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The original implementation of TABLESAMPLE modeled the tablesample method API on index access methods, which wasn't a good choice because, without specialized DDL commands, there's no way to build an extension that can implement a TSM. (Raw inserts into system catalogs are not an acceptable thing to do, because we can't undo them during DROP EXTENSION, nor will pg_upgrade behave sanely.) Instead adopt an API more like procedural language handlers or foreign data wrappers, wherein the only SQL-level support object needed is a single handler function identified by having a special return type. This lets us get rid of the supporting catalog altogether, so that no custom DDL support is needed for the feature. Adjust the API so that it can support non-constant tablesample arguments (the original coding assumed we could evaluate the argument expressions at ExecInitSampleScan time, which is undesirable even if it weren't outright unsafe), and discourage sampling methods from looking at invisible tuples. Make sure that the BERNOULLI and SYSTEM methods are genuinely repeatable within and across queries, as required by the SQL standard, and deal more honestly with methods that can't support that requirement. Make a full code-review pass over the tablesample additions, and fix assorted bugs, omissions, infelicities, and cosmetic issues (such as failure to put the added code stanzas in a consistent ordering). Improve EXPLAIN's output of tablesample plans, too. Back-patch to 9.5 so that we don't have to support the original API in production.
281 lines
7.7 KiB
Plaintext
281 lines
7.7 KiB
Plaintext
<!-- doc/src/sgml/postgres.sgml -->
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V4.2//EN" [
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<!ENTITY % version SYSTEM "version.sgml">
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%version;
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<!ENTITY % filelist SYSTEM "filelist.sgml">
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%filelist;
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<!ENTITY reference SYSTEM "reference.sgml">
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]>
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<book id="postgres">
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<title>PostgreSQL &version; Documentation</title>
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<bookinfo>
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<corpauthor>The PostgreSQL Global Development Group</corpauthor>
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<productname>PostgreSQL</productname>
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<productnumber>&version;</productnumber>
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&legal;
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</bookinfo>
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&intro;
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<part id="tutorial">
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<title>Tutorial</title>
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<partintro>
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<para>
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Welcome to the <productname>PostgreSQL</productname> Tutorial. The
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following few chapters are intended to give a simple introduction
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to <productname>PostgreSQL</productname>, relational database
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concepts, and the SQL language to those who are new to any one of
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these aspects. We only assume some general knowledge about how to
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use computers. No particular Unix or programming experience is
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required. This part is mainly intended to give you some hands-on
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experience with important aspects of the
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<productname>PostgreSQL</productname> system. It makes no attempt
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to be a complete or thorough treatment of the topics it covers.
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</para>
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<para>
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After you have worked through this tutorial you might want to move
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on to reading <xref linkend="sql"> to gain a more formal knowledge
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of the SQL language, or <xref linkend="client-interfaces"> for
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information about developing applications for
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<productname>PostgreSQL</productname>. Those who set up and
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manage their own server should also read <xref linkend="admin">.
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</para>
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</partintro>
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&start;
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&query;
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&advanced;
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</part>
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<part id="sql">
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<title>The SQL Language</title>
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<partintro>
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<para>
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This part describes the use of the <acronym>SQL</acronym> language
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in <productname>PostgreSQL</productname>. We start with
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describing the general syntax of <acronym>SQL</acronym>, then
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explain how to create the structures to hold data, how to populate
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the database, and how to query it. The middle part lists the
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available data types and functions for use in
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<acronym>SQL</acronym> commands. The rest treats several
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aspects that are important for tuning a database for optimal
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performance.
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</para>
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<para>
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The information in this part is arranged so that a novice user can
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follow it start to end to gain a full understanding of the topics
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without having to refer forward too many times. The chapters are
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intended to be self-contained, so that advanced users can read the
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chapters individually as they choose. The information in this
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part is presented in a narrative fashion in topical units.
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Readers looking for a complete description of a particular command
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should see <xref linkend="reference">.
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</para>
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<para>
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Readers of this part should know how to connect to a
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<productname>PostgreSQL</> database and issue
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<acronym>SQL</acronym> commands. Readers that are unfamiliar with
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these issues are encouraged to read <xref linkend="tutorial">
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first. <acronym>SQL</acronym> commands are typically entered
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using the <productname>PostgreSQL</> interactive terminal
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<application>psql</application>, but other programs that have
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similar functionality can be used as well.
