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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>Appendix K. PostgreSQL Limits</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 V1.79.1" /><link rel="prev" href="docguide-style.html" title="J.5. Style Guide" /><link rel="next" href="acronyms.html" title="Appendix L. Acronyms" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Appendix K. <span xmlns="http://www.w3.org/1999/xhtml" class="productname">PostgreSQL</span> Limits</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="docguide-style.html" title="J.5. Style Guide">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="appendixes.html" title="Part VIII. Appendixes">Up</a></td><th width="60%" align="center">Part VIII. Appendixes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="acronyms.html" title="Appendix L. Acronyms">Next</a></td></tr></table><hr></hr></div><div class="appendix" id="LIMITS"><div class="titlepage"><div><div><h2 class="title">Appendix K. <span class="productname">PostgreSQL</span> Limits</h2></div></div></div><p>
- <a class="xref" href="limits.html#LIMITS-TABLE" title="Table K.1. PostgreSQL Limitations">Table K.1</a> describes various hard limits of
- <span class="productname">PostgreSQL</span>. However, practical limits, such as
- performance limitations or available disk space may apply before absolute
- hard limits are reached.
- </p><div class="table" id="LIMITS-TABLE"><p class="title"><strong>Table K.1. <span class="productname">PostgreSQL</span> Limitations</strong></p><div class="table-contents"><table class="table" summary="PostgreSQL Limitations" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Item</th><th>Upper Limit</th><th>Comment</th></tr></thead><tbody><tr><td>database size</td><td>unlimited</td><td> </td></tr><tr><td>number of databases</td><td>4,294,950,911</td><td> </td></tr><tr><td>relations per database</td><td>1,431,650,303</td><td> </td></tr><tr><td>relation size</td><td>32 TB</td><td>with the default <code class="symbol">BLCKSZ</code> of 8192 bytes</td></tr><tr><td>rows per table</td><td>limited by the number of tuples that can fit onto 4,294,967,295 pages</td><td> </td></tr><tr><td>columns per table</td><td>1600</td><td>further limited by tuple size fitting on a single page; see note
- below</td></tr><tr><td>field size</td><td>1 GB</td><td> </td></tr><tr><td>identifier length</td><td>63 bytes</td><td>can be increased by recompiling <span class="productname">PostgreSQL</span></td></tr><tr><td>indexes per table</td><td>unlimited</td><td>constrained by maximum relations per database</td></tr><tr><td>columns per index</td><td>32</td><td>can be increased by recompiling <span class="productname">PostgreSQL</span></td></tr><tr><td>partition keys</td><td>32</td><td>can be increased by recompiling <span class="productname">PostgreSQL</span></td></tr></tbody></table></div></div><br class="table-break" /><p>
- The maximum number of columns for a table is further reduced as the tuple
- being stored must fit in a single 8192-byte heap page. For example,
- excluding the tuple header, a tuple made up of 1600 <code class="type">int</code> columns
- would consume 6400 bytes and could be stored in a heap page, but a tuple of
- 1600 <code class="type">bigint</code> columns would consume 12800 bytes and would
- therefore not fit inside a heap page.
- Variable-length fields of
- types such as <code class="type">text</code>, <code class="type">varchar</code>, and <code class="type">char</code>
- can have their values stored out of line in the table's TOAST table when the
- values are large enough to require it. Only an 18-byte pointer must remain
- inside the tuple in the table's heap. For shorter length variable-length
- fields, either a 4-byte or 1-byte field header is used and the value is
- stored inside the heap tuple.
- </p><p>
- Columns that have been dropped from the table also contribute to the maximum
- column limit. Moreover, although the dropped column values for newly
- created tuples are internally marked as null in the tuple's null bitmap, the
- null bitmap also occupies space.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="docguide-style.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="appendixes.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="acronyms.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">J.5. Style Guide </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix L. Acronyms</td></tr></table></div></body></html>
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