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<chapter Id="runtime-config">

<title>Server Configuration</title>

<listitem>

<para>

Abort any statement that takes over the specified number of

milliseconds. If <varname>log_min_error_statement</> is set to

milliseconds, starting from the time the command arrives at the server

from the client. If <varname>log_min_error_statement</> is set to

<literal>ERROR</> or lower, the statement that timed out will also be

logged. A value of zero (the default) turns off the

limitation.

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<chapter id="functions">

<title>Functions and Operators</title>

<indexterm>

<primary>now</primary>

</indexterm>

<indexterm>

<primary>transaction_timestamp</primary>

</indexterm>

<indexterm>

<primary>statement_timestamp</primary>

</indexterm>

<indexterm>

<primary>clock_timestamp</primary>

</indexterm>

<indexterm>

<primary>timeofday</primary>

</indexterm>

<row>

<entry><literal><function>current_timestamp</function></literal></entry>

<entry><type>timestamp with time zone</type></entry>

<entry>Date and time; see <xref linkend="functions-datetime-current">

<entry>Date and time of start of current transaction; see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

<row>

<entry><literal><function>now</function>()</literal></entry>

<entry><type>timestamp with time zone</type></entry>

<entry>Current date and time (equivalent to

<function>current_timestamp</function>); see <xref linkend="functions-datetime-current">

<entry>Date and time of start of current transaction (equivalent to

<function>CURRENT_TIMESTAMP</function>); see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

</row>

<row>

<entry><literal><function>transaction_timestamp</function>()</literal></entry>

<entry><type>timestamp with time zone</type></entry>

<entry>Date and time of start of current transaction (equivalent to

<function>CURRENT_TIMESTAMP</function>); see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

</row>

<row>

<entry><literal><function>statement_timestamp</function>()</literal></entry>

<entry><type>timestamp with time zone</type></entry>

<entry>Date and time of start of current statement; see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

</row>

<row>

<entry><literal><function>clock_timestamp</function>()</literal></entry>

<entry><type>timestamp with time zone</type></entry>

<entry>Current date and time (changes during statement execution); see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

<row>

<entry><literal><function>timeofday</function>()</literal></entry>

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

<entry>Current date and time; see <xref linkend="functions-datetime-current">

<entry>Current date and time (like <function>clock_timestamp</>), but as a Unix-style <type>text</> value;

see <xref linkend="functions-datetime-current">

</entry>

<entry></entry>

<entry></entry>

</sect2>

<sect2 id="functions-datetime-current">

<title>CurrentDate/Time</title>

<title>Date/Time of Transaction Start</title>

<indexterm>

<primary>date</primary>

</indexterm>

<para>

The following functions are available to obtain thecurrentdate and/or

time:

The following functions are available to obtain the date and/or

time of the start of the current transaction:

<synopsis>

CURRENT_DATE

CURRENT_TIME

</screen>

</para>

<para>

The function <function>now()</function> is the traditional

<productname>PostgreSQL</productname> equivalent to

<function>CURRENT_TIMESTAMP</function>.

</para>

<para>

It is important to know that

<function>CURRENT_TIMESTAMP</function> and related functions return

the intent is to allow a single transaction to have a consistent

notion of the <quote>current</quote> time, so that multiple

modifications within the same transaction bear the same

time stamp.

time stamp. Consider using <function>statement_timestamp</> or

<function>clock_timestamp</> if you need something that changes

more frequently.

</para>

<note>

<para>

Other database systems may advance these values more

frequently.

</para>

</note>

<para>

<function>CURRENT_TIMESTAMP</> might not be the

transaction start time on other database systems.

For this reason, and for completeness,

<function>transaction_timestamp</> is provided.

The function <function>now()</function> is the traditional

<productname>PostgreSQL</productname> equivalent to

the SQL-standard <function>CURRENT_TIMESTAMP</function>.

</para>

<para>

There is also the function<function>timeofday()</function> which

returnsthewall-clock time and advances during transactions. For

<type>text</type>stringrather than a <type>timestamp</type>

<function>STATEMENT_TIMESTAMP</> is the time the statement

arrived attheserver from the client. It is not the time

sent as a single querystringto the server, each command

</para>

<para>

staticTimestampTzxactStartTimestamp;

staticTimestampTzstmtStartTimestamp;

returnxactStartTimestamp;

}

GetCurrentStatementStartTimestamp(void)

{

returnstmtStartTimestamp;

}

SetCurrentStatementStartTimestamp(void)

{

stmtStartTimestamp=GetCurrentTimestamp();

}

XactLockTableInsert(s->transactionId);

xactStartTimestamp=GetCurrentTimestamp();

xactStartTimestamp=stmtStartTimestamp;