1
0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00

Improve libpgeasy API for multiple result sets, add example.

This commit is contained in:
Bruce Momjian
2002-03-04 18:50:21 +00:00
parent e7db8fa80e
commit b2aade0e4b
3 changed files with 157 additions and 123 deletions

View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29:12 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.9 2002/03/04 18:50:20 momjian Exp $
-->
<chapter id="pgeasy">
@ -11,7 +11,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
<para>
Written by Bruce Momjian
(<email>pgman@candle.pha.pa.us</email>)
and last updated 2000-03-30
and last updated 2002-03-04
</para>
</note>
@ -19,13 +19,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
<application>pgeasy</application> allows you to cleanly interface
to the <application>libpq</application> library, more like a 4GL
SQL interface. Refer to <xref linkend="libpq"> for more
information about <application>libpq</application>
information about <application>libpq</application>.
</para>
<para>
It consists of set of simplified C functions that encapsulate the
functionality of <application>libpq</application>.
The functions are:
It consists of a set of simplified C functions that encapsulate the
functionality of <application>libpq</application>. The functions are:
<itemizedlist>
<listitem>
@ -88,53 +87,50 @@ void set_result(PGresult *newres);
</synopsis>
</listitem>
<listitem>
<synopsis>
void unset_result(PGresult *oldres);
</synopsis>
</listitem>
</itemizedlist>
</para>
<para>
Many functions return a structure or value, so you can do more work
Many functions return a structure or value, so you can work
with the result if required.
</para>
<para>
You basically connect to the database with <function>connectdb</function>,
issue your query with <function>doquery</function>,
fetch the results with <function>fetch</function>,
and finish with <function>disconnectdb</function>.
You basically connect to the database with
<function>connectdb</function>, issue your query with
<function>doquery</function>, fetch the results with
<function>fetch</function>, and finish with
<function>disconnectdb</function>.
</para>
<para>
For <literal>SELECT</literal> queries, <function>fetch</function>
allows you to pass pointers as parameters, and on return the variables
are filled with data from the binary cursor you opened. These binary
cursors cannot be used if you are running the
<application>pgeasy</application>
client on a system with a different architecture than the database
server. If you pass a NULL pointer parameter, the column is skipped.
<function>fetchwithnulls</function> allows you to retrieve the NULL
status of the field by passing an <literal>int*</literal>
after each result pointer, which returns true or false if the field is null.
You can always use <application>libpq</application> functions on the <structname>PGresult</structname> pointer returned
by <function>doquery</function>.
<function>reset_fetch</function> starts the fetch back at the beginning.
allows you to pass pointers as parameters, and on return the
variables are filled with data from the binary cursor you opened.
These binary cursors cannot be used if you are running the
<application>pgeasy</application> client on a system with a different
architecture than the database server. If you pass a NULL pointer
parameter, the column is skipped. <function>fetchwithnulls</function>
allows you to retrieve the NULL status of the field by passing an
<literal>int*</literal> after each result pointer, which returns true
or false to indicate if the field is null. You can always use
<application>libpq</application> functions on the
<structname>PGresult</structname> pointer returned by
<function>doquery</function>. <function>reset_fetch</function> starts
the fetch back at the beginning.
</para>
<para>
<function>get_result</function>,
<function>set_result</function>,
and
<function>unset_result</function>
allow you to handle multiple result sets at the same time.
<function>get_result</function> and <function>set_result</function>
allow you to handle multiple open result sets. Use
<function>get_result</function> to save a result into an application
variable. You can then later use <function>set_result</function> to
return to the previously save result.
</para>
<para>
There are several demonstration programs in the
source directory.
There are several demonstration programs in
<filename>pgsql/src/interfaces/libpgeasy/examples</>.
</para>
</chapter>