This part is about extending the server functionality with user-defined functions, data types, triggers, etc. These are advanced topics which should probably be approached only after all the other user documentation aboutPostgreSQL has been understood. Later chapters in this part describe the server-side programming languages available in thePostgreSQL distribution as well as general issues concerning server-side programming languages. It is essential to read at least the earlier sections ofChapter 35 (covering functions) before diving into the material about server-side programming languages.

Table of Contents

35.ExtendingSQL

35.1.How Extensibility Works

35.2.ThePostgreSQL Type System

35.3.User-defined Functions

35.4.Query Language (SQL) Functions

35.5.Function Overloading

35.6.Function Volatility Categories

35.7.Procedural Language Functions

35.8.Internal Functions

35.9.C-Language Functions

35.10.User-defined Aggregates

35.11.User-defined Types

35.12.User-defined Operators

35.13.Operator Optimization Information

35.14.Interfacing Extensions To Indexes

35.15.Packaging Related Objects into an Extension

35.16.Extension Building Infrastructure

36.Triggers

36.1.Overview of Trigger Behavior

36.2.Visibility of Data Changes

36.3.Writing Trigger Functions in C

36.4.A Complete Trigger Example

37.Event Triggers

37.1.Overview of Event Trigger Behavior

37.2.Event Trigger Firing Matrix

37.3.Writing Event Trigger Functions in C

37.4.A Complete Event Trigger Example

38.The Rule System

38.1.The Query Tree

38.2.Views and the Rule System

38.3.Materialized Views

38.4.Rules onINSERT,UPDATE, andDELETE

38.5.Rules and Privileges

38.6.Rules and Command Status

38.7.Rules Versus Triggers

39.Procedural Languages

39.1.Installing Procedural Languages

40.PL/pgSQL -SQL Procedural Language

40.1.Overview

40.2.Structure ofPL/pgSQL

40.3.Declarations

40.4.Expressions

40.5.Basic Statements

40.6.Control Structures

40.7.Cursors

40.8.Errors and Messages

40.9.Trigger Procedures

40.10.PL/pgSQL Under the Hood

40.11.Tips for Developing inPL/pgSQL

40.12.Porting fromOracle PL/SQL

41.PL/Tcl - Tcl Procedural Language

41.1.Overview

41.2.PL/Tcl Functions and Arguments

41.3.Data Values in PL/Tcl

41.4.Global Data in PL/Tcl

41.5.Database Access from PL/Tcl

41.6.Trigger Procedures in PL/Tcl

41.7.Event Trigger Procedures in PL/Tcl

41.8.Modules and theunknown Command

41.9.Tcl Procedure Names

42.PL/Perl - Perl Procedural Language

42.1.PL/Perl Functions and Arguments

42.2.Data Values in PL/Perl

42.3.Built-in Functions

42.4.Global Values in PL/Perl

42.5.Trusted and Untrusted PL/Perl

42.6.PL/Perl Triggers

42.7.PL/Perl Event Triggers

42.8.PL/Perl Under the Hood

43.PL/Python - Python Procedural Language

43.1.Python 2 vs. Python 3

43.2.PL/Python Functions

43.3.Data Values

43.4.Sharing Data

43.5.Anonymous Code Blocks

43.6.Trigger Functions

43.7.Database Access

43.8.Explicit Subtransactions

43.9.Utility Functions

43.10.Environment Variables

44.Server Programming Interface

44.1.Interface Functions

44.2.Interface Support Functions

44.3.Memory Management

44.4.Visibility of Data Changes

44.5.Examples

45.Background Worker Processes

46.Logical Decoding

46.1.Logical Decoding Examples

46.2.Logical Decoding Concepts

46.3.Streaming Replication Protocol Interface

46.4.Logical DecodingSQL Interface

46.5.System Catalogs Related to Logical Decoding

46.6.Logical Decoding Output Plugins

46.7.Logical Decoding Output Writers

46.8.Synchronous Replication Support for Logical Decoding