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Commit6441028

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Add trivial NULL statement to plpgsql, for Oracle compatibility.
1 parentbc91389 commit6441028

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2 files changed

+77
-18
lines changed

2 files changed

+77
-18
lines changed

‎doc/src/sgml/plpgsql.sgml

Lines changed: 54 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.45 2004/08/08 22:40:46 tgl Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.46 2004/08/16 17:52:06 tgl Exp $
33
-->
44

55
<chapter id="plpgsql">
@@ -1098,6 +1098,52 @@ PERFORM create_mv('cs_session_page_requests_mv', my_query);
10981098
</para>
10991099
</sect2>
11001100

1101+
<sect2 id="plpgsql-statements-null">
1102+
<title>Doing Nothing At All</title>
1103+
1104+
<para>
1105+
Sometimes a placeholder statement that does nothing is useful.
1106+
For example, it can indicate that one arm of an if/then/else
1107+
chain is deliberately empty. For this purpose, use the
1108+
<command>NULL</command> statement:
1109+
1110+
<synopsis>
1111+
NULL;
1112+
</synopsis>
1113+
</para>
1114+
1115+
<para>
1116+
For example, the following two fragments of code are equivalent:
1117+
<programlisting>
1118+
BEGIN
1119+
y := x / 0;
1120+
EXCEPTION
1121+
WHEN division_by_zero THEN
1122+
NULL; -- ignore the error
1123+
END;
1124+
</programlisting>
1125+
1126+
<programlisting>
1127+
BEGIN
1128+
y := x / 0;
1129+
EXCEPTION
1130+
WHEN division_by_zero THEN -- ignore the error
1131+
END;
1132+
</programlisting>
1133+
Which is preferable is a matter of taste.
1134+
</para>
1135+
1136+
<note>
1137+
<para>
1138+
In Oracle's PL/SQL, empty statement lists are not allowed, and so
1139+
<command>NULL</> statements are <emphasis>required</> for situations
1140+
such as this. <application>PL/pgSQL</application> allows you to
1141+
just write nothing, instead.
1142+
</para>
1143+
</note>
1144+
1145+
</sect2>
1146+
11011147
<sect2 id="plpgsql-statements-executing-dyn">
11021148
<title>Executing Dynamic Commands</title>
11031149

@@ -1129,7 +1175,7 @@ EXECUTE <replaceable class="command">command-string</replaceable>;
11291175
<para>
11301176
When working with dynamic commands you will often have to handle escaping
11311177
of single quotes. The recommended method for quoting fixed text in your
1132-
function body is dollar quoting. If you have legacy codewhich does
1178+
function body is dollar quoting. If you have legacy codethat does
11331179
not use dollar quoting, please refer to the
11341180
overview in <xref linkend="plpgsql-quote-tips">, which can save you
11351181
some effort when translating said code to a more reasonable scheme.
@@ -1158,14 +1204,15 @@ EXECUTE <replaceable class="command">command-string</replaceable>;
11581204
</para>
11591205

11601206
<para>
1161-
An example (this assumes that you are using dollar quoting, so the
1162-
quote marks need not be doubled):
1207+
An example (this assumes that you are using dollar quoting for the
1208+
function as a whole, so thequote marks need not be doubled):
11631209
<programlisting>
11641210
EXECUTE 'UPDATE tbl SET '
11651211
|| quote_ident(colname)
11661212
|| ' = '
11671213
|| quote_literal(newvalue)
1168-
|| ' WHERE ...';
1214+
|| ' WHERE key = '
1215+
|| quote_literal(keyvalue);
11691216
</programlisting>
11701217
</para>
11711218

@@ -1193,7 +1240,8 @@ EXECUTE 'UPDATE tbl SET '
11931240
|| quote_ident(colname)
11941241
|| ' = $$'
11951242
|| newvalue
1196-
|| '$$ WHERE ...';
1243+
|| '$$ WHERE key = '
1244+
|| quote_literal(keyvalue);
11971245
</programlisting>
11981246
because it would break if the contents of <literal>newvalue</>
11991247
happened to contain <literal>$$</>. The same objection would

‎src/pl/plpgsql/src/gram.y

Lines changed: 23 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
* procedural language
55
*
66
* IDENTIFICATION
7-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.59 2004/07/31 23:04:56 tgl Exp $
7+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.60 2004/08/16 17:52:06 tgl Exp $
88
*
99
* This software is copyrighted by Jan Wieck - Hamburg.
1010
*
@@ -132,7 +132,7 @@ staticvoid check_assignable(PLpgSQL_datum *datum);
132132
%type<stmt>stmt_returnstmt_return_nextstmt_raisestmt_execsql
133133
%type<stmt>stmt_forstmt_selectstmt_perform
134134
%type<stmt>stmt_dynexecutestmt_getdiag
135-
%type<stmt>stmt_openstmt_fetchstmt_close
135+
%type<stmt>stmt_openstmt_fetchstmt_closestmt_null
136136

137137
%type<exceptions>exception_sectproc_exceptions
138138
%type<exception>proc_exception
@@ -592,29 +592,31 @@ proc_sect:
592592

593593
proc_stmts:proc_stmtsproc_stmt
594594
{
595+
if ($2 !=NULL)
596+
{
595597
if ($1->stmts_used ==$1->stmts_alloc)
596598
{
597599
$1->stmts_alloc *=2;
598600
$1->stmts = realloc($1->stmts,sizeof(PLpgSQL_stmt *) *$1->stmts_alloc);
599601
}
600602
$1->stmts[$1->stmts_used++] =$2;
601-
602-
$$ =$1;
603+
}
604+
$$ =$1;
603605
}
604606
|proc_stmt
605607
{
606-
PLpgSQL_stmts*new;
608+
PLpgSQL_stmts*new;
607609

608-
new = malloc(sizeof(PLpgSQL_stmts));
609-
memset(new,0,sizeof(PLpgSQL_stmts));
610+
new = malloc(sizeof(PLpgSQL_stmts));
611+
memset(new,0,sizeof(PLpgSQL_stmts));
610612

611-
new->stmts_alloc =64;
612-
new->stmts_used =1;
613-
new->stmts = malloc(sizeof(PLpgSQL_stmt *) *new->stmts_alloc);
614-
new->stmts[0] =$1;
613+
new->stmts_alloc =32;
614+
new->stmts = malloc(sizeof(PLpgSQL_stmt *) *new->stmts_alloc);
615615

616-
$$ =new;
616+
if ($1 !=NULL)
617+
new->stmts[new->stmts_used++] =$1;
617618

619+
$$ =new;
618620
}
619621
;
620622

@@ -654,6 +656,8 @@ proc_stmt: pl_block ';'
654656
{$$ =$1; }
655657
|stmt_close
656658
{$$ =$1; }
659+
|stmt_null
660+
{$$ =$1; }
657661
;
658662

659663
stmt_perform:K_PERFORMlnoexpr_until_semi
@@ -1493,6 +1497,13 @@ stmt_close: K_CLOSE lno cursor_variable ';'
14931497
}
14941498
;
14951499

1500+
stmt_null:K_NULL';'
1501+
{
1502+
/* We do not bother building a node for NULL*/
1503+
$$ =NULL;
1504+
}
1505+
;
1506+
14961507
cursor_varptr:T_SCALAR
14971508
{
14981509
if (yylval.scalar->dtype != PLPGSQL_DTYPE_VAR)

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