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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
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66
doc/src/sgml/libpgeasy.sgml
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@ -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"> <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> <para>
Written by Bruce Momjian Written by Bruce Momjian
(<email>pgman@candle.pha.pa.us</email>) (<email>pgman@candle.pha.pa.us</email>)
and last updated 2000-03-30 and last updated 2002-03-04
</para> </para>
</note> </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 <application>pgeasy</application> allows you to cleanly interface
to the <application>libpq</application> library, more like a 4GL to the <application>libpq</application> library, more like a 4GL
SQL interface. Refer to <xref linkend="libpq"> for more SQL interface. Refer to <xref linkend="libpq"> for more
information about <application>libpq</application> information about <application>libpq</application>.
</para> </para>
<para> <para>
It consists of set of simplified C functions that encapsulate the It consists of a set of simplified C functions that encapsulate the
functionality of <application>libpq</application>. functionality of <application>libpq</application>. The functions are:
The functions are:
<itemizedlist> <itemizedlist>
<listitem> <listitem>
@ -88,53 +87,50 @@ void set_result(PGresult *newres);
</synopsis> </synopsis>
</listitem> </listitem>
<listitem>
<synopsis>
void unset_result(PGresult *oldres);
</synopsis>
</listitem>
</itemizedlist> </itemizedlist>
</para> </para>
<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. with the result if required.
</para> </para>
<para> <para>
You basically connect to the database with <function>connectdb</function>, You basically connect to the database with
issue your query with <function>doquery</function>, <function>connectdb</function>, issue your query with
fetch the results with <function>fetch</function>, <function>doquery</function>, fetch the results with
and finish with <function>disconnectdb</function>. <function>fetch</function>, and finish with
<function>disconnectdb</function>.
</para> </para>
<para> <para>
For <literal>SELECT</literal> queries, <function>fetch</function> For <literal>SELECT</literal> queries, <function>fetch</function>
allows you to pass pointers as parameters, and on return the variables allows you to pass pointers as parameters, and on return the
are filled with data from the binary cursor you opened. These binary variables are filled with data from the binary cursor you opened.
cursors cannot be used if you are running the These binary cursors cannot be used if you are running the
<application>pgeasy</application> <application>pgeasy</application> client on a system with a different
client on a system with a different architecture than the database architecture than the database server. If you pass a NULL pointer
server. If you pass a NULL pointer parameter, the column is skipped. parameter, the column is skipped. <function>fetchwithnulls</function>
<function>fetchwithnulls</function> allows you to retrieve the NULL allows you to retrieve the NULL status of the field by passing an
status of the field by passing an <literal>int*</literal> <literal>int*</literal> after each result pointer, which returns true
after each result pointer, which returns true or false if the field is null. or false to indicate if the field is null. You can always use
You can always use <application>libpq</application> functions on the <structname>PGresult</structname> pointer returned <application>libpq</application> functions on the
by <function>doquery</function>. <structname>PGresult</structname> pointer returned by
<function>reset_fetch</function> starts the fetch back at the beginning. <function>doquery</function>. <function>reset_fetch</function> starts
the fetch back at the beginning.
</para> </para>
<para> <para>
<function>get_result</function>, <function>get_result</function> and <function>set_result</function>
<function>set_result</function>, allow you to handle multiple open result sets. Use
and <function>get_result</function> to save a result into an application
<function>unset_result</function> variable. You can then later use <function>set_result</function> to
allow you to handle multiple result sets at the same time. return to the previously save result.
</para> </para>
<para> <para>
There are several demonstration programs in the There are several demonstration programs in
source directory. <filename>pgsql/src/interfaces/libpgeasy/examples</>.
