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Code review for UPDATE SET (columnlist) patch. Make it handle as much
of the syntax as this fundamentally dead-end approach can, in particular combinations of single and multi column assignments. Improve rather inadequate documentation and provide some regression tests.
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+195
-141
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4 files changed

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-141
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‎doc/src/sgml/ref/update.sgml

Lines changed: 24 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.39 2006/09/02 20:34:47 momjian Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.40 2006/09/03 22:37:05 tgl Exp $
33
PostgreSQL documentation
44
-->
55

@@ -21,8 +21,8 @@ PostgreSQL documentation
2121
<refsynopsisdiv>
2222
<synopsis>
2323
UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> ]
24-
[ SET <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] |
25-
SET ( <replaceable class="PARAMETER">column</replaceable> [, ...] ) = ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) [, ...] ]
24+
SET { <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } |
25+
( <replaceable class="PARAMETER">column</replaceable> [, ...] ) = ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) } [, ...]
2626
[ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
2727
[ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
2828
[ RETURNING * | <replaceable class="parameter">output_expression</replaceable> [ AS <replaceable class="parameter">output_name</replaceable> ] [, ...] ]
@@ -251,10 +251,6 @@ UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama';
251251
<programlisting>
252252
UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
253253
WHERE city = 'San Francisco' AND date = '2003-07-03';
254-
</programlisting>
255-
<programlisting>
256-
UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
257-
WHERE city = 'San Francisco' AND date = '2003-07-03';
258254
</programlisting>
259255
</para>
260256

@@ -268,6 +264,14 @@ UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
268264
</programlisting>
269265
</para>
270266

267+
<para>
268+
Use the alternative column-list syntax to do the same update:
269+
<programlisting>
270+
UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
271+
WHERE city = 'San Francisco' AND date = '2003-07-03';
272+
</programlisting>
273+
</para>
274+
271275
<para>
272276
Increment the sales count of the salesperson who manages the
273277
account for Acme Corporation, using the <literal>FROM</literal>
@@ -316,6 +320,19 @@ COMMIT;
316320
are <productname>PostgreSQL</productname> extensions.
317321
</para>
318322

323+
<para>
324+
According to the standard, the column-list syntax should allow a list
325+
of columns to be assigned from a single row-valued expression, such
326+
as a sub-select:
327+
<programlisting>
328+
UPDATE accounts SET (contact_last_name, contact_first_name) =
329+
(SELECT last_name, first_name FROM salesmen
330+
WHERE salesmen.id = accounts.sales_id);
331+
</programlisting>
332+
This is not currently implemented &mdash; the source must be a list
333+
of independent expressions.
334+
</para>
335+
319336
<para>
320337
Some other database systems offer a <literal>FROM</> option in which
321338
the target table is supposed to be listed again within <literal>FROM</>.

‎src/backend/parser/gram.y

Lines changed: 96 additions & 104 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
*
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.564 2006/09/03 03:19:44 momjian Exp $
14+
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.565 2006/09/03 22:37:05 tgl Exp $
1515
*
1616
* HISTORY
1717
* AUTHOR DATE MAJOR EVENT
@@ -236,9 +236,9 @@ static void doNegateFloat(Value *v);
236236
name_list from_clause from_list opt_array_bounds
237237
qualified_name_list any_name any_name_list
238238
any_operator expr_list attrs
239-
target_list update_col_list update_target_list
240-
update_value_list set_opt insert_column_list
241-
values_list def_list indirection opt_indirection
239+
target_list insert_column_list set_target_list
240+
set_clause_list set_clause multiple_set_clause
241+
ctext_expr_list ctext_row def_list indirection opt_indirection
242242
group_clause TriggerFuncArgs select_limit
243243
opt_select_limit opclass_item_list
244244
transaction_mode_list_or_empty
@@ -299,7 +299,7 @@ static void doNegateFloat(Value *v);
299299
%type <list> when_clause_list
300300
%type <ival> sub_type
301301
%type <list> OptCreateAs CreateAsList
302-
%type <node> CreateAsElement values_item
302+
%type <node> CreateAsElement ctext_expr
303303
%type <value> NumericOnly FloatOnly IntegerOnly
304304
%type <alias> alias_clause
305305
%type <sortby> sortby
@@ -308,8 +308,7 @@ static void doNegateFloat(Value *v);
308308
%type <jexpr> joined_table
309309
%type <range> relation_expr
310310
%type <range> relation_expr_opt_alias
311-
%type <target> target_el update_target_el update_col_list_el insert_column_item
312-
%type <list> update_target_lists_list update_target_lists_el
311+
%type <target> target_el single_set_clause set_target insert_column_item
313312

