A <command>DROP</command> of the referenced object will result in

automatically dropping the dependent object

whether <literal>CASCADE</literal> is specified or not. If the

dependent objectis reacheddue to a dependency on some other object,

thedrop is converted to a drop of the referenced object, so

that <literal>NORMAL</literal> and <literal>AUTO</literal>

dependent objecthas to be droppeddue to a dependency on some other

object being removed, itsdrop is converted to a drop of the referenced

object, sothat <literal>NORMAL</literal> and <literal>AUTO</literal>

dependencies of the dependent object behave much like they were

dependencies of the referenced object.

Example: a view's <literal>ON SELECT</literal> rule is made

<para>

<structname>pg_stats_ext</structname> is also designed to present the

information in a more readable format than the underlyingcatalog

information in a more readable format than the underlyingcatalogs

&mdash; at the cost that its schema must be extended whenever new types

of extended statistics are added to <structname>pg_statistic_ext</structname>.

</para>

<entry><structfield>attnames</structfield></entry>

<entry><type>name[]</type></entry>

<entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attname</literal></entry>

<entry>Names of thecolumn the extended statistics is defined on</entry>

<entry>Names of thecolumns the extended statistics is defined on</entry>

</row>

<row>

<entry><structfield>n_distinct</structfield></entry>

<entry><type>pg_ndistinct</type></entry>

<entry></entry>

<entry>N-distinct counts for combinations ofcolumns. If greater than

zero, the estimated number of distinct values in the combination. If

less than zero, the negative of the number of distinct values divided

<entry>N-distinct counts for combinations ofcolumn values. If greater

thanzero, the estimated number of distinct values in the combination.

Ifless than zero, the negative of the number of distinct values divided

by the number of rows.

(The negated form is used when <command>ANALYZE</command> believes that

the number of distinct values is likely to increase as the table grows;

<entry><type>anyarray</type></entry>

<entry></entry>

<entry>

A list of the most common combinations in the columns. (Null if

novalues seem to be more common than any others.)

A list of the most common combinationsof valuesin the columns.

(Null ifnocombinations seem to be more common than any others.)

</entry>

</row>

</para>

<para>

Note that the only supported <xref linkend="auth-methods"/> for use

Note that the only supported

<link linkend="auth-methods">authentication methods</link> for use

with <acronym>GSSAPI</acronym> encryption

are <literal>gss</literal>, <literal>reject</literal>,

and <literal>trust</literal>.

<listitem>

<para>

Use GSSAPI to authenticate the user. This is only

available for TCP/IP connections. See <xref

available for TCP/IP connections. See <xref

linkend="gssapi-auth"/> for details. It can be used in conjunction

with GSSAPI encryption.

</para>

<literal>verify-full</literal> additionally enforces that the

<literal>cn</literal> (Common Name) in the certificate matches

the username or an applicable mapping.

This behavior is similar to the cert authentication method

(see <xref linkend="auth-cert"/>) but enables pairing

This behavior is similar to the<literal>cert</literal> authentication

method(see <xref linkend="auth-cert"/>) but enables pairing

the verification of client certificates with any authentication

method that supports <literal>hostssl</literal> entries.

</para>

</para>

<para>

To start the server in standby mode create file called

To start the server in standby mode, create a file called

<filename>standby.signal</filename><indexterm><primary>standby.signal</primary></indexterm>

in the data directory. The server will enter recovery and will not stop

recovery when the end of archived WAL is reached, but will keep trying to

continue recovery by connecting to the sending server as specified by the

<varname>primary_conninfo</varname> setting and/or by fetching new WAL

segments using <varname>restore_command</varname>. In this mode, youmay

segments using <varname>restore_command</varname>. In this mode, youcan

use parameters in both <xref

linkend="runtime-config-wal-archive-recovery"/> and <xref

linkend="runtime-config-replication-standby"/> sections. Parameters from

linkend="runtime-config-replication-standby"/>. Parameters from

<xref linkend="runtime-config-wal-recovery-target"/> will not be used.

</para>

<para>

To start the server in targeted recovery create a file called

To start the server in targeted recoverymode,create a file called

<filename>recovery.signal</filename><indexterm><primary>recovery.signal</primary></indexterm>

in the data directory. If both <filename>standby.signal</filename> and

<filename>recovery.signal</filename> files are created, standby mode

takes precedence. Targeted recovery modewill endwhenend ofarchived

WAL is reached, or when <varname>recovery_target</varname> is reached.

In this mode youmay use parameters from both <xref

takes precedence. Targeted recovery modeendswhenthearchived WAL is

fully replayed, or when <varname>recovery_target</varname> is reached.