</para> </para>
</chapter> </chapter>

12
src/interfaces/libpgeasy/examples/Makefile
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@ -4,23 +4,17 @@
# Makefile for pgeasy examples # Makefile for pgeasy examples
# #
# IDENTIFICATION # IDENTIFICATION
# $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.2 2000/05/18 14:24:37 momjian Exp $ # $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.3 2002/03/04 18:50:21 momjian Exp $
# #
#------------------------------------------------------------------------- #-------------------------------------------------------------------------
CFLAGS=-I/usr/local/pgsql/include CFLAGS=-I/usr/local/pgsql/include
TARGET = pginsert pgwordcount pgnulltest TARGET = pginsert pgwordcount pgnulltest pgmultiresult
LDFLAGS = -L/usr/local/pgsql/lib -lpgeasy LDFLAGS = -L/usr/local/pgsql/lib -lpgeasy
all : $(TARGET) all : $(TARGET)
pginsert: %: %.c
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
pgwordcount:
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
pgnulltest:
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS) gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
clean: clean:

188
src/interfaces/libpgeasy/libpgeasy.c
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@ -6,6 +6,7 @@
#include <stdio.h> #include <stdio.h>
#include <string.h> #include <string.h>
#include <stdarg.h> #include <stdarg.h>
#include <stdlib.h>
#include "libpq-fe.h" #include "libpq-fe.h"
#include "halt.h" #include "halt.h"
@ -34,13 +35,15 @@ static int tuple; /* stores fetch location */
static int on_error_state = ON_ERROR_STOP; /* halt on errors? */ static int on_error_state = ON_ERROR_STOP; /* halt on errors? */
static int in_result_block = FALSE; static int user_has_res = FALSE;
static int was_get_unset_result = FALSE;
static void add_res_tuple(void);
static void get_res_tuple(void);
static void del_res_tuple(void);
/* /*
*
* connectdb - returns PGconn structure * connectdb - returns PGconn structure
*
*/ */
PGconn * PGconn *
connectdb(char *options) connectdb(char *options)
@ -53,17 +56,14 @@ connectdb(char *options)
return conn; return conn;
} }
/* /*
*
* disconnectdb * disconnectdb
*
*/ */
void void
disconnectdb() disconnectdb()
{ {
if (res != NULL && if (res != NULL && user_has_res == FALSE)
in_result_block == FALSE &&
was_get_unset_result == FALSE)
{ {
PQclear(res); PQclear(res);
res = NULL; res = NULL;
@ -72,20 +72,17 @@ disconnectdb()
PQfinish(conn); PQfinish(conn);
} }
/* /*
*
* doquery - returns PGresult structure * doquery - returns PGresult structure
*
*/ */
PGresult * PGresult *
doquery(char *query) doquery(char *query)
{ {
if (res != NULL && if (res != NULL && user_has_res == FALSE)
in_result_block == FALSE &&
was_get_unset_result == FALSE)
PQclear(res); PQclear(res);
was_get_unset_result = FALSE; user_has_res = FALSE;
res = PQexec(conn, query); res = PQexec(conn, query);
if (on_error_state == ON_ERROR_STOP && if (on_error_state == ON_ERROR_STOP &&
@ -105,11 +102,10 @@ doquery(char *query)
return res; return res;
} }
/* /*
*
* fetch - returns tuple number (starts at 0), or the value END_OF_TUPLES * fetch - returns tuple number (starts at 0), or the value END_OF_TUPLES
* NULL pointers are skipped * NULL pointers are skipped
*
*/ */
int int
fetch(void *param,...) fetch(void *param,...)
@ -142,8 +138,8 @@ fetch(void *param,...)
return tuple++; return tuple++;
} }
/* /*
*
* fetchwithnulls - returns tuple number (starts at 0), * fetchwithnulls - returns tuple number (starts at 0),
* or the value END_OF_TUPLES * or the value END_OF_TUPLES
* Returns TRUE or FALSE into null indicator variables * Returns TRUE or FALSE into null indicator variables
@ -185,10 +181,19 @@ fetchwithnulls(void *param,...)
