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Add COLLATION FOR expression
reviewed by Jaime Casanova
1 parent d41f510 commit 6688d28

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9 files changed

+103
-3
lines changed

9 files changed

+103
-3
lines changed

‎doc/src/sgml/func.sgml

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Original file line numberDiff line numberDiff line change
@@ -13698,6 +13698,10 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
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<primary>pg_typeof</primary>
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</indexterm>
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<indexterm>
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<primary>collation for</primary>
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</indexterm>
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<para>
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<xref linkend="functions-info-catalog-table"> lists functions that
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extract information from the system catalogs.
@@ -13859,6 +13863,11 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
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<entry><type>regtype</type></entry>
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<entry>get the data type of any value</entry>
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</row>
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<row>
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<entry><literal><function>collation for (<parameter>any</parameter>)</function></literal></entry>
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<entry><type>text</type></entry>
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<entry>get the collation of the argument</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
@@ -13983,6 +13992,27 @@ SELECT typlen FROM pg_type WHERE oid = pg_typeof(33);
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4
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(1 row)
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</programlisting>
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</para>
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<para>
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The expression <literal>collation for</literal> returns the collation of the
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value that is passed to it. Example:
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<programlisting>
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SELECT collation for (description) FROM pg_description LIMIT 1;
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pg_collation_for
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------------------
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"default"
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(1 row)
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SELECT collation for ('foo' COLLATE "de_DE");
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pg_collation_for
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------------------
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"de_DE"
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(1 row)
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</programlisting>
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The value might be quoted and schema-qualified. If no collation is derived
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for the argument expression, then a null value is returned. If the argument
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is not of a collatable data type, then an error is raised.
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</para>
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<indexterm>

‎src/backend/parser/gram.y

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10701,6 +10701,19 @@ func_expr: func_name '(' ')' over_clause
1070110701
n->location = @1;
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$$ = (Node *)n;
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}
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| COLLATION FOR '(' a_expr ')'
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{
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FuncCall *n = makeNode(FuncCall);
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n->funcname = SystemFuncName("pg_collation_for");
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n->args = list_make1($4);
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n->agg_order = NIL;
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n->agg_star = FALSE;
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n->agg_distinct = FALSE;
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n->func_variadic = FALSE;
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n->over = NULL;
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n->location = @1;
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$$ = (Node *)n;
10716+
}
1070410717
| CURRENT_DATE
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{
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/*
@@ -12152,7 +12165,6 @@ unreserved_keyword:
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| CLASS
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| CLOSE
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| CLUSTER
12155-
| COLLATION
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| COMMENT
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| COMMENTS
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| COMMIT
@@ -12491,6 +12503,7 @@ reserved_keyword:
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| CAST
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| CHECK
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| COLLATE
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| COLLATION
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| COLUMN
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| CONSTRAINT
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| CREATE

‎src/backend/utils/adt/misc.c

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -32,6 +32,7 @@
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#include "storage/pmsignal.h"
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#include "storage/proc.h"
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#include "storage/procarray.h"
35+
#include "utils/lsyscache.h"
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#include "tcop/tcopprot.h"
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#include "utils/builtins.h"
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#include "utils/timestamp.h"
@@ -492,3 +493,29 @@ pg_typeof(PG_FUNCTION_ARGS)
492493
{
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PG_RETURN_OID(get_fn_expr_argtype(fcinfo->flinfo, 0));
494495
}
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/*
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* Implementation of the COLLATE FOR expression; returns the collation
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* of the argument.
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*/
502+
Datum
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pg_collation_for(PG_FUNCTION_ARGS)
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{
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Oid typeid;
506+
Oid collid;
507+
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typeid = get_fn_expr_argtype(fcinfo->flinfo, 0);
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if (!typeid)
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PG_RETURN_NULL();
511+
if (!type_is_collatable(typeid) && typeid != UNKNOWNOID)
512+
ereport(ERROR,
513+
(errcode(ERRCODE_DATATYPE_MISMATCH),
514+
errmsg("collations are not supported by type %s",
515+
format_type_be(typeid))));
516+
517+
collid = PG_GET_COLLATION();
518+
if (!collid)
519+
PG_RETURN_NULL();
520+
PG_RETURN_TEXT_P(cstring_to_text(generate_collation_name(collid)));
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}

