-<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.48 2005/11/19 01:50:08 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.49 2006/04/23 03:39:47 momjian Exp $ -->
<sect1 id="arrays">
<title>Arrays</title>
embedded in element values will be backslash-escaped. For numeric
data types it is safe to assume that double quotes will never appear, but
for textual data types one should be prepared to cope with either presence
- or absence of quotes. (This is a change in behavior from pre-7.2
- <productname>PostgreSQL</productname> releases.)
+ or absence of quotes.
</para>
<para>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.79 2006/03/10 19:10:46 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.80 2006/04/23 03:39:48 momjian Exp $ -->
<chapter id="backup">
<title>Backup and Restore</title>
the number after the first dot changes). This does not apply to
different minor releases under the same major release (where the
number after the second dot changes); these always have compatible
- storage formats. For example, releases 7.0.1, 7.1.2, and 7.2 are
- not compatible, whereas 7.1.1 and 7.1.2 are. When you update
+ storage formats. For example, releases 7.2.1, 7.3.2, and 7.4 are
+ not compatible, whereas 7.2.1 and 7.2.2 are. When you update
between compatible versions, you can simply replace the executables
and reuse the data directory on disk. Otherwise you need to back
up your data and restore it on the new server. This has to be done
-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.54 2006/04/18 12:41:15 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.55 2006/04/23 03:39:48 momjian Exp $ -->
<chapter Id="runtime-config">
<title>Server Configuration</title>
<indexterm><primary>inheritance</></>
<listitem>
<para>
- This controls the inheritance semantics, in particular whether
- subtables are included by various commands by default. They were
- not included in versions prior to 7.1. If you need the old
- behavior you can set this variable to <literal>off</>, but in
- the long run you are encouraged to change your applications to
- use the <literal>ONLY</literal> key word to exclude subtables.
- See <xref linkend="ddl-inherit"> for more information about
- inheritance.
+ This controls the inheritance semantics. If turned <literal>off</>,
+ subtables are not included by various commands by default; basically
+ an implied <literal>ONLY</literal> key word. This was added for
+ compatibility with releases prior to 7.1. See
+ <xref linkend="ddl-inherit"> for more information.
</para>
</listitem>
</varlistentry>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.166 2006/03/10 19:10:47 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.167 2006/04/23 03:39:49 momjian Exp $ -->
<chapter id="datatype">
<title id="datatype-title">Data Types</title>
string.
</para>
- <para>
- If one explicitly casts a value to <type>character
- varying(<replaceable>n</>)</type> or
- <type>character(<replaceable>n</>)</type>, then an over-length
- value will be truncated to <replaceable>n</> characters without
- raising an error. (This too is required by the
- <acronym>SQL</acronym> standard.)
- </para>
-
- <note>
- <para>
- Prior to <productname>PostgreSQL</> 7.2, strings that were too long were
- always truncated without raising an error, in either explicit or
- implicit casting contexts.
- </para>
- </note>
+ <para>
+ If one explicitly casts a value to <type>character
+ varying(<replaceable>n</>)</type> or
+ <type>character(<replaceable>n</>)</type>, then an over-length
+ value will be truncated to <replaceable>n</> characters without
+ raising an error. (This too is required by the
+ <acronym>SQL</acronym> standard.)
+ </para>
<para>
The notations <type>varchar(<replaceable>n</>)</type> and
</para>
</note>
- <note>
- <para>
- Prior to <productname>PostgreSQL</> 7.2, <type>bit</type> data
- was always silently truncated or zero-padded on the right, with
- or without an explicit cast. This was changed to comply with the
- <acronym>SQL</acronym> standard.
- </para>
- </note>
-
<para>
Refer to <xref
linkend="sql-syntax-bit-strings"> for information about the syntax
-<!-- $PostgreSQL: pgsql/doc/src/sgml/datetime.sgml,v 2.48 2006/03/10 19:10:47 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/datetime.sgml,v 2.49 2006/04/23 03:39:50 momjian Exp $ -->
<appendix id="datetime-appendix">
<title>Date/Time Support</title>
<tip>
<para>
Gregorian years AD 1-99 may be entered by using 4 digits with leading
- zeros (e.g., <literal>0099</> is AD 99). Previous versions of
- <productname>PostgreSQL</productname> accepted years with three
- digits and with single digits, but as of version 7.0 the rules have
- been tightened up to reduce the possibility of ambiguity.
+ zeros (e.g., <literal>0099</> is AD 99).