314313
%type <typnam> Typename SimpleTypename ConstTypename
315314
GenericType Numeric opt_float
@@ -5488,7 +5487,7 @@ opt_nowait: NOWAIT { $$ = TRUE; }
54885487
*****************************************************************************/
54895488

54905489
UpdateStmt: UPDATE relation_expr_opt_alias
5491-
SET set_opt
5490+
SET set_clause_list
54925491
from_clause
54935492
where_clause
54945493
returning_clause
@@ -5503,9 +5502,65 @@ UpdateStmt: UPDATE relation_expr_opt_alias
55035502
}
55045503
;
55055504

5506-
set_opt:
5507-
update_target_list { $$ = $1; }
5508-
| update_target_lists_list { $$ = $1; }
5505+
set_clause_list:
5506+
set_clause { $$ = $1; }
5507+
| set_clause_list ',' set_clause { $$ = list_concat($1,$3); }
5508+
;
5509+
5510+
set_clause:
5511+
single_set_clause { $$ = list_make1($1); }
5512+
| multiple_set_clause { $$ = $1; }
5513+
;
5514+
5515+
single_set_clause:
5516+
set_target '=' ctext_expr
5517+
{
5518+
$$ = $1;
5519+
$$->val = (Node *) $3;
5520+
}
5521+
;
5522+
5523+
multiple_set_clause:
5524+
'(' set_target_list ')' '=' ctext_row
5525+
{
5526+
ListCell *col_cell;
5527+
ListCell *val_cell;
5528+
5529+
/*
5530+
* Break the ctext_row apart, merge individual expressions
5531+
* into the destination ResTargets. XXX this approach
5532+
* cannot work for general row expressions as sources.
5533+
*/
5534+
if (list_length($2) != list_length($5))
5535+
ereport(ERROR,
5536+
(errcode(ERRCODE_SYNTAX_ERROR),
5537+
errmsg("number of columns does not match number of values")));
5538+
forboth(col_cell, $2, val_cell, $5)
5539+
{
5540+
ResTarget *res_col = (ResTarget *) lfirst(col_cell);
5541+
Node *res_val = (Node *) lfirst(val_cell);
5542+
5543+
res_col->val = res_val;
5544+
}
5545+
5546+
$$ = $2;
5547+
}
5548+
;
5549+
5550+
set_target:
5551+
ColId opt_indirection
5552+
{
5553+
$$ = makeNode(ResTarget);
5554+
$$->name = $1;
5555+
$$->indirection = $2;
5556+
$$->val = NULL; /* upper production sets this */
5557+
$$->location = @1;
5558+
}
5559+
;
5560+
5561+
set_target_list:
5562+
set_target { $$ = list_make1($1); }
5563+
| set_target_list ',' set_target { $$ = lappend($1,$3); }
55095564
;
55105565

55115566

@@ -5887,83 +5942,20 @@ locked_rels_list:
58875942

58885943

58895944
values_clause:
5890-
VALUES '(' values_list ')'
5945+
VALUES ctext_row
58915946
{
58925947
SelectStmt *n = makeNode(SelectStmt);
5893-
n->valuesLists = list_make1($3);
5948+
n->valuesLists = list_make1($2);
58945949
$$ = (Node *) n;
58955950
}
5896-
| values_clause ',' '(' values_list ')'
5951+
| values_clause ',' ctext_row
58975952
{
58985953
SelectStmt *n = (SelectStmt *) $1;
5899-
n->valuesLists = lappend(n->valuesLists, $4);
5954+
n->valuesLists = lappend(n->valuesLists, $3);
59005955
$$ = (Node *) n;
59015956
}
59025957
;
59035958