In this mode, youcan use parameters from both <xref

linkend="runtime-config-wal-archive-recovery"/> and <xref

linkend="runtime-config-wal-recovery-target"/> sections. Parameters from <xref

linkend="runtime-config-wal-recovery-target"/>. Parameters from <xref

linkend="runtime-config-replication-standby"/> will not be used.

</para>

given decimal precision. The precision used is the standard number of

digits for the type (<literal>FLT_DIG</literal>

or <literal>DBL_DIG</literal> as appropriate) reduced according to the

value of this parameter. (For example, specifying -1 will cause float4

values to be output rounded to 5 significant digits, and float8 values

value of this parameter. (For example, specifying -1 will cause

<type>float4</type> values to be output rounded to 5 significant

digits, and <type>float8</type> values

rounded to 14 digits.) This format is slower and does not preserve all

the bits of the binary float value, but may be more human-readable.

</para>

</term>

<listitem>

<para>

Reports the name of the SSL library that this PostgreSQL server was

built with (even if SSL is not currently configured or in use on this

instance), for example <literal>OpenSSL</literal>,oran empty string

if none.

Reports the name of the SSL library that this

<productname>PostgreSQL</productname> server wasbuilt with (even if

SSL is not currently configuredorin use on this instance), for

example <literal>OpenSSL</literal>, or an empty stringif none.

</para>

</listitem>

</varlistentry>

</para>

<para>

The third option is to declare asql identifier linked to

The third option is to declare aSQL identifier linked to

the connection, for example:

<programlisting>

EXEC SQL AT <replaceable>connection-name</replaceable> DECLARE <replaceable>statement-name</replaceable> STATEMENT;

EXEC SQL PREPARE <replaceable>statement-name</replaceable> FROM :<replaceable>dyn-string</replaceable>;

</programlisting>

Once you link asql identifier to a connection,youexecute a dynamic SQL

withoutAT clause.

Once you link aSQL identifier to a connection, execute dynamic SQL

statements using this identifierwithoutthe <literal>AT</literal> clause.

</para>

</sect2>

<title id="ecpg-type-bytea">bytea</title>

<para>

The handling of the <type>bytea</type> type isalsosimilar to

the <type>VARCHAR</type>. The definition on an array of type

The handling of the <type>bytea</type> type is similar to

that of <type>VARCHAR</type>. The definition on an array of type

<type>bytea</type> is converted into a named struct for every

variable. A declaration like:

<programlisting>

struct bytea_var { int len; char arr[180]; } var;

</programlisting>

The member <structfield>arr</structfield> hosts binary format

data. Italsocanhandle even <literal>'\0'</literal> as part of

data unlike <type>VARCHAR</type>.

data. It canalso handle <literal>'\0'</literal> as part of

data, unlike <type>VARCHAR</type>.

The data is converted from/to hex format and sent/received by

ecpglib.

</para>

<refentry id="ecpg-sql-declare-statement">

<refnamediv>

<refname>DECLARE STATEMENT</refname>

<refpurpose>declares SQL statement identifier associated with connection</refpurpose>

<refpurpose>declaresaSQL statement identifier associated with connection</refpurpose>

</refnamediv>

<refsynopsisdiv>

<title>Description</title>

<para>

<command>DECLARE STATEMENT</command> declares SQL statement identifier.

SQL statement identifier is associated with connection.

<command>DECLARE STATEMENT</command> declaresaSQL statement identifier

to be associated with connection.

</para>

<para>

<command>DECLARE CURSOR</command> with a SQL statement identifier can be written before PREPARE.

<command>DECLARE CURSOR</command> with an SQL statement identifier

can be written before <command>PREPARE</command>.

</para>

</refsect1>

A database connection name established by the <command>CONNECT</command> command.

</para>

<para>

If AT clause is omitted, an SQL statement identifier is associated with the DEFAULT connection.

If the <literal>AT</literal> clause is omitted, the SQL statement

identifier is associated with the <literal>DEFAULT</literal> connection.

</para>

</listitem>

</varlistentry>

<term><replaceable class="parameter">statement_name</replaceable></term>

<listitem>

<para>

The name of a SQL statement identifier, either as an SQL identifier or a host variable.

The name of the SQL statement identifier, either as an SQL identifier

or a host variable.

</para>

</listitem>

</varlistentry>

<refsect1>

<title>Notes</title>

<para>

AT clause can be used at other dynamic SQL statements. The following table

gives the connected database when AT clause is used at DECLARE STATEMENT

and other dynamic statements.

