diff options
Diffstat (limited to 'doc/src/sgml/html/catalog-pg-attribute.html')
| -rw-r--r-- | doc/src/sgml/html/catalog-pg-attribute.html | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/doc/src/sgml/html/catalog-pg-attribute.html b/doc/src/sgml/html/catalog-pg-attribute.html new file mode 100644 index 0000000..a574d39 --- /dev/null +++ b/doc/src/sgml/html/catalog-pg-attribute.html @@ -0,0 +1,198 @@ +<?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>51.7. pg_attribute</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="catalog-pg-attrdef.html" title="51.6. pg_attrdef" /><link rel="next" href="catalog-pg-authid.html" title="51.8. pg_authid" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">51.7. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_attribute</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-attrdef.html" title="51.6. pg_attrdef">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 51. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 51. System Catalogs</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="catalog-pg-authid.html" title="51.8. pg_authid">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CATALOG-PG-ATTRIBUTE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">51.7. <code class="structname">pg_attribute</code></h2></div></div></div><a id="id-1.10.4.9.2" class="indexterm"></a><p> + The catalog <code class="structname">pg_attribute</code> stores information about + table columns. There will be exactly one + <code class="structname">pg_attribute</code> row for every column in every + table in the database. (There will also be attribute entries for + indexes, and indeed all objects that have <code class="structname">pg_class</code> + entries.) + </p><p> + The term attribute is equivalent to column and is used for + historical reasons. + </p><div class="table" id="id-1.10.4.9.5"><p class="title"><strong>Table 51.7. <code class="structname">pg_attribute</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_attribute 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">attrelid</code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-class.html" title="51.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>) + </p> + <p> + The table this column belongs to + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attname</code> <code class="type">name</code> + </p> + <p> + The column name + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">atttypid</code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-type.html" title="51.62. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>) + </p> + <p> + The data type of this column + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attstattarget</code> <code class="type">int4</code> + </p> + <p> + <code class="structfield">attstattarget</code> controls the level of detail + of statistics accumulated for this column by + <a class="xref" href="sql-analyze.html" title="ANALYZE"><span class="refentrytitle">ANALYZE</span></a>. + A zero value indicates that no statistics should be collected. + A negative value says to use the system default statistics target. + The exact meaning of positive values is data type-dependent. + For scalar data types, <code class="structfield">attstattarget</code> + is both the target number of <span class="quote">“<span class="quote">most common values</span>”</span> + to collect, and the target number of histogram bins to create. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attlen</code> <code class="type">int2</code> + </p> + <p> + A copy of <code class="literal">pg_type.typlen</code> of this column's + type + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attnum</code> <code class="type">int2</code> + </p> + <p> + The number of the column. Ordinary columns are numbered from 1 + up. System columns, such as <code class="structfield">ctid</code>, + have (arbitrary) negative numbers. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attndims</code> <code class="type">int4</code> + </p> + <p> + Number of dimensions, if the column is an array type; otherwise 0. + (Presently, the number of dimensions of an array is not enforced, + so any nonzero value effectively means <span class="quote">“<span class="quote">it's an array</span>”</span>.) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attcacheoff</code> <code class="type">int4</code> + </p> + <p> + Always -1 in storage, but when loaded into a row descriptor + in memory this might be updated to cache the offset of the attribute + within the row + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">atttypmod</code> <code class="type">int4</code> + </p> + <p> + <code class="structfield">atttypmod</code> records type-specific data + supplied at table creation time (for example, the maximum + length of a <code class="type">varchar</code> column). It is passed to + type-specific input functions and length coercion functions. + The value will generally be -1 for types that do not need <code class="structfield">atttypmod</code>. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attbyval</code> <code class="type">bool</code> + </p> + <p> + A copy of <code class="literal">pg_type.typbyval</code> of this column's type + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attstorage</code> <code class="type">char</code> + </p> + <p> + Normally a copy of <code class="literal">pg_type.typstorage</code> of this + column's type. For TOAST-able data types, this can be altered + after column creation to control storage policy. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attalign</code> <code class="type">char</code> + </p> + <p> + A copy of <code class="literal">pg_type.typalign</code> of this column's type + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attnotnull</code> <code class="type">bool</code> + </p> + <p> + This represents a not-null constraint. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">atthasdef</code> <code class="type">bool</code> + </p> + <p> + This column has a default expression or generation expression, in which + case there will be a corresponding entry in the + <code class="structname">pg_attrdef</code> catalog that actually defines the + expression. (Check <code class="structfield">attgenerated</code> to + determine whether this is a default or a generation expression.) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">atthasmissing</code> <code class="type">bool</code> + </p> + <p> + This column has a value which is used where the column is entirely + missing from the row, as happens when a column is added with a + non-volatile <code class="literal">DEFAULT</code> value after the row is created. + The actual value used is stored in the + <code class="structfield">attmissingval</code> column. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attidentity</code> <code class="type">char</code> + </p> + <p> + If a zero byte (<code class="literal">''</code>), then not an identity column. + Otherwise, <code class="literal">a</code> = generated + always, <code class="literal">d</code> = generated by default. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attgenerated</code> <code class="type">char</code> + </p> + <p> + If a zero byte (<code class="literal">''</code>), then not a generated column. + Otherwise, <code class="literal">s</code> = stored. (Other values might be added + in the future.) + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attisdropped</code> <code class="type">bool</code> + </p> + <p> + This column has been dropped and is no longer valid. A dropped + column is still physically present in the table, but is + ignored by the parser and so cannot be accessed via SQL. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attislocal</code> <code class="type">bool</code> + </p> + <p> + This column is defined locally in the relation. Note that a column can + be locally defined and inherited simultaneously. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attinhcount</code> <code class="type">int4</code> + </p> + <p> + The number of direct ancestors this column has. A column with a + nonzero number of ancestors cannot be dropped nor renamed. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attcollation</code> <code class="type">oid</code> + (references <a class="link" href="catalog-pg-collation.html" title="51.12. pg_collation"><code class="structname">pg_collation</code></a>.<code class="structfield">oid</code>) + </p> + <p> + The defined collation of the column, or zero if the column is + not of a collatable data type. + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attacl</code> <code class="type">aclitem[]</code> + </p> + <p> + Column-level access privileges, if any have been granted specifically + on this column + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attoptions</code> <code class="type">text[]</code> + </p> + <p> + Attribute-level options, as <span class="quote">“<span class="quote">keyword=value</span>”</span> strings + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attfdwoptions</code> <code class="type">text[]</code> + </p> + <p> + Attribute-level foreign data wrapper options, as <span class="quote">“<span class="quote">keyword=value</span>”</span> strings + </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition"> + <code class="structfield">attmissingval</code> <code class="type">anyarray</code> + </p> + <p> + This column has a one element array containing the value used when the + column is entirely missing from the row, as happens when the column is + added with a non-volatile <code class="literal">DEFAULT</code> value after the + row is created. The value is only used when + <code class="structfield">atthasmissing</code> is true. If there is no value + the column is null. + </p></td></tr></tbody></table></div></div><br class="table-break" /><p> + In a dropped column's <code class="structname">pg_attribute</code> entry, + <code class="structfield">atttypid</code> is reset to zero, but + <code class="structfield">attlen</code> and the other fields copied from + <code class="structname">pg_type</code> are still valid. This arrangement is needed + to cope with the situation where the dropped column's data type was + later dropped, and so there is no <code class="structname">pg_type</code> row anymore. + <code class="structfield">attlen</code> and the other fields can be used + to interpret the contents of a row of the table. + </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-attrdef.html" title="51.6. pg_attrdef">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html" title="Chapter 51. System Catalogs">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-authid.html" title="51.8. pg_authid">Next</a></td></tr><tr><td width="40%" align="left" valign="top">51.6. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_attrdef</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 51.8. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_authid</code></td></tr></table></div></body></html>
\ No newline at end of file |