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Add STRICT to PL/pgSQL SELECT INTO, so exceptions are thrown if more or
less than one row is returned by the SELECT, for Oracle PL/SQL compatibility. Improve SELECT INTO documentation. Matt Miller
1 parent eb5558b commit a584c12

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6 files changed

+78
-44
lines changed

6 files changed

+78
-44
lines changed

‎doc/src/sgml/plpgsql.sgml

Lines changed: 29 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.95 2006/06/12 16:45:30 momjian Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.96 2006/06/15 18:02:22 momjian Exp $ -->
22

33
<chapter id="plpgsql">
44
<title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@@ -1081,7 +1081,7 @@ tax := subtotal * 0.06;
10811081
variable, or list of scalar variables. This is done by:
10821082

10831083
<synopsis>
1084-
SELECT INTO <replaceable>target</replaceable> <replaceable>select_expressions</replaceable> FROM ...;
1084+
SELECT INTO <optional>STRICT</optional> <replaceable>target</replaceable> <replaceable>select_expressions</replaceable> FROM ...;
10851085
</synopsis>
10861086

10871087
where <replaceable>target</replaceable> can be a record variable, a row
@@ -1122,47 +1122,43 @@ SELECT INTO <replaceable>target</replaceable> <replaceable>select_expressions</r
11221122
</para>
11231123

11241124
<para>
1125-
If the query returns zero rows, null values are assigned to the
1126-
target(s). If the query returns multiple rows, the first
1127-
row is assigned to the target(s) and the rest are discarded.
1128-
(Note that <quote>the first row</> is not well-defined unless you've
1129-
used <literal>ORDER BY</>.)
1130-
</para>
1131-
1132-
<para>
1133-
You can check the special <literal>FOUND</literal> variable (see
1134-
<xref linkend="plpgsql-statements-diagnostics">) after a
1135-
<command>SELECT INTO</command> statement to determine whether the
1136-
assignment was successful, that is, at least one row was was returned by
1137-
the query. For example:
1125+
If <literal>STRICT</literal> is not specified then
1126+
<replaceable>target</replaceable> will be set to the first row
1127+
returned by the query, or if the query returned no rows,
1128+
null values are assigned. (Note that <quote>the first row</> is not
1129+
well-defined unless you've used <literal>ORDER BY</>.)
1130+
You can check the special <literal>FOUND</literal> variable to
1131+
determine if any rows were found:
11381132

11391133
<programlisting>
1140-
SELECT INTO myrec * FROM emp WHERE empname = myname;
1134+
SELECT INTO STRICT myrec * FROM emp WHERE empname = myname;
11411135
IF NOT FOUND THEN
11421136
RAISE EXCEPTION 'employee % not found', myname;
11431137
END IF;
11441138
</programlisting>
1145-
</para>
11461139

11471140
<para>
1148-
To test for whether a record/row result is null, you can use the
1149-
<literal>IS NULL</literal> conditional. There is, however, no
1150-
way to tell whether any additional rows might have been
1151-
discarded. Here is an example that handles the case where no
1152-
rows have been returned:
1153-
<programlisting>
1154-
DECLARE
1155-
users_rec RECORD;
1156-
BEGIN
1157-
SELECT INTO users_rec * FROM users WHERE user_id=3;
1141+
If the <literal>STRICT</literal> option is specified, a query must
1142+
return exactly one row or a run-time error will be thrown, either
1143+
<literal>NO_DATA_FOUND</> (no rows) or <literal>TOO_MANY_ROWS</>
1144+
(more than one row). You can must use exception blocks to determine
1145+
the number of rows generated by the query:
11581146

1159-
IF users_rec.homepage IS NULL THEN
1160-
-- user entered no homepage, return "http://"
1161-
RETURN 'http://';
1162-
END IF;
1147+
<programlisting>
1148+
BEGIN;
1149+
SELECT INTO STRICT myrec * FROM emp WHERE empname = myname;
1150+
EXCEPTION
1151+
WHEN NO_DATA_FOUND THEN
1152+
RAISE EXCEPTION 'employee % not found', myname;
1153+
WHEN TOO_MANY_ROWS THEN
1154+
RAISE EXCEPTION 'employee % not unique', myname;
11631155
END;
11641156
</programlisting>
1157+
Only <command>SELECT INTO STRICT</command> allows you to check if more
1158+
than one row was retrieved. <command>SELECT INTO STRICT</command>
1159+
matches Oracle's PL/SQL <command>SELECT INTO</command> behavior.
11651160
</para>
1161+
11661162
</sect2>
11671163

11681164
<sect2 id="plpgsql-statements-perform">
@@ -1424,8 +1420,8 @@ GET DIAGNOSTICS integer_var = ROW_COUNT;
14241420
<itemizedlist>
14251421
<listitem>
14261422
<para>
1427-
A <command>SELECT INTO</command> statement sets
1428-
<literal>FOUND</literal> true if it returns a row, false if no
1423+
A <command>SELECT INTO</command> statement sets
1424+
<literal>FOUND</literal> true if a row is assigned, false if no
14291425
row is returned.
14301426
</para>
14311427
</listitem>