</para>
</tip>
</para>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.55 2006/02/18 23:14:45 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.56 2006/04/23 03:39:50 momjian Exp $ -->
<chapter id="ddl">
<title>Data Definition</title>
<note>
<title>Deprecated</title>
<para>
- In previous versions of <productname>PostgreSQL</productname>, the
+ In releases of <productname>PostgreSQL</productname> prior to 7.1, the
default behavior was not to include child tables in queries. This was
- found to be error prone and is also in violation of the SQL
- standard. Under the old syntax, to include the child tables you append
- <literal>*</literal> to the table name. For example:
-<programlisting>
-SELECT * from cities*;
-</programlisting>
- You can still explicitly specify scanning child tables by
- appending <literal>*</literal>, as well as explicitly specify not
- scanning child tables by writing <literal>ONLY</literal>. But
- beginning in version 7.1, the default behavior for an undecorated
- table name is to scan its child tables too, whereas before the
- default was not to do so. To get the old default behavior,
- disable the <xref linkend="guc-sql-inheritance"> configuration
+ found to be error prone and also in violation of the SQL
+ standard. You can get the pre-7.1 behavior by turning off the
+ <xref linkend="guc-sql-inheritance"> configuration
option.
</para>
</note>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.313 2006/03/10 20:15:25 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.314 2006/04/23 03:39:50 momjian Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
the result is given to the full available precision.
</para>
- <note>
- <para>
- Prior to <productname>PostgreSQL</productname> 7.2, the precision
- parameters were unimplemented, and the result was always given
- in integer seconds.
- </para>
- </note>
-
<para>
Some examples:
<screen>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.206 2006/03/10 19:10:48 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.207 2006/04/23 03:39:51 momjian Exp $ -->
<chapter id="libpq">
<title><application>libpq</application> - C Library</title>
<indexterm><primary>libpq-int.h</></>
<application>libpq</application> application programmers should be careful to
maintain the <structname>PGconn</structname> abstraction. Use the accessor
-functions described below to get
-at the contents of <structname>PGconn</structname>. Avoid directly referencing the fields of the
-<structname>PGconn</> structure because they are subject to change in the future.
-(Beginning in <productname>PostgreSQL</productname> release 6.4, the
-definition of the <type>struct</type> behind <structname>PGconn</> is not even provided in <filename>libpq-fe.h</filename>.
-If you have old code that accesses <structname>PGconn</structname> fields directly, you can keep using it
-by including <filename>libpq-int.h</filename> too, but you are encouraged to fix the code
-soon.)
+functions described below to get at the contents of <structname>PGconn</structname>.
+Reference to internal <structname>PGconn</structname> fields using
+<filename>libpq-int.h</> is not recommended because they are subject to change
+in the future.
</para>
</tip>
typedef struct pgNotify {
char *relname; /* notification condition name */
- int be_pid; /* process ID of server process */
+ int be_pid; /* process ID of notifying server process */
char *extra; /* notification parameter */
} PGnotify;
</synopsis>
always point to an empty string.)
</para>
-<note>
-<para>
- In <productname>PostgreSQL</productname> 6.4 and later,
- the <structfield>be_pid</structfield> is that of the notifying server process,
- whereas in earlier versions it was always the <acronym>PID</acronym> of your own server process.
-</para>
-</note>
-
<para>
<xref linkend="libpq-example-2"> gives a sample program that illustrates the use
of asynchronous notification.
</itemizedlist>
</para>
- <para>
- <indexterm><primary>libpq-int.h</></>
- If your codes references the header file
- <filename>libpq-int.h</filename> and you refuse to fix your code to
- not use it, starting in <productname>PostgreSQL</> 7.2, this file will be found in
- <filename><replaceable>includedir</replaceable>/postgresql/internal/libpq-int.h</filename>,
- so you need to add the appropriate <option>-I</option> option to
- your compiler command line.
- </para>
-
</sect1>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.39 2006/03/10 19:10:48 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.40 2006/04/23 03:39:52 momjian Exp $ -->
<chapter id="largeObjects">
<title id="largeObjects-title">Large Objects</title>
values. This is not described here.
</para>
- <sect1 id="lo-history">
- <title>History</title>
+ <sect1 id="lo-intro">
+ <title>Introduction</title>
- <para>
- <productname>POSTGRES 4.2</productname>, the indirect predecessor
- of <productname>PostgreSQL</productname>, supported three standard
- implementations of large objects: as files external to the
- <productname>POSTGRES</productname> server, as external files
- managed by the <productname>POSTGRES</productname> server, and as
- data stored within the <productname>POSTGRES</productname>
- database. This caused considerable confusion among users. As a
- result, only support for large objects as data stored within the
- database is retained in <productname>PostgreSQL</productname>.
