handler callback</a>) until there is no +database writer and all readers are reading from the most recent database +snapshot. It then checkpoints all frames in the log file and syncs the +database file. This mode blocks new database writers while it is pending, +but new database readers are allowed to continue unimpeded.</p> + +<p><dt>SQLITE_CHECKPOINT_RESTART<dd> +This mode works the same way as SQLITE_CHECKPOINT_FULL with the addition +that after checkpointing the log file it blocks (calls the +<a href="../c3ref/busy_handler.html">busy-handler callback</a>) +until all readers are reading from the database file only. This ensures +that the next writer will restart the log file from the beginning. +Like SQLITE_CHECKPOINT_FULL, this mode blocks new +database writer attempts while it is pending, but does not impede readers.</p> + +<p><dt>SQLITE_CHECKPOINT_TRUNCATE<dd> +This mode works the same way as SQLITE_CHECKPOINT_RESTART with the +addition that it also truncates the log file to zero bytes just prior +to a successful return. +</dl></p> + +<p>If pnLog is not NULL, then *pnLog is set to the total number of frames in +the log file or to -1 if the checkpoint could not run because +of an error or because the database is not in <a href="../wal.html">WAL mode</a>. If pnCkpt is not +NULL,then *pnCkpt is set to the total number of checkpointed frames in the +log file (including any that were already checkpointed before the function +was called) or to -1 if the checkpoint could not run due to an error or +because the database is not in WAL mode. Note that upon successful +completion of an SQLITE_CHECKPOINT_TRUNCATE, the log file will have been +truncated to zero bytes and so both *pnLog and *pnCkpt will be set to zero.</p> + +<p>All calls obtain an exclusive "checkpoint" lock on the database file. If +any other process is running a checkpoint operation at the same time, the +lock cannot be obtained and SQLITE_BUSY is returned. Even if there is a +busy-handler configured, it will not be invoked in this case.</p> + +<p>The SQLITE_CHECKPOINT_FULL, RESTART and TRUNCATE modes also obtain the +exclusive "writer" lock on the database file. If the writer lock cannot be +obtained immediately, and a busy-handler is configured, it is invoked and +the writer lock retried until either the busy-handler returns 0 or the lock +is successfully obtained. The busy-handler is also invoked while waiting for +database readers as described above. If the busy-handler returns 0 before +the writer lock is obtained or while waiting for database readers, the +checkpoint operation proceeds from that point in the same way as +SQLITE_CHECKPOINT_PASSIVE - checkpointing as many frames as possible +without blocking any further. SQLITE_BUSY is returned in this case.</p> + +<p>If parameter zDb is NULL or points to a zero length string, then the +specified operation is attempted on all WAL databases <a href="../lang_attach.html">attached</a> to +<a href="../c3ref/sqlite3.html">database connection</a> db. In this case the +values written to output parameters *pnLog and *pnCkpt are undefined. If +an SQLITE_BUSY error is encountered when processing one or more of the +attached WAL databases, the operation is still attempted on any remaining +attached databases and SQLITE_BUSY is returned at the end. If any other +error occurs while processing an attached database, processing is abandoned +and the error code is returned to the caller immediately. If no error +(SQLITE_BUSY or otherwise) is encountered while processing the attached +databases, SQLITE_OK is returned.</p> + +<p>If database zDb is the name of an attached database that is not in WAL +mode, SQLITE_OK is returned and both *pnLog and *pnCkpt set to -1. If +zDb is not NULL (or a zero length string) and is not the name of any +attached database, SQLITE_ERROR is returned to the caller.</p> + +<p>Unless it returns SQLITE_MISUSE, +the sqlite3_wal_checkpoint_v2() interface +sets the error information that is queried by +<a href="../c3ref/errcode.html">sqlite3_errcode()</a> and <a href="../c3ref/errcode.html">sqlite3_errmsg()</a>.</p> + +<p>The <a href="../pragma.html#pragma_wal_checkpoint">PRAGMA wal_checkpoint</a> command can be used to invoke this interface +from SQL. +</p><p>See also lists of + <a href="objlist.html">Objects</a>, + <a href="constlist.html">Constants</a>, and + <a href="funclist.html">Functions</a>.</p> + |