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In PQnotifies discussion, reference PQsocket as function needed to get

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file descriptor number for select().  (Suggestion from Ken Wright.)
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Tom Lane
2000-03-26 01:00:17 +00:00
parent d2684ea712
commit cb3b3eda9a
1 changed files with 9 additions and 5 deletions
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14
doc/src/sgml/libpq.sgml
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@ -1460,13 +1460,17 @@ deprecated as a waste of processing power.
<para> <para>
A better way to check for NOTIFY A better way to check for NOTIFY
messages when you have no useful queries to make is to call messages when you have no useful queries to make is to call
<function>PQconsumeInput()</function>, then check <function>PQnotifies()</function>. <function>PQconsumeInput()</function>, then check
<function>PQnotifies()</function>.
You can use <function>select</function>(2) to wait for backend data to You can use <function>select</function>(2) to wait for backend data to
arrive, thereby using no <acronym>CPU</acronym> power unless there is something arrive, thereby using no <acronym>CPU</acronym> power unless there is something
to do. Note that this will work OK whether you use <function>PQsendQuery</function>/ to do. (See <function>PQsocket()</function> to obtain the file descriptor
<function>PQgetResult</function> or simply <function>PQexec</function> for number to use with <function>select</function>.)
queries. You should, however, remember to check <function>PQnotifies()</function> Note that this will work OK whether you submit queries with
after each <function>PQgetResult</function> or <function>PQexec</function> to see <function>PQsendQuery</function>/<function>PQgetResult</function> or simply
use <function>PQexec</function>. You should, however, remember to
check <function>PQnotifies()</function> after each
<function>PQgetResult</function> or <function>PQexec</function>, to see
if any notifications came in during the processing of the query. if any notifications came in during the processing of the query.
</para> </para>