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diff --git a/doc/src/sgml/html/catalog-pg-statistic.html b/doc/src/sgml/html/catalog-pg-statistic.html new file mode 100644 index 0000000..b991189 --- /dev/null +++ b/doc/src/sgml/html/catalog-pg-statistic.html @@ -0,0 +1,134 @@ +<?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>53.51. pg_statistic</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="catalog-pg-shseclabel.html" title="53.50. pg_shseclabel" /><link rel="next" href="catalog-pg-statistic-ext.html" title="53.52. pg_statistic_ext" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">53.51. <code class="structname">pg_statistic</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-shseclabel.html" title="53.50. pg_shseclabel">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 53. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 53. System Catalogs</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="catalog-pg-statistic-ext.html" title="53.52. pg_statistic_ext">Next</a></td></tr></table><hr /></div><div class="sect1" id="CATALOG-PG-STATISTIC"><div class="titlepage"><div><div><h2 class="title" style="clear: both">53.51. <code class="structname">pg_statistic</code></h2></div></div></div><a id="id-1.10.4.53.2" class="indexterm"></a><p> + The catalog <code class="structname">pg_statistic</code> stores + statistical data about the contents of the database. Entries are + created by <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a> + and subsequently used by the query planner. Note that all the + statistical data is inherently approximate, even assuming that it + is up-to-date. + </p><p> + Normally there is one entry, with <code class="structfield">stainherit</code> = + <code class="literal">false</code>, for each table column that has been analyzed. + If the table has inheritance children or partitions, a second entry with + <code class="structfield">stainherit</code> = <code class="literal">true</code> is also created. This row + represents the column's statistics over the inheritance tree, i.e., + statistics for the data you'd see with + <code class="literal">SELECT <em class="replaceable"><code>column</code></em> FROM <em class="replaceable"><code>table</code></em>*</code>, + whereas the <code class="structfield">stainherit</code> = <code class="literal">false</code> row represents + the results of + <code class="literal">SELECT <em class="replaceable"><code>column</code></em> FROM ONLY <em class="replaceable"><code>table</code></em></code>. + </p><p> + <code class="structname">pg_statistic</code> also stores statistical data about + the values of index expressions. These are described as if they were + actual data columns; in particular, <code class="structfield">starelid</code> + references the index. No entry is made for an ordinary non-expression + index column, however, since it would be redundant with the entry + for the underlying table column. Currently, entries for index expressions + always have <code class="structfield">stainherit</code> = <code class="literal">false</code>. + </p><p> + Since different kinds of statistics might be appropriate for different + kinds of data, <code class="structname">pg_statistic</code> is designed not + to assume very much about what sort of statistics it stores. Only + extremely general statistics (such as nullness) are given dedicated + columns in <code class="structname">pg_statistic</code>. Everything else + is stored in <span class="quote">“<span class="quote">slots</span>”</span>, which are groups of associated columns + whose content is identified by a code number in one of the slot's columns. + For more information see + <code class="filename">src/include/catalog/pg_statistic.h</code>. + </p><p> + <code class="structname">pg_statistic</code> should not be readable by the + public, since even statistical information about a table's contents + might be considered sensitive. (Example: minimum and maximum values + of a salary column might be quite interesting.) + <a class="link" href="view-pg-stats.html" title="54.27. pg_stats"><code class="structname">pg_stats</code></a> + is a publicly readable view on + <code class="structname">pg_statistic</code> that only exposes information + about those tables that are readable by the current user. + </p><div class="table" id="id-1.10.4.53.8"><p class="title"><strong>Table 53.51. <code class="structname">pg_statistic</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_statistic Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition"> + Column Type + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">starelid</code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-class.html" title="53.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>) + </p> + <p> + The table or index that the described column belongs to + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">staattnum</code> <code class="type">int2</code> + (references <a class="link" href="catalog-pg-attribute.html" title="53.7. pg_attribute"><code class="structname">pg_attribute</code></a>.<code class="structfield">attnum</code>) + </p> + <p> + The number of the described column + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stainherit</code> <code class="type">bool</code> + </p> + <p> + If true, the stats include values from child tables, not just the + values in the specified relation + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stanullfrac</code> <code class="type">float4</code> + </p> + <p> + The fraction of the column's entries that are null + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stawidth</code> <code class="type">int4</code> + </p> + <p> + The average stored width, in bytes, of nonnull entries + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stadistinct</code> <code class="type">float4</code> + </p> + <p> + The number of distinct nonnull data values in the column. + A value greater than zero is the actual number of distinct values. + A value less than zero is the negative of a multiplier for the number + of rows in the table; for example, a column in which about 80% of the + values are nonnull and each nonnull value appears about twice on + average could be represented by <code class="structfield">stadistinct</code> = -0.4. + A zero value means the number of distinct values is unknown. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stakind<em class="replaceable"><code>N</code></em></code> <code class="type">int2</code> + </p> + <p> + A code number indicating the kind of statistics stored in the + <em class="replaceable"><code>N</code></em>th <span class="quote">“<span class="quote">slot</span>”</span> of the + <code class="structname">pg_statistic</code> row. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">staop<em class="replaceable"><code>N</code></em></code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-operator.html" title="53.34. pg_operator"><code class="structname">pg_operator</code></a>.<code class="structfield">oid</code>) + </p> + <p> + An operator used to derive the statistics stored in the + <em class="replaceable"><code>N</code></em>th <span class="quote">“<span class="quote">slot</span>”</span>. For example, a + histogram slot would show the <code class="literal"><</code> operator + that defines the sort order of the data. + Zero if the statistics kind does not require an operator. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stacoll<em class="replaceable"><code>N</code></em></code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-collation.html" title="53.12. pg_collation"><code class="structname">pg_collation</code></a>.<code class="structfield">oid</code>) + </p> + <p> + The collation used to derive the statistics stored in the + <em class="replaceable"><code>N</code></em>th <span class="quote">“<span class="quote">slot</span>”</span>. For example, a + histogram slot for a collatable column would show the collation that + defines the sort order of the data. Zero for noncollatable data. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stanumbers<em class="replaceable"><code>N</code></em></code> <code class="type">float4[]</code> + </p> + <p> + Numerical statistics of the appropriate kind for the + <em class="replaceable"><code>N</code></em>th <span class="quote">“<span class="quote">slot</span>”</span>, or null if the slot + kind does not involve numerical values + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">stavalues<em class="replaceable"><code>N</code></em></code> <code class="type">anyarray</code> + </p> + <p> + Column data values of the appropriate kind for the + <em class="replaceable"><code>N</code></em>th <span class="quote">“<span class="quote">slot</span>”</span>, or null if the slot + kind does not store any data values. Each array's element + values are actually of the specific column's data type, or a related + type such as an array's element type, so there is no way to define + these columns' type more specifically than <code class="type">anyarray</code>. + </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-shseclabel.html" title="53.50. pg_shseclabel">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html" title="Chapter 53. System Catalogs">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-statistic-ext.html" title="53.52. pg_statistic_ext">Next</a></td></tr><tr><td width="40%" align="left" valign="top">53.50. <code class="structname">pg_shseclabel</code> </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"> 53.52. <code class="structname">pg_statistic_ext</code></td></tr></table></div></body></html>
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