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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
| commit | 293913568e6a7a86fd1479e1cff8e2ecb58d6568 (patch) | |
| tree | fc3b469a3ec5ab71b36ea97cc7aaddb838423a0c /doc/src/sgml/html/mvcc-serialization-failure-handling.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.tar.xz postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.zip | |
Adding upstream version 16.2.upstream/16.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
| -rw-r--r-- | doc/src/sgml/html/mvcc-serialization-failure-handling.html | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/doc/src/sgml/html/mvcc-serialization-failure-handling.html b/doc/src/sgml/html/mvcc-serialization-failure-handling.html new file mode 100644 index 0000000..8a0e6e5 --- /dev/null +++ b/doc/src/sgml/html/mvcc-serialization-failure-handling.html @@ -0,0 +1,47 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!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 16.2 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 <a href="#MVCC-SERIALIZATION-FAILURE-HANDLING" class="id_link">#</a></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 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 13.6. Caveats</td></tr></table></div></body></html>
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