return tuple++; return tuple++;
} }
/*
* reset_fetch
*/
void
reset_fetch()
{
tuple = 0;
}
/* /*
*
* on_error_stop * on_error_stop
*
*/ */
void void
on_error_stop() on_error_stop()
@ -196,10 +201,9 @@ on_error_stop()
on_error_state = ON_ERROR_STOP; on_error_state = ON_ERROR_STOP;
} }
/* /*
*
* on_error_continue * on_error_continue
*
*/ */
void void
on_error_continue() on_error_continue()
@ -209,92 +213,132 @@ on_error_continue()
/* /*
*
* get_result * get_result
*
*/ */
PGresult * PGresult *
get_result() get_result()
{ {
char *cmdstatus = PQcmdStatus(res); if (res == NULL)
halt("get_result called with no result pointer used\n");
was_get_unset_result = TRUE; /* delete it if it is already there; we are about to re-add it */
del_res_tuple();
/* we have to store the fetch location somewhere */ /* we have to store the fetch location */
/* XXX THIS IS A NO-NO */ add_res_tuple();
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple)); user_has_res = TRUE;
return res; return res;
} }
/* /*
*
* set_result * set_result
*
*/ */
void void
set_result(PGresult *newres) set_result(PGresult *newres)
{ {
char *cmdstatus = PQcmdStatus(res);
if (newres == NULL) if (newres == NULL)
halt("set_result called with null result pointer\n"); halt("set_result called with null result pointer\n");
if (res != NULL && was_get_unset_result == FALSE) if (res != NULL && user_has_res == FALSE)
{ {
if (in_result_block == FALSE) /*
* Basically, throw away res. We can't return to it because the
* user doesn't have the res pointer.
*/
del_res_tuple();
PQclear(res); PQclear(res);
else
{
/* XXX THIS IS A NO-NO */
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
}
} }
in_result_block = TRUE; user_has_res = FALSE;
was_get_unset_result = FALSE;
cmdstatus = PQcmdStatus(newres);
memcpy(&tuple, &cmdstatus[1], sizeof(tuple));
res = newres; res = newres;
get_res_tuple();
} }
/* /*
* * Routines to store res/tuple mapping
* unset_result * This is used to keep track of fetch locations while using get/set on
* * result sets.
* Auto-growing array is used, with empty slots marked by res == NULL
*/ */
void
unset_result(PGresult *oldres) static struct res_tuple
{ {
char *cmdstatus = PQcmdStatus(oldres); PGresult *res;
int tuple;
} *res_tuple = NULL;
if (oldres == NULL) static int res_tuple_len = 0;
halt("unset_result called with null result pointer\n");
if (in_result_block == FALSE)
halt("Unset of result without being set.\n");
was_get_unset_result = TRUE;
/* XXX THIS IS A NO-NO */
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
in_result_block = FALSE;
}
/* /*
* * add_res_tuple
* reset_fetch
*
*/ */
void static void
reset_fetch() add_res_tuple(void)
{ {
tuple = 0; int i,
new_res_tuple_len = res_tuple_len ? res_tuple_len * 2 : 1;
for (i = 0; i < res_tuple_len; i++)
/* Put it in an empty slot */
if (res_tuple[i].res == NULL)
{
res_tuple[i].res = res;
res_tuple[i].tuple = tuple;
}
/* Need to grow array */
res_tuple = realloc(res_tuple, new_res_tuple_len * sizeof(struct res_tuple));
/* clear new elements */
for (i = res_tuple_len; i < new_res_tuple_len; i++)
{
res_tuple[i].res = NULL;
res_tuple[i].tuple = 0;
}
/* recursion to add entry */
add_res_tuple();
}
/*
* get_res_tuple
*/
static void
get_res_tuple(void)
{
int i;
for (i = 0; i < res_tuple_len; i++)
if (res_tuple[i].res == res)
{
tuple = res_tuple[i].tuple;
return;
}
halt("get_res_tuple called with invalid result pointer\n");
}
/*
* del_res_tuple
*/
static void
del_res_tuple(void)
{
int i;
for (i = 0; i < res_tuple_len; i++)
if (res_tuple[i].res == res)
{
res_tuple[i].res = NULL;
return;
}
return;
} }