‎src/include/catalog/catversion.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,6 @@
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*/
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5555
/* yyyymmddN */
56-
#define CATALOG_VERSION_NO 201203011
56+
#define CATALOG_VERSION_NO 201203021
5757

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#endif

‎src/include/catalog/pg_proc.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1953,6 +1953,8 @@ DESCR("convert generic options array to name/value table");
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DATA(insert OID = 1619 ( pg_typeof PGNSP PGUID 12 1 0 0 0 f f f f f f s 1 0 2206 "2276" _null_ _null_ _null_ _null_ pg_typeof _null_ _null_ _null_ ));
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DESCR("type of the argument");
1956+
DATA(insert OID = 3162 ( pg_collation_for PGNSP PGUID 12 1 0 0 0 f f f f f f s 1 0 25 "2276" _null_ _null_ _null_ _null_ pg_collation_for _null_ _null_ _null_ ));
1957+
DESCR("collation of the argument; implementation of the COLLATION FOR expression");
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19571959
/* Deferrable unique constraint trigger */
19581960
DATA(insert OID = 1250 ( unique_key_recheck PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 2279 "" _null_ _null_ _null_ _null_ unique_key_recheck _null_ _null_ _null_ ));

‎src/include/parser/kwlist.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -79,7 +79,7 @@ PG_KEYWORD("close", CLOSE, UNRESERVED_KEYWORD)
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PG_KEYWORD("cluster", CLUSTER, UNRESERVED_KEYWORD)
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PG_KEYWORD("coalesce", COALESCE, COL_NAME_KEYWORD)
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PG_KEYWORD("collate", COLLATE, RESERVED_KEYWORD)
82-
PG_KEYWORD("collation", COLLATION, UNRESERVED_KEYWORD)
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PG_KEYWORD("collation", COLLATION, RESERVED_KEYWORD)
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PG_KEYWORD("column", COLUMN, RESERVED_KEYWORD)
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PG_KEYWORD("comment", COMMENT, UNRESERVED_KEYWORD)
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PG_KEYWORD("comments", COMMENTS, UNRESERVED_KEYWORD)

‎src/include/utils/builtins.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -480,6 +480,7 @@ extern Datum pg_rotate_logfile(PG_FUNCTION_ARGS);
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extern Datum pg_sleep(PG_FUNCTION_ARGS);
481481
extern Datum pg_get_keywords(PG_FUNCTION_ARGS);
482482
extern Datum pg_typeof(PG_FUNCTION_ARGS);
483+
extern Datum pg_collation_for(PG_FUNCTION_ARGS);
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484485
/* oid.c */
485486
extern Datum oidin(PG_FUNCTION_ARGS);

‎src/test/regress/expected/collate.out

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -577,6 +577,26 @@ RESET enable_nestloop;
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-- 9.1 bug with useless COLLATE in an expression subject to length coercion
578578
CREATE TEMP TABLE vctable (f1 varchar(25));
579579
INSERT INTO vctable VALUES ('foo' COLLATE "C");
580+
SELECT collation for ('foo'); -- unknown type - null
581+
pg_collation_for
582+
------------------
583+
584+
(1 row)
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586+
SELECT collation for ('foo'::text);
587+
pg_collation_for
588+
------------------
589+
"default"
590+
(1 row)
591+
592+
SELECT collation for ((SELECT a FROM collate_test1 LIMIT 1)); -- non-collatable type - error
593+
ERROR: collations are not supported by type integer
594+
SELECT collation for ((SELECT b FROM collate_test1 LIMIT 1));
595+
pg_collation_for
596+
------------------
597+
"C"
598+
(1 row)
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580600
--
581601
-- Clean up. Many of these table names will be re-used if the user is
582602
-- trying to run any platform-specific collation tests later, so we

‎src/test/regress/sql/collate.sql

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -219,6 +219,13 @@ RESET enable_nestloop;
219219
CREATE TEMP TABLE vctable (f1 varchar(25));
220220
INSERT INTO vctable VALUES ('foo' COLLATE "C");
221221

222+
223+
SELECT collation for ('foo'); -- unknown type - null
224+
SELECT collation for ('foo'::text);
225+
SELECT collation for ((SELECT a FROM collate_test1 LIMIT 1)); -- non-collatable type - error
226+
SELECT collation for ((SELECT b FROM collate_test1 LIMIT 1));
227+
228+
222229
--
223230
-- Clean up. Many of these table names will be re-used if the user is
224231
-- trying to run any platform-specific collation tests later, so we

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