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This patch improves the behavior of FOUND in PL/PgSQL. In Oracle,

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FOUND is set whenever a SELECT INTO returns > 0 rows, *or* when an
INSERT, UPDATE, or DELETE affects > 0 rows. We implemented the first
part of this behavior, but not the second.

I also improved the documentation on the various situations in which
FOUND can be set (excluding inside FOR loops, which I still need to
think about), and added some regression tests for this behavior.

Neil Conway
This commit is contained in:
Bruce Momjian
2002-08-20 05:28:24 +00:00
parent 818a33e4d5
commit ebe1be1321
4 changed files with 288 additions and 129 deletions
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72
doc/src/sgml/plpgsql.sgml
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@ -1,5 +1,5 @@
<!-- <!--
$Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.1 2002/07/30 19:36:10 momjian Exp $ $Header: /cvsroot/pgsql/doc/src/sgml/plpgsql.sgml,v 1.2 2002/08/20 05:28:23 momjian Exp $
--> -->
<chapter id="plpgsql"> <chapter id="plpgsql">
@ -126,7 +126,7 @@ END;
them to define operators or use them in functional indexes. them to define operators or use them in functional indexes.
</para> </para>
<sect2 id="plpgsql-advantages"> <sect2 id="plpgsql-advantages">
<title>Advantages of Using PL/pgSQL</title> <title>Advantages of Using <application>PL/pgSQL</application></title>
<itemizedlist> <itemizedlist>
<listitem> <listitem>
@ -852,10 +852,58 @@ SELECT INTO <replaceable>target</replaceable> <replaceable>expressions</replacea
</para> </para>
<para> <para>
There is a special variable named FOUND of type There is a special variable named <literal>FOUND</literal> of
<type>boolean</type> that can be used immediately after a SELECT type <type>boolean</type>. The initial value of
INTO to check if an assignment had success (that is, at least one <literal>FOUND</literal> is false; it is set to true when one of
row was returned by the SELECT). For example, the following events occurs:
<itemizedlist>
<listitem>
<para>
A SELECT INTO statement is executed, and it returns one or
more rows.
</para>
</listitem>
<listitem>
<para>
A UPDATE, INSERT, or DELETE statement is executed, and it
affects one or more rows.
</para>
</listitem>
<listitem>
<para>
A PERFORM statement is executed, and it discards one or more
rows.
</para>
</listitem>
<listitem>
<para>
A FETCH statement is executed, and it returns an additional
row.
</para>
</listitem>
<listitem>
<para>
A FOR statement is executed, and it iterates one or more
times. This applies to all three variants of the FOR statement
(integer FOR loops, record-set FOR loops, and dynamic
record-set FOR loops). <literal>FOUND</literal> is only set
when the FOR loop exits: inside the execution of the loop,
<literal>FOUND</literal> is not modified, although it may be
set by the execution of other statements.
</para>
</listitem>
</itemizedlist>
If none of these events occur, <literal>FOUND</literal> is set to
false. <literal>FOUND</literal> is a local variable; any changes
to it effect only the current <application>PL/pgSQL</application>
function.
</para>
<para>
You can use <literal>FOUND</literal> immediately after a SELECT
INTO statement to determine whether the assignment was successful
(that is, at least one row was was returned by the SELECT
statement). For example:
<programlisting> <programlisting>
SELECT INTO myrec * FROM EMP WHERE empname = myname; SELECT INTO myrec * FROM EMP WHERE empname = myname;
@ -902,10 +950,10 @@ PERFORM <replaceable>query</replaceable>;
This executes a <literal>SELECT</literal> This executes a <literal>SELECT</literal>
<replaceable>query</replaceable> and discards the <replaceable>query</replaceable> and discards the
result. <application>PL/pgSQL</application> variables are substituted result. <application>PL/pgSQL</application> variables are
in the query as usual. Also, the special variable FOUND is set to substituted in the query as usual. Also, the special variable
true if the query produced at least one row, or false if it produced <literal>FOUND</literal> is set to true if the query produced at
no rows. least one row, or false if it produced no rows.
</para> </para>
<note> <note>
@ -1638,8 +1686,8 @@ FETCH <replaceable>cursor</replaceable> INTO <replaceable>target</replaceable>;
FETCH retrieves the next row from the cursor into a target, FETCH retrieves the next row from the cursor into a target,
which may be a row variable, a record variable, or a comma-separated which may be a row variable, a record variable, or a comma-separated
list of simple variables, just like SELECT INTO. As with list of simple variables, just like SELECT INTO. As with
SELECT INTO, the special variable FOUND may be checked to see SELECT INTO, the special variable <literal>FOUND</literal> may be
whether a row was obtained or not. checked to see whether a row was obtained or not.
<programlisting> <programlisting>
FETCH curs1 INTO rowvar; FETCH curs1 INTO rowvar;