‎src/pl/plpgsql/src/gram.y

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.91 2006/06/12 16:45:30 momjian Exp $
12+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.92 2006/06/15 18:02:22 momjian Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -157,6 +157,7 @@ static void check_labels(const char *start_label,
157157
%token K_ELSE
158158
%token K_ELSIF
159159
%token K_END
160+
%token K_STRICT
160161
%token K_EXCEPTION
161162
%token K_EXECUTE
162163
%token K_EXIT
@@ -2001,6 +2002,7 @@ make_select_stmt(void)
20012002
PLpgSQL_rec *rec = NULL;
20022003
int tok;
20032004
bool have_into = false;
2005+
bool have_strict = false;
20042006

20052007
plpgsql_dstring_init(&ds);
20062008
plpgsql_dstring_append(&ds, "SELECT ");
@@ -2028,6 +2030,11 @@ make_select_stmt(void)
20282030
errmsg("INTO specified more than once")));
20292031
}
20302032
tok = yylex();
2033+
if (tok == K_STRICT)
2034+
{
2035+
have_strict = true;
2036+
tok = yylex();
2037+
}
20312038
switch (tok)
20322039
{
20332040
case T_ROW:
@@ -2108,6 +2115,7 @@ make_select_stmt(void)
21082115
select->rec = rec;
21092116
select->row = row;
21102117
select->query = expr;
2118+
select->strict = have_strict;
21112119

21122120
return (PLpgSQL_stmt *)select;
21132121
}

‎src/pl/plpgsql/src/pl_exec.c

Lines changed: 25 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.170 2006/06/12 16:45:30 momjian Exp $
11+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.171 2006/06/15 18:02:22 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1701,23 +1701,41 @@ exec_stmt_select(PLpgSQL_execstate *estate, PLpgSQL_stmt_select *stmt)
17011701

17021702
/*
17031703
* Run the query
1704+
* Retrieving two rows can be slower than a single row, e.g.
1705+
* a sequential scan where the scan has to be completed to
1706+
* check for a second row. For this reason, we only do the
1707+
* second-line check for STRICT.
17041708
*/
1705-
exec_run_select(estate, stmt->query, 1, NULL);
1709+
exec_run_select(estate, stmt->query, stmt->strict ? 2 : 1, NULL);
17061710
tuptab = estate->eval_tuptable;
17071711
n = estate->eval_processed;
17081712

17091713
/*
1710-
* If the query didn't return any rows, set the target to NULL and return.
1714+
* If SELECT ... INTO specified STRICT, and the query didn't
1715+
* find exactly one row, throw an error. If STRICT was not specified,
1716+
* then allow the query to find any number of rows.
17111717
*/
17121718
if (n == 0)
17131719
{
1714-
exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
1715-
exec_eval_cleanup(estate);
1716-
return PLPGSQL_RC_OK;
1720+
if (!stmt->strict)
1721+
{
1722+
/* null the target */
1723+
exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
1724+
exec_eval_cleanup(estate);
1725+
return PLPGSQL_RC_OK;
1726+
}
1727+
else
1728+
ereport(ERROR,
1729+
(errcode(ERRCODE_NO_DATA),
1730+
errmsg("query returned no rows")));
17171731
}
1732+
else if (n > 1 && stmt->strict)
1733+
ereport(ERROR,
1734+
(errcode(ERRCODE_CARDINALITY_VIOLATION),
1735+
errmsg("query more than one row")));
17181736

17191737
/*
1720-
* Put the result into the target and set found to true
1738+
* Put the first result into the target and set found to true
17211739
*/
17221740
exec_move_row(estate, rec, row, tuptab->vals[0], tuptab->tupdesc);
17231741
exec_set_found(estate, true);

‎src/pl/plpgsql/src/plerrcodes.h

Lines changed: 11 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
* Copyright (c) 2003-2006, PostgreSQL Global Development Group
1111
*
12-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/plerrcodes.h,v 1.7 2006/03/05 15:59:10 momjian Exp $
12+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/plerrcodes.h,v 1.8 2006/06/15 18:02:22 momjian Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -722,3 +722,13 @@
722722
{
723723
"index_corrupted", ERRCODE_INDEX_CORRUPTED
724724
},
725+
726+
{
727+
"no_data_found", ERRCODE_NO_DATA
728+
},
729+
730+
{
731+
"too_many_rows", ERRCODE_CARDINALITY_VIOLATION
732+
},
733+
734+

‎src/pl/plpgsql/src/plpgsql.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.75 2006/06/12 16:45:30 momjian Exp $
11+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.76 2006/06/15 18:02:22 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -432,6 +432,7 @@ typedef struct
432432
{ /* SELECT ... INTO statement */
433433
int cmd_type;
434434
int lineno;
435+
bool strict;
435436
PLpgSQL_rec *rec;
436437
PLpgSQL_row *row;
437438
PLpgSQL_expr *query;

‎src/pl/plpgsql/src/scan.l

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/scan.l,v 1.50 2006/06/12 16:45:30 momjian Exp $
12+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/scan.l,v 1.51 2006/06/15 18:02:22 momjian Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -129,6 +129,7 @@ else { return K_ELSE; }
129129
elseif { return K_ELSIF; }
130130
elsif { return K_ELSIF; }
131131
end { return K_END; }
132+
strict { return K_STRICT; }
132133
exception { return K_EXCEPTION; }
133134
execute { return K_EXECUTE; }
134135
exit { return K_EXIT; }

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