Add string_agg aggregate functions. The one argument version concatenates

the input values into a string. The two argument version also does the same
thing, but inserts delimiters between elements.

Original patch by Pavel Stehule, reviewed by David E. Wheeler and me.

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index f777f9f16503831831880fe340c27867ea3bf440..bd1bf35220683f5cceb49ce372ca8cb2237c3576 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.498 2010/01/25 20:55:32 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.499 2010/02/01 03:14:43 itagaki Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -1789,6 +1789,10 @@
     </tgroup>
    </table>
 
+   <para>
+   See also <xref linkend="functions-aggregate"> about the aggregate
+   function <function>string_agg</function>.
+   </para>
 
    <table id="conversion-names">
     <title>Built-in Conversions</title>
@@ -9836,6 +9840,25 @@ SELECT NULLIF(value, '(none)') ...
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <indexterm>
+        <primary>string_agg</primary>
+       </indexterm>
+       <function>
+         string_agg(<replaceable class="parameter">expression</replaceable> 
+                    [, <replaceable class="parameter">delimiter</replaceable> ] )
+       </function>
+      </entry>
+      <entry>
+       <type>text</type>
+      </entry>
+      <entry>
+       <type>text</type>
+      </entry>
+      <entry>input values concatenated into a string, optionally with delimiters</entry>
+     </row>
+
      <row>
       <entry><function>sum(<replaceable class="parameter">expression</replaceable>)</function></entry>
       <entry>

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 7a8abf14a83d11ae57fe46bcaa419271c6a2ae23..096ca75bf9362570eb07c1b25b3c0ea89534a759 100644 (file)
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.174 2010/01/25 20:55:32 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.175 2010/02/01 03:14:43 itagaki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 #include "libpq/md5.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
+#include "nodes/execnodes.h"
 #include "parser/scansup.h"
 #include "regex/regex.h"
 #include "utils/builtins.h"
@@ -73,6 +74,7 @@ static bytea *bytea_substring(Datum str,
                                int L,
                                bool length_not_specified);
 static bytea *bytea_overlay(bytea *t1, bytea *t2, int sp, int sl);
+static StringInfo makeStringAggState(fmNodePtr context);
 
 
 /*****************************************************************************
@@ -3315,3 +3317,105 @@ pg_column_size(PG_FUNCTION_ARGS)
 
