update example code

[wfpl.git] / db.php

diff --git a/db.php b/db.php
index 229fe10..d24d8b6 100644 (file)
--- a/db.php
+++ b/db.php
@@ -64,9 +64,10 @@ function db_connect_now($database = 'auto', $user = 'auto', $pass = 'auto', $hos
                }
        }
 
-       $GLOBALS['wfpl_db_handle'] = mysqli_connect($host, $user, $pass);
+       $GLOBALS['wfpl_db_handle'] = @mysqli_connect($host, $user, $pass);
        if(!$GLOBALS['wfpl_db_handle']) {
-               die('Could not connect to the database: ' . mysqli_error());
+               die('Server error: Database connection failed');
+               # to show username and host: mysqli_connect_error()
        }
 
        mysqli_set_charset($GLOBALS['wfpl_db_handle'], $encoding);
@@ -83,7 +84,7 @@ function _db_connection_needed() {
                return;
        }
        if (isset($GLOBALS['wfpl_db_connect_args'])) {
-               return call_user_func_array(db_connect_now, $GLOBALS['wfpl_db_connect_args']);
+               return call_user_func_array('db_connect_now', $GLOBALS['wfpl_db_connect_args']);
        }
        die('Error: you must call db_connect() or db_auto_connect() first!');
 }
@@ -534,3 +535,73 @@ function db_reposition($table, $row_id, $new_pos, $field = 'ord', $pretty = 'sam
                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');
+       }
+}