The <literal>AT</literal> clause can be used with both

<command>DECLARE STATEMENT</command> and other dynamic SQL statements.

The following table illustrates how it affects the selected database

connection.

</para>

<table tocentry="1" id="ecpg-declare-statement-table">

<title>Scenario</title>

<tgroup cols="4">

<thead>

<row>

<entry>

Using Scenario

Usage Scenario

</entry>

<entry>

</entry>

<entry>

Other Dynamic Statements

</entry>

<entry>

Executed Database

Target Database

</entry>

</row>

</thead>

1

</entry>

<entry>

WithoutAT clause

Without<literal>AT</literal>

</entry>

<entry>

WithoutAT clause

Without<literal>AT</literal>

</entry>

<entry>

Default connection

2

</entry>

<entry>

Using AT clause connecting atcon1

With <literal>AT</literal> that connects to <literal>con1</literal>

</entry>

<entry>

WithoutAT clause

Without<literal>AT</literal>

</entry>

<entry>

con1

3

</entry>

<entry>

Using AT clause connecting atcon1

With <literal>AT</literal> that connects to <literal>con1</literal>

</entry>

<entry>

Using AT clause connecting atcon2

With <literal>AT</literal> that connects to <literal>con2</literal>

</entry>

<entry>

con1

4

</entry>

<entry>

WithoutAT clause

Without<literal>AT</literal>

</entry>

<entry>

Using AT clause connecting atcon2

With <literal>AT</literal> that connects to <literal>con2</literal>

</entry>

<entry>

con2

</tgroup>

</table>

<para>

In scenario 4, DECLARE STATEMENT will be ignored.

In scenario 4,<command>DECLARE STATEMENT</command> will be ignored.

</para>

</refsect1>

returning the connection's previous setting.

In <firstterm>TERSE</firstterm> mode, returned messages include

severity, primary text, and position only; this will normally fit on a

single line. Thedefault mode produces messages that include the above

plus any detail, hint, or context fields (these might span multiple

lines). The <firstterm>VERBOSE</firstterm> mode includes all available

fields. The <firstterm>SQLSTATE</firstterm> mode includes only the

error severity and the <symbol>SQLSTATE</symbol> error code, if one is

available (if not, the output is like <firstterm>TERSE</firstterm>

mode).

single line. The<firstterm>DEFAULT</firstterm> mode produces messages

that include the aboveplus any detail, hint, or context fields (these

might span multiplelines). The <firstterm>VERBOSE</firstterm> mode

includes all availablefields. The <firstterm>SQLSTATE</firstterm>

mode includes only theerror severity and the <symbol>SQLSTATE</symbol>

error code, if one isavailable (if not, the output is like

<firstterm>TERSE</firstterm>mode).

</para>

<para>

<xref linkend="sql-reindex"/> can be used safely and easily in all cases.

This command requires an <literal>ACCESS EXCLUSIVE</literal> lock by

default, hence it is often preferable to execute it with its

<literal>CONCURRENTLY</literal> option which requires only a

<literal>CONCURRENTLY</literal> option, which requires only a

<literal>SHARE UPDATE EXCLUSIVE</literal> lock.

</para>

</sect1>

</programlisting>

Secondly, <acronym>MCV</acronym> lists handle a wider range of clause types,

not just equality clauses like functional dependencies.See forexample the

examplerange query, presented earlier:

not just equality clauses like functional dependencies.Forexample,

consider the followingrange query for the same table:

<programlisting>

EXPLAIN (ANALYZE, TIMING OFF) SELECT * FROM t WHERE a &lt;= 49 AND b &gt; 49;

Typed tables implement a subset of the SQL standard. According to

the standard, a typed table has columns corresponding to the

underlying composite type as well as one other column that is

the <quote>self-referencing column</quote>. PostgreSQL does not

support theseself-referencing columns explicitly, but the same

effect can be had using the OID feature.

the <quote>self-referencing column</quote>.

<productname>PostgreSQL</productname> does not supportself-referencing

columns explicitly.

</para>

</refsect2>

only present if the <firstterm>HEAP_HASNULL</firstterm> bit is set in

<structfield>t_infomask</structfield>. If it is present it begins just after

the fixed header and occupies enough bytes to have one bit per data column

(that is, <structfield>t_natts</structfield> bits altogether). In this list of bits, a

(that is, the number of bits that equals the attribute count in

<structfield>t_infomask2</structfield>). In this list of bits, a

1 bit indicates not-null, a 0 bit is a null. When the bitmap is not

present, all columns are assumed not-null.

The object ID is only present if the <firstterm>HEAP_HASOID_OLD</firstterm> bit