return $prev_ord + round(($next_ord - $prev_ord) / 2);
}
}
+
+# Call this to upgrade your database (using upgrade functions you define.)
+#
+# You can call this from config.php right after db_connect() to make sure the
+# database is up to date.
+#
+# When you want to update your schema, define a new function named
+# db_upgrade_to_X() where X is the next integer (start at 1).
+#
+# If there are any page views while your upgrade function is running, they will
+# stall until the upgrade function completes. This is often better than running
+# while the databse is in a transitional state, and is way way better than
+# running the upgrade function multiple times concurrently.
+#
+# Efficiency: this function is designed to be lean enough that you'd run it on
+# every page load, so you never forget to upgrade your schema after uploading
+# code changes. If your schema is up to date, this will only execute one
+# database query, and that query loads the persistent data store (used by
+# persistent_get()), so if you use that, you'll need that query to happen
+# anyway (giving this function a zero-query overhead).
+
+function db_upgrade() {
+ if (isset($GLOBALS['wfpl_persistent'])) {
+ $version = persistent_get('wfpl_db_version');
+ } else {
+ # custom version of persistent_init() that creates the table if needed
+ # instead of dying
+ $GLOBALS['wfpl_persistent'] = array();
+ _db_connection_needed();
+ $result = mysqli_query($GLOBALS['wfpl_db_handle'], 'select k,v from wfpl_persistent');
+ if ($result) {
+ while($row = mysqli_fetch_assoc($result)) {
+ $GLOBALS['wfpl_persistent'][$row['k']] = json_decode($row['v'], true);
+ } unset($row);
+ if (isset($GLOBALS['wfpl_persistent']['wfpl_db_version'])) {
+ $version = $GLOBALS['wfpl_persistent']['wfpl_db_version'];
+ } else {
+ $version = -1;
+ }
+ } else {
+ db_send_query('create table if not exists wfpl_persistent (k varchar(30) binary not null default "", v mediumblob, primary key (k)) CHARSET=utf8;');
+ $version = -1;
+ }
+ }
+
+ if ($version === -1) {
+ db_send_query('create table if not exists wfpl_mutexes (id int unique auto_increment, name varchar(30) binary, expires int(11)) CHARSET=utf8;');
+ $version = 0;
+ # don't save version now in case another thread is doing this too
+ }
+ $next = $version + 1;
+ if (function_exists("db_upgrade_to_$next")) {
+ require_once(__DIR__.'/'.'persistent.php');
+ require_once(__DIR__.'/'.'mutex.php');
+ mutex_lock('wfpl_db_upgrade', 20);
+ # check version again, in case another thread upgraded the database
+ # while we waited for a lock just now
+ persistent_invalidate_cache();
+ $version = persistent_get('wfpl_db_version');
+ if ($version === null) {
+ $version = 0;
+ }
+
+ for ($next = $version + 1; function_exists("db_upgrade_to_$next"); ++$next) {
+ call_user_func("db_upgrade_to_$next");
+ persistent_set('wfpl_db_version', $next);
+ }
+ mutex_unlock('wfpl_db_upgrade');
+ }
+}
--- /dev/null
+<?php
+
+function mutex_lock ($name, $duration) {
+ while (true) {
+ $now = time();
+ $deleted_obsoletes = false;
+ db_insert('wfpl_mutexes', 'name,expires', $name, $now + $duration);
+ $id = db_auto_id();
+ $rows = db_get_assocs('wfpl_mutexes', 'id,name,expires', 'order by id');
+ $first_match = true;
+ foreach ($rows as $row) {
+ if ($row['expires'] < $now) {
+ if (!$deleted_obsoletes) {
+ db_delete('wfpl_mutexes', 'where expires < %i', $now);
+ $deleted_obsoletes = true;
+ }
+ } elseif ($row['name'] === $name) {
+ if ($row['id'] == $id) {
+ return $id;
+ } else {
+ break;
+ }
+ }
+ }
+ # not first
+ db_delete('wfpl_mutexes', 'where id=%i', $id);
+ sleep(1);
+ }
+}
+
+function mutex_unlock ($id) {
+ db_delete('wfpl_mutexes', 'where id=%i', $id);
+}
# 1.0 Universal public domain dedication, which can be found at
# http://creativecommons.org/publicdomain/zero/1.0/
-# a simple, persistent, key/value store optimized for many reads
+# a simple, persistent, key/value store optimized for many reads and small data
#
# call persistent_{get,set,clear}
# for internal use
+# IF YOU CHANGE THIS: change the version in db_upgrade() too
function persistent_init() {
if (isset($GLOBALS['wfpl_persistent'])) {
return;
}
$GLOBALS['wfpl_persistent'] = array();
- $rows = db_get_rows('persistent', 'k,v');
+ $rows = db_get_assocs('wfpl_persistent', 'k,v');
foreach ($rows as &$row) {
- $GLOBALS['wfpl_persistent'][$row[0]] = json_decode($row[1], true);
+ $GLOBALS['wfpl_persistent'][$row['k']] = json_decode($row['v'], true);
} unset($row);
}
if ($GLOBALS['wfpl_persistent'][$k] === $v) {
return;
}
- db_update('persistent', 'v', json_encode($v), 'where k=%"', $k);
- } else {
- db_insert('persistent', 'k,v', $k, json_encode($v));
}
+ db_replace('wfpl_persistent', 'k,v', $k, json_encode($v));
$GLOBALS['wfpl_persistent'][$k] = $v;
}
function persistent_clear($k) {
unset($GLOBALS['wfpl_persistent'][$k]);
}
}
+
+function persistent_invalidate_cache() {
+ if (isset($GLOBALS['wfpl_persistent'])) {
+ unset($GLOBALS['wfpl_persistent']);
+ }
+ return;
+}
+