5904-
values_list: values_item { $$ = list_make1($1); }
5905-
| values_list ',' values_item { $$ = lappend($1, $3); }
5906-
;
5907-
5908-
values_item:
5909-
a_expr { $$ = (Node *) $1; }
5910-
| DEFAULT { $$ = (Node *) makeNode(SetToDefault); }
5911-
;
5912-
5913-
update_target_lists_list:
5914-
update_target_lists_el { $$ = $1; }
5915-
| update_target_lists_list ',' update_target_lists_el { $$ = list_concat($1, $3); }
5916-
;
5917-
5918-
update_target_lists_el:
5919-
'(' update_col_list ')' '=' '(' update_value_list ')'
5920-
{
5921-
ListCell *col_cell;
5922-
ListCell *val_cell;
5923-
5924-
if (list_length($2) != list_length($6))
5925-
{
5926-
ereport(ERROR,
5927-
(errcode(ERRCODE_SYNTAX_ERROR),
5928-
errmsg("number of columns does not match to number of values")));
5929-
}
5930-
5931-
for (col_cell = list_head($2), val_cell = list_head($6);
5932-
col_cell != NULL && val_cell != NULL;
5933-
col_cell = lnext(col_cell), val_cell = lnext(val_cell))
5934-
{
5935-
/* merge update_value_list with update_col_list */
5936-
ResTarget *res_col = (ResTarget *) lfirst(col_cell);
5937-
Node *res_val = (Node *) lfirst(val_cell);
5938-
5939-
res_col->val = res_val;
5940-
}
5941-
5942-
$$ = $2;
5943-
}
5944-
;
5945-
5946-
update_col_list:
5947-
update_col_list_el { $$ = list_make1($1); }
5948-
| update_col_list ',' update_col_list_el { $$ = lappend($1, $3); }
5949-
;
5950-
5951-
update_col_list_el:
5952-
ColId opt_indirection
5953-
{
5954-
$$ = makeNode(ResTarget);
5955-
$$->name = $1;
5956-
$$->indirection = $2;
5957-
$$->val = NULL;
5958-
$$->location = @1;
5959-
}
5960-
;
5961-
5962-
update_value_list:
5963-
values_item { $$ = list_make1($1); }
5964-
| update_value_list ',' values_item { $$ = lappend($1, $3); }
5965-
;
5966-
59675959

59685960
/*****************************************************************************
59695961
*
@@ -8232,10 +8224,35 @@ opt_asymmetric: ASYMMETRIC
82328224
| /*EMPTY*/
82338225
;
82348226

8227+
/*
8228+
* The SQL spec defines "contextually typed value expressions" and
8229+
* "contextually typed row value constructors", which for our purposes
8230+
* are the same as "a_expr" and "row" except that DEFAULT can appear at
8231+
* the top level.
8232+
*/
8233+
8234+
ctext_expr:
8235+
a_expr { $$ = (Node *) $1; }
8236+
| DEFAULT { $$ = (Node *) makeNode(SetToDefault); }
8237+
;
8238+
8239+
ctext_expr_list:
8240+
ctext_expr { $$ = list_make1($1); }
8241+
| ctext_expr_list ',' ctext_expr { $$ = lappend($1, $3); }
8242+
;
8243+
8244+
/*
8245+
* We should allow ROW '(' ctext_expr_list ')' too, but that seems to require
8246+
* making VALUES a fully reserved word, which will probably break more apps
8247+
* than allowing the noise-word is worth.
8248+
*/
8249+
ctext_row: '(' ctext_expr_list ')' { $$ = $2; }
8250+
;
8251+
82358252

82368253
/*****************************************************************************
82378254
*
8238-
* target lists for SELECT, UPDATE, INSERT
8255+
* target list for SELECT
82398256
*
82408257
*****************************************************************************/
82418258

@@ -8275,31 +8292,6 @@ target_el: a_expr AS ColLabel
82758292
}
82768293
;
82778294

8278-
update_target_list:
8279-
update_target_el { $$ = list_make1($1); }
8280-
| update_target_list ',' update_target_el { $$ = lappend($1,$3); }
8281-
;
8282-
8283-
update_target_el:
8284-
ColId opt_indirection '=' a_expr
8285-
{
8286-
$$ = makeNode(ResTarget);
8287-
$$->name = $1;
8288-
$$->indirection = $2;
8289-
$$->val = (Node *) $4;
8290-
$$->location = @1;
8291-
}
8292-
| ColId opt_indirection '=' DEFAULT
8293-
{
8294-
$$ = makeNode(ResTarget);
8295-
$$->name = $1;
8296-
$$->indirection = $2;
8297-
$$->val = (Node *) makeNode(SetToDefault);
8298-
$$->location = @1;
8299-
}
8300-
8301-
;
8302-
83038295

83048296
/*****************************************************************************
83058297
*

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