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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:17:33 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:17:33 +0000
commit5e45211a64149b3c659b90ff2de6fa982a5a93ed (patch)
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downloadpostgresql-15-5e45211a64149b3c659b90ff2de6fa982a5a93ed.tar.xz
postgresql-15-5e45211a64149b3c659b90ff2de6fa982a5a93ed.zip
Adding upstream version 15.5.upstream/15.5
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>13.5. Serialization Failure Handling</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="applevel-consistency.html" title="13.4. Data Consistency Checks at the Application Level" /><link rel="next" href="mvcc-caveats.html" title="13.6. Caveats" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">13.5. Serialization Failure Handling</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="applevel-consistency.html" title="13.4. Data Consistency Checks at the Application Level">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="mvcc.html" title="Chapter 13. Concurrency Control">Up</a></td><th width="60%" align="center">Chapter 13. Concurrency Control</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="mvcc-caveats.html" title="13.6. Caveats">Next</a></td></tr></table><hr /></div><div class="sect1" id="MVCC-SERIALIZATION-FAILURE-HANDLING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">13.5. Serialization Failure Handling</h2></div></div></div><a id="id-1.5.12.8.2" class="indexterm"></a><a id="id-1.5.12.8.3" class="indexterm"></a><p>
+ Both Repeatable Read and Serializable isolation levels can produce
+ errors that are designed to prevent serialization anomalies. As
+ previously stated, applications using these levels must be prepared to
+ retry transactions that fail due to serialization errors. Such an
+ error's message text will vary according to the precise circumstances,
+ but it will always have the SQLSTATE code <code class="literal">40001</code>
+ (<code class="literal">serialization_failure</code>).
+ </p><p>
+ It may also be advisable to retry deadlock failures.
+ These have the SQLSTATE code <code class="literal">40P01</code>
+ (<code class="literal">deadlock_detected</code>).
+ </p><p>
+ In some cases it is also appropriate to retry unique-key failures,
+ which have SQLSTATE code <code class="literal">23505</code>
+ (<code class="literal">unique_violation</code>), and exclusion constraint
+ failures, which have SQLSTATE code <code class="literal">23P01</code>
+ (<code class="literal">exclusion_violation</code>). For example, if the
+ application selects a new value for a primary key column after
+ inspecting the currently stored keys, it could get a unique-key
+ failure because another application instance selected the same new key
+ concurrently. This is effectively a serialization failure, but the
+ server will not detect it as such because it cannot <span class="quote">“<span class="quote">see</span>”</span>
+ the connection between the inserted value and the previous reads.
+ There are also some corner cases in which the server will issue a
+ unique-key or exclusion constraint error even though in principle it
+ has enough information to determine that a serialization problem
+ is the underlying cause. While it's recommendable to just
+ retry <code class="literal">serialization_failure</code> errors unconditionally,
+ more care is needed when retrying these other error codes, since they
+ might represent persistent error conditions rather than transient
+ failures.
+ </p><p>
+ It is important to retry the complete transaction, including all logic
+ that decides which SQL to issue and/or which values to use.
+ Therefore, <span class="productname">PostgreSQL</span> does not offer an
+ automatic retry facility, since it cannot do so with any guarantee of
+ correctness.
+ </p><p>
+ Transaction retry does not guarantee that the retried transaction will
+ complete; multiple retries may be needed. In cases with very high
+ contention, it is possible that completion of a transaction may take
+ many attempts. In cases involving a conflicting prepared transaction,
+ it may not be possible to make progress until the prepared transaction
+ commits or rolls back.
+ </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="applevel-consistency.html" title="13.4. Data Consistency Checks at the Application Level">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="mvcc.html" title="Chapter 13. Concurrency Control">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="mvcc-caveats.html" title="13.6. Caveats">Next</a></td></tr><tr><td width="40%" align="left" valign="top">13.4. Data Consistency Checks at the Application Level </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 13.6. Caveats</td></tr></table></div></body></html> \ No newline at end of file