- Even though this is slower to access, it provides stricter data
- integrity. For historical reasons, this storage scheme is
- referred to as <firstterm>Inversion large
- objects</firstterm>. (You will see the term Inversion used
- occasionally to mean the same thing as large object.) Since
- <productname>PostgreSQL 7.1</productname>, all large objects are
- placed in one system table called
- <classname>pg_largeobject</classname>.
- </para>
+ <indexterm>
+ <primary>TOAST</primary>
+ <secondary>versus large objects</secondary>
+ </indexterm>
<para>
- <indexterm>
- <primary>TOAST</primary>
- <secondary>versus large objects</secondary>
- </indexterm>
- <productname>PostgreSQL</productname> 7.1 introduced a mechanism
- (nicknamed <quote><acronym>TOAST</acronym></quote>) that allows
- data values to be much larger than single pages. This
- makes the large object facility partially obsolete. One
+ All large objects are placed in a single system table called
+ <classname>pg_largeobject</classname>.
+ <productname>PostgreSQL</productname> also supports a storage system called
+ <quote><acronym>TOAST</acronym></quote> that automatically stores values
+ larger than a single database page into a secondary storage area per table.
+ This makes the large object facility partially obsolete. One
remaining advantage of the large object facility is that it allows values
up to 2 GB in size, whereas <acronym>TOAST</acronym>ed fields can be at
- most 1 GB. Also, large objects can be manipulated piece-by-piece much more
- easily than ordinary data fields, so the practical limits are considerably
- different.
+ most 1 GB. Also, large objects can be randomly modified using a read/write
+ API that is more efficient than performing such operations using
+ <acronym>TOAST</acronym>.
</para>
</sect1>
<title>Implementation Features</title>
<para>
- The large object implementation breaks large
- objects up into <quote>chunks</quote> and stores the chunks in
+ The large object implementation breaks large
+ objects up into <quote>chunks</quote> and stores the chunks in
rows in the database. A B-tree index guarantees fast
searches for the correct chunk number when doing random
access reads and writes.
<productname>PostgreSQL</productname> client interface libraries
provide for accessing large objects. All large object
manipulation using these functions <emphasis>must</emphasis> take
- place within an SQL transaction block. (This requirement is
- strictly enforced as of <productname>PostgreSQL 6.5</>, though it
- has been an implicit requirement in previous versions, resulting
- in misbehavior if ignored.)
+ place within an SQL transaction block.
The <productname>PostgreSQL</productname> large object interface is modeled after
the <acronym>Unix</acronym> file-system interface, with analogues of
<function>open</function>, <function>read</function>,
-<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.54 2006/03/10 19:10:48 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.55 2006/04/23 03:39:52 momjian Exp $ -->
<chapter id="maintenance">
<title>Routine Database Maintenance Tasks</title>
</para>
<para>
- Beginning in <productname>PostgreSQL</productname> 7.2, the standard form
- of <command>VACUUM</> can run in parallel with normal database operations
- (selects, inserts, updates, deletes, but not changes to table definitions).
- Routine vacuuming is therefore not nearly as intrusive as it was in prior
- releases, and it is not as critical to try to schedule it at low-usage
- times of day.
- </para>
-
- <para>
+ The standard form of <command>VACUUM</> can run in parallel with
+ normal database operations (SELECTs, INSERTs, UPDATEs, DELETEs, but not
+ changes to table definitions).
Beginning in <productname>PostgreSQL</productname> 8.0, there are
configuration parameters that can be adjusted to further reduce the
performance impact of background vacuuming. See
It is possible to run <command>ANALYZE</> on specific tables and even
just specific columns of a table, so the flexibility exists to update some
statistics more frequently than others if your application requires it.
- In practice, however, the usefulness of this feature is doubtful.
- Beginning in <productname>PostgreSQL</productname> 7.2,
- <command>ANALYZE</> is a fairly fast operation even on large tables,
- because it uses a statistical random sampling of the rows of a table
- rather than reading every single row. So it's probably much simpler
- to just run it over the whole database every so often.
+ In practice, however, it is usually best to just analyze the entire database
+ because it is a fast operation. It uses a statistical random sampling of
+ the rows of a table rather than reading every single row.
</para>
<tip>
transactions that were in the past appear to be in the future — which
means their outputs become invisible. In short, catastrophic data loss.
(Actually the data is still there, but that's cold comfort if you can't
- get at it.)
