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diff --git a/doc/src/sgml/html/plpgsql-overview.html b/doc/src/sgml/html/plpgsql-overview.html new file mode 100644 index 0000000..80e9251 --- /dev/null +++ b/doc/src/sgml/html/plpgsql-overview.html @@ -0,0 +1,103 @@ +<?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>43.1. Overview</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="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language" /><link rel="next" href="plpgsql-structure.html" title="43.2. Structure of PL/pgSQL" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">43.1. Overview</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 43. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language</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="plpgsql-structure.html" title="43.2. Structure of PL/pgSQL">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPGSQL-OVERVIEW"><div class="titlepage"><div><div><h2 class="title" style="clear: both">43.1. Overview</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="plpgsql-overview.html#PLPGSQL-ADVANTAGES">43.1.1. Advantages of Using <span class="application">PL/pgSQL</span></a></span></dt><dt><span class="sect2"><a href="plpgsql-overview.html#PLPGSQL-ARGS-RESULTS">43.1.2. Supported Argument and Result Data Types</a></span></dt></dl></div><p> + <span class="application">PL/pgSQL</span> is a loadable procedural + language for the <span class="productname">PostgreSQL</span> database + system. The design goals of <span class="application">PL/pgSQL</span> were to create + a loadable procedural language that + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + can be used to create functions, procedures, and triggers, + </p></li><li class="listitem"><p> + adds control structures to the <acronym class="acronym">SQL</acronym> language, + </p></li><li class="listitem"><p> + can perform complex computations, + </p></li><li class="listitem"><p> + inherits all user-defined types, functions, procedures, and operators, + </p></li><li class="listitem"><p> + can be defined to be trusted by the server, + </p></li><li class="listitem"><p> + is easy to use. + </p></li></ul></div><p> + </p><p> + Functions created with <span class="application">PL/pgSQL</span> can be + used anywhere that built-in functions could be used. + For example, it is possible to + create complex conditional computation functions and later use + them to define operators or use them in index expressions. + </p><p> + In <span class="productname">PostgreSQL</span> 9.0 and later, + <span class="application">PL/pgSQL</span> is installed by default. + However it is still a loadable module, so especially security-conscious + administrators could choose to remove it. + </p><div class="sect2" id="PLPGSQL-ADVANTAGES"><div class="titlepage"><div><div><h3 class="title">43.1.1. Advantages of Using <span class="application">PL/pgSQL</span></h3></div></div></div><p> + <acronym class="acronym">SQL</acronym> is the language <span class="productname">PostgreSQL</span> + and most other relational databases use as query language. It's + portable and easy to learn. But every <acronym class="acronym">SQL</acronym> + statement must be executed individually by the database server. + </p><p> + That means that your client application must send each query to + the database server, wait for it to be processed, receive and + process the results, do some computation, then send further + queries to the server. All this incurs interprocess + communication and will also incur network overhead if your client + is on a different machine than the database server. + </p><p> + With <span class="application">PL/pgSQL</span> you can group a block of + computation and a series of queries <span class="emphasis"><em>inside</em></span> + the database server, thus having the power of a procedural + language and the ease of use of SQL, but with considerable + savings of client/server communication overhead. + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> Extra round trips between + client and server are eliminated </p></li><li class="listitem"><p> Intermediate results that the client does not + need do not have to be marshaled or transferred between server + and client </p></li><li class="listitem"><p> Multiple rounds of query + parsing can be avoided </p></li></ul></div><p> This can result in a considerable performance increase as + compared to an application that does not use stored functions. + </p><p> + Also, with <span class="application">PL/pgSQL</span> you can use all + the data types, operators and functions of SQL. + </p></div><div class="sect2" id="PLPGSQL-ARGS-RESULTS"><div class="titlepage"><div><div><h3 class="title">43.1.2. Supported Argument and Result Data Types</h3></div></div></div><p> + Functions written in <span class="application">PL/pgSQL</span> can accept + as arguments any scalar or array data type supported by the server, + and they can return a result of any of these types. They can also + accept or return any composite type (row type) specified by name. + It is also possible to declare a <span class="application">PL/pgSQL</span> + function as accepting <code class="type">record</code>, which means that any + composite type will do as input, or + as returning <code class="type">record</code>, which means that the result + is a row type whose columns are determined by specification in the + calling query, as discussed in <a class="xref" href="queries-table-expressions.html#QUERIES-TABLEFUNCTIONS" title="7.2.1.4. Table Functions">Section 7.2.1.4</a>. + </p><p> + <span class="application">PL/pgSQL</span> functions can be declared to accept a variable + number of arguments by using the <code class="literal">VARIADIC</code> marker. This + works exactly the same way as for SQL functions, as discussed in + <a class="xref" href="xfunc-sql.html#XFUNC-SQL-VARIADIC-FUNCTIONS" title="38.5.6. SQL Functions with Variable Numbers of Arguments">Section 38.5.6</a>. + </p><p> + <span class="application">PL/pgSQL</span> functions can also be declared to + accept and return the polymorphic types described in + <a class="xref" href="extend-type-system.html#EXTEND-TYPES-POLYMORPHIC" title="38.2.5. Polymorphic Types">Section 38.2.5</a>, thus allowing the actual data + types handled by the function to vary from call to call. + Examples appear in <a class="xref" href="plpgsql-declarations.html#PLPGSQL-DECLARATION-PARAMETERS" title="43.3.1. Declaring Function Parameters">Section 43.3.1</a>. + </p><p> + <span class="application">PL/pgSQL</span> functions can also be declared to return + a <span class="quote">“<span class="quote">set</span>”</span> (or table) of any data type that can be returned as + a single instance. Such a function generates its output by executing + <code class="command">RETURN NEXT</code> for each desired element of the result + set, or by using <code class="command">RETURN QUERY</code> to output the result of + evaluating a query. + </p><p> + Finally, a <span class="application">PL/pgSQL</span> function can be declared to return + <code class="type">void</code> if it has no useful return value. (Alternatively, it + could be written as a procedure in that case.) + </p><p> + <span class="application">PL/pgSQL</span> functions can also be declared with output + parameters in place of an explicit specification of the return type. + This does not add any fundamental capability to the language, but + it is often convenient, especially for returning multiple values. + The <code class="literal">RETURNS TABLE</code> notation can also be used in place + of <code class="literal">RETURNS SETOF</code>. + </p><p> + Specific examples appear in + <a class="xref" href="plpgsql-declarations.html#PLPGSQL-DECLARATION-PARAMETERS" title="43.3.1. Declaring Function Parameters">Section 43.3.1</a> and + <a class="xref" href="plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING" title="43.6.1. Returning from a Function">Section 43.6.1</a>. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpgsql-structure.html" title="43.2. Structure of PL/pgSQL">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 43. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language </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"> 43.2. Structure of <span class="application">PL/pgSQL</span></td></tr></table></div></body></html>
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