245
src/pl/plpgsql/src/pl_exec.c
View File

@ -3,7 +3,7 @@
* procedural language * procedural language
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.56 2002/06/24 23:12:06 tgl Exp $ * $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.57 2002/08/20 05:28:23 momjian Exp $
* *
* This software is copyrighted by Jan Wieck - Hamburg. * This software is copyrighted by Jan Wieck - Hamburg.
* *
@ -1180,7 +1180,8 @@ exec_stmt_fori(PLpgSQL_execstate * estate, PLpgSQL_stmt_fori * stmt)
Datum value; Datum value;
Oid valtype; Oid valtype;
bool isnull = false; bool isnull = false;
int rc; bool found = false;
int rc = PLPGSQL_RC_OK;
var = (PLpgSQL_var *) (estate->datums[stmt->var->varno]); var = (PLpgSQL_var *) (estate->datums[stmt->var->varno]);
@ -1213,7 +1214,6 @@ exec_stmt_fori(PLpgSQL_execstate * estate, PLpgSQL_stmt_fori * stmt)
/* /*
* Now do the loop * Now do the loop
*/ */
exec_set_found(estate, false);
for (;;) for (;;)
{ {
/* /*
@ -1229,36 +1229,36 @@ exec_stmt_fori(PLpgSQL_execstate * estate, PLpgSQL_stmt_fori * stmt)
if ((int4) (var->value) > (int4) value) if ((int4) (var->value) > (int4) value)
break; break;
} }
exec_set_found(estate, true);
found = true; /* looped at least once */
/* /*
* Execute the statements * Execute the statements
*/ */
rc = exec_stmts(estate, stmt->body); rc = exec_stmts(estate, stmt->body);
/* if (rc == PLPGSQL_RC_RETURN)
* Check returncode break; /* return from function */
*/ else if (rc == PLPGSQL_RC_EXIT)
switch (rc)
{ {
case PLPGSQL_RC_OK: if (estate->exitlabel == NULL)
break; /* unlabelled exit, finish the current loop */
rc = PLPGSQL_RC_OK;
case PLPGSQL_RC_EXIT: else if (stmt->label != NULL &&
if (estate->exitlabel == NULL) strcmp(stmt->label, estate->exitlabel) == 0)
return PLPGSQL_RC_OK; {
if (stmt->label == NULL) /* labelled exit, matches the current stmt's label */
return PLPGSQL_RC_EXIT;
if (strcmp(stmt->label, estate->exitlabel))
return PLPGSQL_RC_EXIT;
estate->exitlabel = NULL; estate->exitlabel = NULL;
return PLPGSQL_RC_OK; rc = PLPGSQL_RC_OK;
}
case PLPGSQL_RC_RETURN: /*
return PLPGSQL_RC_RETURN; * otherwise, we processed a labelled exit that does not
* match the current statement's label, if any: return
* RC_EXIT so that the EXIT continues to recurse upward.
*/
default: break;
elog(ERROR, "unknown rc %d from exec_stmts()", rc);
} }
/* /*
@ -1270,7 +1270,15 @@ exec_stmt_fori(PLpgSQL_execstate * estate, PLpgSQL_stmt_fori * stmt)
var->value++; var->value++;
} }
return PLPGSQL_RC_OK; /*
* Set the FOUND variable to indicate the result of executing the
* loop (namely, whether we looped one or more times). This must be
* set here so that it does not interfere with the value of the
* FOUND variable inside the loop processing itself.
*/
exec_set_found(estate, found);
return rc;
} }
@ -1288,15 +1296,11 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
PLpgSQL_row *row = NULL; PLpgSQL_row *row = NULL;
SPITupleTable *tuptab; SPITupleTable *tuptab;
Portal portal; Portal portal;
int rc; bool found = false;
int rc = PLPGSQL_RC_OK;
int i; int i;
int n; int n;
/*
* Initialize the global found variable to false
*/
exec_set_found(estate, false);
/* /*
* Determine if we assign to a record or a row * Determine if we assign to a record or a row
*/ */
@ -1321,25 +1325,18 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
tuptab = SPI_tuptable; tuptab = SPI_tuptable;
/* /*
* If the query didn't return any row, set the target to NULL and * If the query didn't return any rows, set the target to NULL and
* return. * return with FOUND = false.
*/ */
if (n == 0) if (n == 0)
{
exec_move_row(estate, rec, row, NULL, NULL); exec_move_row(estate, rec, row, NULL, NULL);
SPI_cursor_close(portal); else
return PLPGSQL_RC_OK; found = true; /* processed at least one tuple */
}
/*
* There are tuples, so set found to true