- </para>
-
- <para>
- Prior to <productname>PostgreSQL</productname> 7.2, the only defense
- against XID wraparound was to re-<command>initdb</> at least every 4
- billion transactions. This of course was not very satisfactory for
- high-traffic sites, so a better solution has been devised. The new
- approach allows a server to remain up indefinitely, without
- <command>initdb</> or any sort of restart. The price is this
- maintenance requirement: <emphasis>every table in the database must
- be vacuumed at least once every billion transactions</emphasis>.
+ get at it.) To avoid this, it is <emphasis>necessary to vacuum every table
+ in every database at least once every billion transactions</emphasis>.
</para>
<para>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/mvcc.sgml,v 2.55 2006/03/10 19:10:48 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/mvcc.sgml,v 2.56 2006/04/23 03:39:52 momjian Exp $ -->
<chapter id="mvcc">
<title>Concurrency Control</title>
TABLE</command> locks the whole table.) This should be taken into
account when porting applications to
<productname>PostgreSQL</productname> from other environments.
- (Before version 6.5 <productname>PostgreSQL</productname> used
- read locks, and so this above consideration is also relevant when
- upgrading from <productname>PostgreSQL</productname> versions
- prior to 6.5.)
</para>
<para>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/rules.sgml,v 1.44 2005/10/22 14:44:35 alvherre Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/rules.sgml,v 1.45 2006/04/23 03:39:52 momjian Exp $ -->
<chapter id="rules">
<title>The Rule System</title>
<para>
Another situation is cases on <command>UPDATE</command> where it depends on the
change of an attribute if an action should be performed or
- not. In <productname>PostgreSQL</productname> version 6.4, the
- attribute specification for rule events is disabled (it will have
- its comeback latest in 6.5, maybe earlier
- - stay tuned). So for now the only way to
+ not. The only way to
create a rule as in the shoelace_log example is to do it with
a rule qualification. That results in an extra query that is
performed always, even if the attribute of interest cannot
-<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.9 2006/03/10 19:10:49 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.10 2006/04/23 03:39:52 momjian Exp $ -->
<chapter id="storage">
</para>
<para>
-Since <productname>PostgreSQL</productname> uses a fixed page size (commonly
-8Kb), and does not allow tuples to span multiple pages, it's not possible to
-store very large field values directly. Before <productname>PostgreSQL</> 7.1
-there was a hard limit of just under one page on the total amount of data that
-could be put into a table row. In release 7.1 and later, this limit is
-overcome by allowing large field values to be compressed and/or broken up into
-multiple physical rows. This happens transparently to the user, with only
-small impact on most of the backend code. The technique is affectionately
-known as <acronym>TOAST</> (or <quote>the best thing since sliced bread</>).
+<productname>PostgreSQL</productname> uses a fixed page size (commonly
+8Kb), and does not allow tuples to span multiple pages. Therefore, it is
+not possible to store very large field values directly. To overcome
+this limitation, large field values are compressed and/or broken up into
+multiple physical rows. This happens transparently to the user, with only
+small impact on most of the backend code. The technique is affectionately
+known as <acronym>TOAST</> (or <quote>the best thing since sliced bread</>).
</para>
<para>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.111 2006/03/10 19:10:49 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.112 2006/04/23 03:39:52 momjian Exp $ -->
<sect1 id="xfunc">
<title>User-Defined Functions</title>
command <literal>pg_config --pkglibdir</literal>.
</para>
- <para>
- Before <productname>PostgreSQL</productname> release 7.2, only
- exact absolute paths to object files could be specified in
- <command>CREATE FUNCTION</>. This approach is now deprecated
- since it makes the function definition unnecessarily unportable.
- It's best to specify just the shared library name with no path nor
- extension, and let the search mechanism provide that information
- instead.
- </para>
</sect2>
<sect2 id="xfunc-c-basetype">
--includedir-server</literal><indexterm><primary>pg_config</><secondary>with user-defined C functions</></>
to find out where the <productname>PostgreSQL</> server header
files are installed on your system (or the system that your
- users will be running on). This option is new with
- <productname>PostgreSQL</> 7.2. For
- <productname>PostgreSQL</> 7.1 you should use the option
- <option>--includedir</option>. (<command>pg_config</command>
- will exit with a non-zero status if it encounters an unknown
- option.) For releases prior to 7.1 you will have to guess,
- but since that was before the current calling conventions were
- introduced, it is unlikely that you want to support those
- releases.
+ users will be running on).
</para>
</listitem>
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