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_hash_splitbucket() obtained the base page of the new bucket by calling _hash_getnewbuf(), but it held no exclusive lock that would prevent some other process from calling _hash_getnewbuf() at the same time. This is contrary to _hash_getnewbuf()'s API spec and could in fact cause failures. In practice, we must only call that function while holding write lock on the hash index's metapage. An additional problem was that we'd already modified the metapage's bucket mapping data, meaning that failure to extend the index would leave us with a corrupt index. Fix both issues by moving the _hash_getnewbuf() call to just before we modify the metapage in _hash_expandtable(). Unfortunately there's still a large problem here, which is that we could also incur ENOSPC while trying to get an overflow page for the new bucket. That would leave the index corrupt in a more subtle way, namely that some index tuples that should be in the new bucket might still be in the old one. Fixing that seems substantially more difficult; even preallocating as many pages as we could possibly need wouldn't entirely guarantee that the bucket split would complete successfully. So for today let's just deal with the base case. Per report from Antonin Houska. Back-patch to all active branches. |
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PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: http://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.