Author: brj

Description:
Short version: certain pages from an XML dump (I haven't figured out any distinguishing characteristics) fail to import. Removing the call to deadlockLoop in SpecialImport.php fixes the problem.

Background: I'm attempting to migrate a wiki from UseMod wiki to MediaWiki. Luckily, MediaWiki includes a script to dump a UseMod wiki into MediaWiki's import/export format. I used this script, it worked without problems, and I now have a dump.

Now the problem: importing the dump. Running importDump.php with the dump file gives an error, so I split the dump into individual pages in order to try to isolate the problem. About a quarter of the pages imported successfully, the rest failed with the same error:

Warning: pg_query(): Query failed: ERROR: current transaction is aborted, commands ignored until end of transaction block in /mnt/home/brj/public_html/fw/includes/DatabasePostgres.php on line 499
SQL error: ERROR: current transaction is aborted, commands ignored until end of transaction block
Backtrace:
#0 /mnt/home/brj/public_html/fw/includes/LinksUpdate.php(542): DatabasePostgres->fetchObject(false)
#1 /mnt/home/brj/public_html/fw/includes/LinksUpdate.php(91): LinksUpdate->getExistingImages()
#2 /mnt/home/brj/public_html/fw/includes/LinksUpdate.php(77): LinksUpdate->doIncrementalUpdate()
#3 /mnt/home/brj/public_html/fw/includes/Article.php(2297): LinksUpdate->doUpdate()
#4 /mnt/home/brj/public_html/fw/includes/Article.php(2366): Article->editUpdates('''The time spen...', 'link fix', true, 1188199043, '2110', true)
#5 /mnt/home/brj/public_html/fw/includes/SpecialImport.php(366): Article->createUpdates(Object(Revision))
#6 [internal function]: WikiRevision->importOldRevision()
#7 /mnt/home/brj/public_html/fw/includes/Database.php(1861): call_user_func_array(Array, Array)
#8 /mnt/home/brj/public_html/fw/includes/SpecialImport.php(511): Database->deadlockLoop(Array)
#9 [internal function]: WikiImporter->importRevision(Object(WikiRevision))
#10 /mnt/home/brj/public_html/fw/maintenance/importDump.php(58): call_user_func(Array, Object(WikiRevision))
#11 [internal function]: BackupReader->handleRevision(Object(WikiRevision), Object(WikiImporter))
#12 /mnt/home/brj/public_html/fw/includes/SpecialImport.php(762): call_user_func_array(Array, Array)
#13 [internal function]: WikiImporter->out_revision(Resource id #31, 'revision')
#14 /mnt/home/brj/public_html/fw/includes/SpecialImport.php(426): xml_parse(Resource id #31, '<?xml version="...', 0)
#15 /mnt/home/brj/public_html/fw/maintenance/importDump.php(109): WikiImporter->doImport()
#16 /mnt/home/brj/public_html/fw/maintenance/importDump.php(96): BackupReader->importFromHandle(Resource id #30)
#17 /mnt/home/brj/public_html/fw/maintenance/importDump.php(131): BackupReader->importFromStdin()

I dug into SpecialImport.php to figure out why this was happening. Eventually I guessed that deadlockLoop might have been written with some MySQL assumptions, and this hadn't been noticed because importing is relatively rare. Since I'm doing a migration, the site I'm importing to isn't live, so I didn't think deadlocks would be an issue. So, I made the following change:

• SpecialImport.php.orig 2007-04-21 05:13:47.000000000 -0700

+++ SpecialImport.php 2007-08-27 00:55:33.000000000 -0700
@@ -506,8 +506,9 @@

• • @private */ function importRevision( &$revision ) {
• $dbw = wfGetDB( DB_MASTER );
• return $dbw->deadlockLoop( array( &$revision, 'importOldRevision' ) );

+ #$dbw = wfGetDB( DB_MASTER );
+ #return $dbw->deadlockLoop( array( &$revision, 'importOldRevision' ) );
+ return $revision->importOldRevision();

}
 
/**

And then importing worked! I'm sure this isn't the actual fix for the problem, as there was probably a reason for the deadlock avoidance, but there's a bug in there somewhere. I can provide sample pages that succeed and fail, if needed. I believe, though I haven't confirmed for sure, that it is consistent which pages succeed and which fail. The proportion has definitely been the same (1/4 succeed, 3/4 fail, out of about 2000 pages) the times I've tried. Also, when attempting to import the failed pages again, all of them fail.

Version: 1.10.x
Severity: normal