*/
exec_set_found(estate, true);
/* /*
* Now do the loop * Now do the loop
*/ */
for (;;) while (n > 0)
{ {
for (i = 0; i < n; i++) for (i = 0; i < n; i++)
{ {
@ -1353,35 +1350,36 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
*/ */
rc = exec_stmts(estate, stmt->body); rc = exec_stmts(estate, stmt->body);
/* if (rc != PLPGSQL_RC_OK)
* Check returncode
*/
switch (rc)
{ {
case PLPGSQL_RC_OK: /*
break; * We're aborting the loop, so cleanup and set FOUND
*/
case PLPGSQL_RC_EXIT: exec_set_found(estate, found);
SPI_freetuptable(tuptab); SPI_freetuptable(tuptab);
SPI_cursor_close(portal); SPI_cursor_close(portal);
if (rc == PLPGSQL_RC_EXIT)
{
if (estate->exitlabel == NULL) if (estate->exitlabel == NULL)
return PLPGSQL_RC_OK; /* unlabelled exit, finish the current loop */
if (stmt->label == NULL) rc = PLPGSQL_RC_OK;
return PLPGSQL_RC_EXIT; else if (stmt->label != NULL &&
if (strcmp(stmt->label, estate->exitlabel)) strcmp(stmt->label, estate->exitlabel) == 0)
return PLPGSQL_RC_EXIT; {
estate->exitlabel = NULL; /* labelled exit, matches the current stmt's label */
return PLPGSQL_RC_OK; estate->exitlabel = NULL;
rc = PLPGSQL_RC_OK;
}
case PLPGSQL_RC_RETURN: /*
SPI_freetuptable(tuptab); * otherwise, we processed a labelled exit that does not
SPI_cursor_close(portal); * match the current statement's label, if any: return
* RC_EXIT so that the EXIT continues to recurse upward.
*/
}
return PLPGSQL_RC_RETURN; return rc;
default:
elog(ERROR, "unknown rc %d from exec_stmts()", rc);
} }
} }
@ -1393,9 +1391,6 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
SPI_cursor_fetch(portal, true, 50); SPI_cursor_fetch(portal, true, 50);
n = SPI_processed; n = SPI_processed;
tuptab = SPI_tuptable; tuptab = SPI_tuptable;
if (n == 0)
break;
} }
/* /*
@ -1403,14 +1398,22 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
*/ */
SPI_cursor_close(portal); SPI_cursor_close(portal);
return PLPGSQL_RC_OK; /*
* Set the FOUND variable to indicate the result of executing the
* loop (namely, whether we looped one or more times). This must be
* set here so that it does not interfere with the value of the
* FOUND variable inside the loop processing itself.
*/
exec_set_found(estate, found);
return rc;
} }
/* ---------- /* ----------
* exec_stmt_select Run a query and assign the first * exec_stmt_select Run a query and assign the first
* row to a record or rowtype. * row to a record or rowtype.
* ---------- * ----------
*/ */
static int static int
exec_stmt_select(PLpgSQL_execstate * estate, PLpgSQL_stmt_select * stmt) exec_stmt_select(PLpgSQL_execstate * estate, PLpgSQL_stmt_select * stmt)
@ -1845,6 +1848,11 @@ exec_stmt_execsql(PLpgSQL_execstate * estate,
PLpgSQL_expr *expr = stmt->sqlstmt; PLpgSQL_expr *expr = stmt->sqlstmt;
bool isnull; bool isnull;
/*
* Set magic FOUND variable to false
*/
exec_set_found(estate, false);
/* /*
* On the first call for this expression generate the plan * On the first call for this expression generate the plan
*/ */
@ -1921,9 +1929,18 @@ exec_stmt_execsql(PLpgSQL_execstate * estate,
{ {
case SPI_OK_UTILITY: case SPI_OK_UTILITY:
case SPI_OK_SELINTO: case SPI_OK_SELINTO:
break;
/*
* If the INSERT, DELETE, or UPDATE query affected at least
* one tuple, set the magic 'FOUND' variable to true. This
* conforms with the behavior of PL/SQL.
*/
case SPI_OK_INSERT: case SPI_OK_INSERT:
case SPI_OK_DELETE: case SPI_OK_DELETE:
case SPI_OK_UPDATE: case SPI_OK_UPDATE:
if (SPI_processed > 0)
exec_set_found(estate, true);
break; break;
case SPI_OK_SELECT: case SPI_OK_SELECT:
@ -1931,8 +1948,7 @@ exec_stmt_execsql(PLpgSQL_execstate * estate,
"\n\tIf you want to discard the results, use PERFORM instead."); "\n\tIf you want to discard the results, use PERFORM instead.");
default: default:
elog(ERROR, "error executing query \"%s\"", elog(ERROR, "error executing query \"%s\"", expr->query);
expr->query);
} }
/* /*
@ -2078,7 +2094,7 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
PLpgSQL_rec *rec = NULL; PLpgSQL_rec *rec = NULL;
PLpgSQL_row *row = NULL; PLpgSQL_row *row = NULL;
SPITupleTable *tuptab; SPITupleTable *tuptab;
int rc; int rc = PLPGSQL_RC_OK;
int i; int i;
int n; int n;
HeapTuple typetup; HeapTuple typetup;
@ -2086,11 +2102,7 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
FmgrInfo finfo_output; FmgrInfo finfo_output;
void *plan; void *plan;
Portal portal; Portal portal;
bool found = false;
/*
* Initialize the global found variable to false
*/
exec_set_found(estate, false);
/* /*
* Determine if we assign to a record or a row * Determine if we assign to a record or a row
@ -2153,25 +2165,18 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
tuptab = SPI_tuptable; tuptab = SPI_tuptable;
/* /*
* If the query didn't return any row, set the target to NULL and * If the query didn't return any rows, set the target to NULL and
* return. * return with FOUND = false.
*/ */
if (n == 0) if (n == 0)
{
exec_move_row(estate, rec, row, NULL, NULL); exec_move_row(estate, rec, row, NULL, NULL);
SPI_cursor_close(portal); else
return PLPGSQL_RC_OK; found = true;
}
/*
* There are tuples, so set found to true
*/
exec_set_found(estate, true);
/* /*
* Now do the loop * Now do the loop
*/ */
for (;;) while (n > 0)
{ {
for (i = 0; i < n; i++) for (i = 0; i < n; i++)
{ {
@ -2186,34 +2191,35 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
rc = exec_stmts(estate, stmt->body); rc = exec_stmts(estate, stmt->body);
/* /*
* Check returncode * We're aborting the loop, so cleanup and set FOUND
*/ */
switch (rc) if (rc != PLPGSQL_RC_OK)
{ {
case PLPGSQL_RC_OK: exec_set_found(estate, found);
break; SPI_freetuptable(tuptab);
SPI_cursor_close(portal);
case PLPGSQL_RC_EXIT:
SPI_freetuptable(tuptab);
SPI_cursor_close(portal);
if (rc == PLPGSQL_RC_EXIT)
{
if (estate->exitlabel == NULL) if (estate->exitlabel == NULL)
return PLPGSQL_RC_OK; /* unlabelled exit, finish the current loop */
if (stmt->label == NULL) rc = PLPGSQL_RC_OK;
return PLPGSQL_RC_EXIT; else if (stmt->label != NULL &&
if (strcmp(stmt->label, estate->exitlabel)) strcmp(stmt->label, estate->exitlabel) == 0)
return PLPGSQL_RC_EXIT; {
estate->exitlabel = NULL; /* labelled exit, matches the current stmt's label */
return PLPGSQL_RC_OK; estate->exitlabel = NULL;
rc = PLPGSQL_RC_OK;
}
case PLPGSQL_RC_RETURN: /*
SPI_freetuptable(tuptab); * otherwise, we processed a labelled exit that does not
SPI_cursor_close(portal); * match the current statement's label, if any: return
* RC_EXIT so that the EXIT continues to recurse upward.
*/
}
return PLPGSQL_RC_RETURN; return rc;
default:
elog(ERROR, "unknown rc %d from exec_stmts()", rc);
} }
} }
@ -2225,9 +2231,6 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
SPI_cursor_fetch(portal, true, 50); SPI_cursor_fetch(portal, true, 50);
n = SPI_processed; n = SPI_processed;
tuptab = SPI_tuptable; tuptab = SPI_tuptable;
if (n == 0)
break;
} }
/* /*
@ -2235,6 +2238,14 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
*/ */
SPI_cursor_close(portal); SPI_cursor_close(portal);
/*
* Set the FOUND variable to indicate the result of executing the
* loop (namely, whether we looped one or more times). This must be
* set here so that it does not interfere with the value of the
* FOUND variable inside the loop processing itself.
*/
exec_set_found(estate, found);
return PLPGSQL_RC_OK; return PLPGSQL_RC_OK;
} }
@ -2615,7 +2626,7 @@ exec_stmt_close(PLpgSQL_execstate * estate, PLpgSQL_stmt_close * stmt)
/* ---------- /* ----------
* exec_assign_expr Put an expressions result into * exec_assign_expr Put an expression's result into
* a variable. * a variable.
* ---------- * ----------
*/ */

