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The RecoveryLockLists data structure, which tracks all exclusive locks that the startup process is holding on behalf of transactions being replayed, did not have any provision for avoiding duplicate entries for the same lock. Maybe that was okay when the code was first written. However, modern practice is for checkpoints to write fresh lists of all active exclusive locks into the WAL. Thus, an exclusive lock that survives across multiple checkpoints causes bloat in standbys' startup processes. If there are a lot of such locks this can look like a memory leak, and it's even possible to drive the startup process into a palloc failure from an over-length List. To fix, use a hash table instead of simple lists to track the locks being held. Allowing for dynahash overhead, this requires a little more space per lock than the old way (although it's the same size as what we were allocating prior to c6e0fe1f2). It's probably a shade slower too. However, testing indicates that the penalty is negligible on ordinary workloads, so let's make this change to improve robustness in extreme cases. Patch by me, per report from Dmitriy Kuzmin. No back-patch (for now anyway), since it seems that a significant improvement would only occur in corner cases. Discussion: https://postgr.es/m/CAHLDt=_ts0A7Agn=hCpUh+RCFkxd+G6uuT=kcTfqFtGur0dp=A@mail.gmail.com
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: https://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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.