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</para>
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</partintro>
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&syntax;
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&ddl;
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&dml;
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&queries;
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&datatype;
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&func;
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&typeconv;
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&indices;
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&textsearch;
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&mvcc;
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&perform;
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</part>
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<part id="admin">
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<title>Server Administration</title>
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<partintro>
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<para>
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This part covers topics that are of interest to a
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<productname>PostgreSQL</> database administrator. This includes
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installation of the software, set up and configuration of the
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server, management of users and databases, and maintenance tasks.
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Anyone who runs a <productname>PostgreSQL</> server, even for
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with the topics covered in this part.
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</para>
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<para>
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The information in this part is arranged approximately in the
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order in which a new user should read it. But the chapters are
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self-contained and can be read individually as desired. The
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information in this part is presented in a narrative fashion in
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topical units. Readers looking for a complete description of a
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particular command should see <xref linkend="reference">.
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</para>
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<para>
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The first few chapters are written so they can be understood
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without prerequisite knowledge, so new users who need to set
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up their own server can begin their exploration with this part.
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The rest of this part is about tuning and management; that material
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assumes that the reader is familiar with the general use of
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the <productname>PostgreSQL</> database system. Readers are
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encouraged to look at <xref linkend="tutorial"> and <xref
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linkend="sql"> for additional information.
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</para>
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</partintro>
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&installation;
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&installw;
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&runtime;
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&config;
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&client-auth;
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&user-manag;
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&manage-ag;
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&charset;
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&maintenance;
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&backup;
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&high-availability;
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&recovery-config;
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&monitoring;
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&diskusage;
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&wal;
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®ress;
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</part>
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<part id="client-interfaces">
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<title>Client Interfaces</title>
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<partintro>
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<para>
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This part describes the client programming interfaces distributed
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with <productname>PostgreSQL</>. Each of these chapters can be
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read independently. Note that there are many other programming
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interfaces for client programs that are distributed separately and
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contain their own documentation (<xref linkend="external-projects">
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lists some of the more popular ones). Readers of this part should be
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familiar with using <acronym>SQL</acronym> commands to manipulate
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and query the database (see <xref linkend="sql">) and of course
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with the programming language that the interface uses.
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</para>
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</partintro>
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&libpq;
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&ecpg;
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&infoschema;
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</part>
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<part id="server-programming">
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<title>Server Programming</title>
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<partintro>
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<para>
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This part is about extending the server functionality with
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user-defined functions, data types, triggers, etc. These are
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advanced topics which should probably be approached only after all
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the other user documentation about <productname>PostgreSQL</> has
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been understood. Later chapters in this part describe the server-side
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programming languages available in the
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<productname>PostgreSQL</productname> distribution as well as
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general issues concerning server-side programming languages. It
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is essential to read at least the earlier sections of <xref
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linkend="extend"> (covering functions) before diving into the
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material about server-side programming languages.
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</para>
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</partintro>
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&extend;
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&trigger;
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&event-trigger;
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&rules;
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&xplang;
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&plsql;
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&pltcl;
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&plperl;
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&plpython;
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&spi;
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&bgworker;
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&logicaldecoding;
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&replication-origins;
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</part>
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&reference;
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<part id="internals">
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<title>Internals</title>
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<partintro>
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<para>
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This part contains assorted information that might be of use to
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<productname>PostgreSQL</> developers.
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</para>
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</partintro>
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|
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&arch-dev;
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&catalogs;
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&protocol;
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&sources;
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&nls;
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&plhandler;
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&fdwhandler;
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&tablesample-method;
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&custom-scan;
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&geqo;
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&indexam;
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&gist;
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&spgist;
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&gin;
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&brin;
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&storage;
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&bki;
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&planstats;
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</part>
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<part id="appendixes">
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<title>Appendixes</title>
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|
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&errcodes;
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&features;
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</part>
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&biblio;
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<![%include-index;[&bookindex;]]>
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<![%include-xslt-index;[<index id="bookindex"></index>]]>
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</book>
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