56
src/test/regress/expected/plpgsql.out
View File

@ -1534,3 +1534,59 @@ SELECT recursion_test(4,3);
4,3,2,1,3 4,3,2,1,3
(1 row) (1 row)
--
-- Test the FOUND magic variable
--
CREATE TABLE found_test_tbl (a int);
create function test_found ()
returns boolean as '
declare
begin
insert into found_test_tbl values (1);
if FOUND then
insert into found_test_tbl values (2);
end if;
update found_test_tbl set a = 100 where a = 1;
if FOUND then
insert into found_test_tbl values (3);
end if;
delete from found_test_tbl where a = 9999; -- matches no rows
if not FOUND then
insert into found_test_tbl values (4);
end if;
for i in 1 .. 10 loop
-- no need to do anything
end loop;
if FOUND then
insert into found_test_tbl values (5);
end if;
-- never executes the loop
for i in 2 .. 1 loop
-- no need to do anything
end loop;
if not FOUND then
insert into found_test_tbl values (6);
end if;
return true;
end;' language 'plpgsql';
select test_found();
test_found
------------
t
(1 row)
select * from found_test_tbl;
a
-----
2
100
3
4
5
6
(6 rows)

44
src/test/regress/sql/plpgsql.sql
View File

@ -1414,3 +1414,47 @@ BEGIN
END;' LANGUAGE 'plpgsql'; END;' LANGUAGE 'plpgsql';
SELECT recursion_test(4,3); SELECT recursion_test(4,3);
--
-- Test the FOUND magic variable
--
CREATE TABLE found_test_tbl (a int);
create function test_found ()
returns boolean as '
declare
begin
insert into found_test_tbl values (1);
if FOUND then
insert into found_test_tbl values (2);
end if;
update found_test_tbl set a = 100 where a = 1;
if FOUND then
insert into found_test_tbl values (3);
end if;
delete from found_test_tbl where a = 9999; -- matches no rows
if not FOUND then
insert into found_test_tbl values (4);
end if;
for i in 1 .. 10 loop
-- no need to do anything
end loop;
if FOUND then
insert into found_test_tbl values (5);
end if;
-- never executes the loop
for i in 2 .. 1 loop
-- no need to do anything
end loop;
if not FOUND then
insert into found_test_tbl values (6);
end if;
return true;
end;' language 'plpgsql';
select test_found();
select * from found_test_tbl;