<para>

Time zones, and time-zone conventions, are influenced by

political decisions, not just earth geometry. Time zones around the

but continue to be prone to arbitrary changes, particularly with

respect to daylight-savings rules.

<productname>PostgreSQL</productname> uses the widely-used

<parameter>schema</> is the schema name that the object belongs in, or

<literal>NULL</> for object types that do not belong to schemas;

<parameter>name</> is the name of the object, quoted if necessary, only

identifier of the object, otherwise <literal>NULL</>;

<parameter>identity</> is the complete object identity, with the precise format

depending on object type, and each part within the format being

<entry><type>text</type></entry>

<entry>

Name of the object, if the combination of schema and name can be

No quoting is applied, and name is never schema-qualified.

</entry>

</row>

correctly. Advisory locks can be useful for locking strategies

that are an awkward fit for the MVCC model.

For example, a common use of advisory locks is to emulate pessimistic

management systems.

While a flag stored in a table could be used for the same purpose,

advisory locks are faster, avoid table bloat, and are automatically

<para>

By default, or when <literal>uniform</> is specified, all values in the

or <literal>exponential</> options modifies this behavior; each

requires a mandatory threshold which determines the precise shape of the

distribution.

(useful when multiple scripts were specified with <option>-f</>),

and <replaceable>time_epoch</>/<replaceable>time_us</> are a

UNIX epoch format timestamp and an offset

timestamp with fractional seconds) showing when

the transaction completed.

</para>

</synopsis>

<para>

Encrypt <parameter>data</> with a public PGP key <parameter>key</>.

</para>

<para>

The <parameter>options</> parameter can contain option settings,

Sometimes it is desirable to write Tcl functions that are not restricted

to safe Tcl. For example, one might want a Tcl function that sends

email. To handle these cases, there is a variant of <application>PL/Tcl</> called <literal>PL/TclU</>

Tcl interpreter is used. <emphasis>If <application>PL/TclU</> is used, it must be

installed as an untrusted procedural language</emphasis> so that only

database superusers can create functions in it. The writer of a <application>PL/TclU</>

statements in <literal>WITH</>, the order in which the specified updates

actually happen is unpredictable. All the statements are executed with

the same <firstterm>snapshot</> (see <xref linkend="mvcc">), so they

alleviates the effects of the unpredictability of the actual order of row

updates, and means that <literal>RETURNING</> data is the only way to

communicate changes between different <literal>WITH</> sub-statements and

</programlisting>

<para>

and removes the stopword option entirely.

</para>

COMMENT ON TABLE my_schema.my_table IS 'Employee Information';

COMMENT ON TABLESPACE my_tablespace IS 'Tablespace for indexes';

COMMENT ON TEXT SEARCH CONFIGURATION my_config IS 'Special word filtering';

COMMENT ON TEXT SEARCH PARSER my_parser IS 'Splits text into words';

COMMENT ON TEXT SEARCH TEMPLATE snowball IS 'Snowball stemmer';

COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI';

is also acquired by any <command>DELETE</> on a row, and also by an

<command>UPDATE</> that modifies the values on certain columns. Currently,

the set of columns considered for the <command>UPDATE</> case are those that

indexes and expressional indexes are not considered), but this may change

in the future.

Also, if an <command>UPDATE</command>, <command>DELETE</command>,