        PG_RETURN_INT32(result);
 }
+
+/*
+ * string_agg - Concatenates values and returns string.
+ *
+ * Syntax: string_agg(value text, delimiter text = '') RETURNS text
+ *
+ * Note: Any NULL values are ignored. The first-call delimiter isn't
+ * actually used at all, and on subsequent calls the delimiter precedes
+ * the associated value.
+ */
+static StringInfo
+makeStringAggState(fmNodePtr context)
+{
+       StringInfo              state;
+       MemoryContext   aggcontext;
+       MemoryContext   oldcontext;
+
+       if (context && IsA(context, AggState))
+               aggcontext = ((AggState *) context)->aggcontext;
+       else if (context && IsA(context, WindowAggState))
+               aggcontext = ((WindowAggState *) context)->wincontext;
+       else
+       {
+               /* cannot be called directly because of internal-type argument */
+               elog(ERROR, "string_agg_transfn called in non-aggregate context");
+               aggcontext = NULL;              /* keep compiler quiet */
+       }
+
+       /* Create state in aggregate context */
+       oldcontext = MemoryContextSwitchTo(aggcontext);
+       state = makeStringInfo();
+       MemoryContextSwitchTo(oldcontext);
+
+       return state;
+}
+
+Datum
+string_agg_transfn(PG_FUNCTION_ARGS)
+{
+       StringInfo              state;
+
+       state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
+
+       /* Append the element unless not null. */
+       if (!PG_ARGISNULL(1))
+       {
+               if (state == NULL)
+                       state = makeStringAggState(fcinfo->context);
+               appendStringInfoText(state, PG_GETARG_TEXT_PP(1));      /* value */
+       }
+
+       /*
+        * The transition type for string_agg() is declared to be "internal", which
+        * is a pass-by-value type the same size as a pointer.  
+        */
+       PG_RETURN_POINTER(state);
+}
+
+Datum 
+string_agg_delim_transfn(PG_FUNCTION_ARGS)
+{
+       StringInfo              state;
+
+       state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
+
+       /* Append the value unless not null. */
+       if (!PG_ARGISNULL(1))
+       {
+               if (state == NULL)
+                       state = makeStringAggState(fcinfo->context);
+               else if (!PG_ARGISNULL(2))
+                       appendStringInfoText(state, PG_GETARG_TEXT_PP(2));      /* delimiter */
+
+               appendStringInfoText(state, PG_GETARG_TEXT_PP(1));      /* value */
+       }
+
+       /*
+        * The transition type for string_agg() is declared to be "internal", which
+        * is a pass-by-value type the same size as a pointer.
+        */
+       PG_RETURN_POINTER(state);
+}
+
+Datum
+string_agg_finalfn(PG_FUNCTION_ARGS)
+{
+       StringInfo              state;
+
+       if (PG_ARGISNULL(0))
+               PG_RETURN_NULL();
+
+       /* cannot be called directly because of internal-type argument */
+       Assert(fcinfo->context &&
+                  (IsA(fcinfo->context, AggState) ||
+                       IsA(fcinfo->context, WindowAggState)));
+
+       state = (StringInfo) PG_GETARG_POINTER(0);
+       if (state != NULL)
+               PG_RETURN_TEXT_P(cstring_to_text(state->data));
+       else
+               PG_RETURN_NULL();
+}

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 192f870b81ac21b9ea70e5949377ca3834f4fd59..e12ec58ed695b0a7568d22e08dcd811b2611edfd 100644 (file)
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.581 2010/01/28 23:21:12 petere Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.582 2010/02/01 03:14:43 itagaki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*                                                     yyyymmddN */
-#define CATALOG_VERSION_NO     201001282
+#define CATALOG_VERSION_NO     201002011
 
 #endif

diff --git a/src/include/catalog/pg_aggregate.h b/src/include/catalog/pg_aggregate.h
index 88b783fcc322f3978f052ca3877fa6b904101927..c47adbe4755c1f807287249fad07b153e58cb473 100644 (file)
--- a/src/include/catalog/pg_aggregate.h
+++ b/src/include/catalog/pg_aggregate.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_aggregate.h,v 1.70 2010/01/05 01:06:56 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_aggregate.h,v 1.71 2010/02/01 03:14:43 itagaki Exp $
  *
  * NOTES
  *       the genbki.pl script reads this file and generates .bki
@@ -223,6 +223,10 @@ DATA(insert ( 2901 xmlconcat2        -                                     0       142             _null_ ));
 /* array */
 DATA(insert ( 2335     array_agg_transfn       array_agg_finalfn               0       2281    _null_ ));
 
+/* text */
+DATA(insert (3537      string_agg_transfn                      string_agg_finalfn      0       2281    _null_ ));
+DATA(insert (3538      string_agg_delim_transfn        string_agg_finalfn      0       2281    _null_ ));
+
 /*
  * prototypes for functions in pg_aggregate.c
  */

diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index a30e06975815b304291e1b765b2d549c8ea03e64..ec45367b4aeba5fe1b712c6feeae92dc2a79396d 100644 (file)
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.566 2010/01/28 14:25:41 mha Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.567 2010/02/01 03:14:44 itagaki Exp $
  *
  * NOTES
  *       The script catalog/genbki.pl reads this file and generates .bki
@@ -2829,6 +2829,16 @@ DATA(insert OID = 2816 (  float8_covar_samp                      PGNSP PGUID 12 1 0 0 f f f t f i 1
 DESCR("COVAR_SAMP(double, double) aggregate final function");
 DATA(insert OID = 2817 (  float8_corr                          PGNSP PGUID 12 1 0 0 f f f t f i 1 0 701 "1022" _null_ _null_ _null_ _null_ float8_corr _null_ _null_ _null_ ));
 DESCR("CORR(double, double) aggregate final function");
+DATA(insert OID = 3534 (  string_agg_transfn           PGNSP PGUID 12 1 0 0 f f f f f i 2 0 2281 "2281 25" _null_ _null_ _null_ _null_ string_agg_transfn _null_ _null_ _null_ ));
+DESCR("string_agg(text) transition function");
+DATA(insert OID = 3535 (  string_agg_delim_transfn     PGNSP PGUID 12 1 0 0 f f f f f i 3 0 2281 "2281 25 25" _null_ _null_ _null_ _null_ string_agg_delim_transfn _null_ _null_ _null_ ));
+DESCR("string_agg(text, text) transition function");
+DATA(insert OID = 3536 (  string_agg_finalfn           PGNSP PGUID 12 1 0 0 f f f f f i 1 0 25 "2281" _null_ _null_ _null_ _null_ string_agg_finalfn _null_ _null_ _null_ ));
+DESCR("string_agg final function");
+DATA(insert OID = 3537 (  string_agg                           PGNSP PGUID 12 1 0 0 t f f f f i 1 0 25 "25" _null_ _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
+DESCR("concatenate aggregate input into an string");
+DATA(insert OID = 3538 (  string_agg                           PGNSP PGUID 12 1 0 0 t f f f f i 2 0 25 "25 25" _null_ _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
+DESCR("concatenate aggregate input into an string with delimiter");
 
 /* To ASCII conversion */
 DATA(insert OID = 1845 ( to_ascii      PGNSP PGUID 12 1 0 0 f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_        to_ascii_default _null_ _null_ _null_ ));

diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 11eb8acacc770e23cecf5be591843a8dab2fca9d..6381c3d735652e53b467833b24f9dfd03654cb1d 100644 (file)
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.345 2010/01/25 20:55:32 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.346 2010/02/01 03:14:45 itagaki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -724,6 +724,10 @@ extern Datum unknownsend(PG_FUNCTION_ARGS);
 
 extern Datum pg_column_size(PG_FUNCTION_ARGS);
 
+extern Datum string_agg_transfn(PG_FUNCTION_ARGS);
+extern Datum string_agg_delim_transfn(PG_FUNCTION_ARGS);
+extern Datum string_agg_finalfn(PG_FUNCTION_ARGS);
+
 /* version.c */
 extern Datum pgsql_version(PG_FUNCTION_ARGS);
 
@@ -772,6 +776,9 @@ extern Datum translate(PG_FUNCTION_ARGS);
 extern Datum chr (PG_FUNCTION_ARGS);
 extern Datum repeat(PG_FUNCTION_ARGS);
 extern Datum ascii(PG_FUNCTION_ARGS);
+extern Datum string_agg_transfn(PG_FUNCTION_ARGS);
+extern Datum string_agg_delim_transfn(PG_FUNCTION_ARGS);
+extern Datum string_agg_finalfn(PG_FUNCTION_ARGS);
 
 /* inet_net_ntop.c */
 extern char *inet_net_ntop(int af, const void *src, int bits,

diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 9669a52fbeaeb448aff76bb74a2d8a52075b0c49..2460d9dfd626ad493ec889527eba06f13cba5f39 100644 (file)
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -799,3 +799,34 @@ select aggfns(distinct a,a,c order by a,b)
 ERROR:  in an aggregate with DISTINCT, ORDER BY expressions must appear in argument list
 LINE 1: select aggfns(distinct a,a,c order by a,b)
                                                 ^
+-- string_agg tests
+select string_agg(a) from (values('aaaa'),('bbbb'),('cccc')) g(a);
+  string_agg  
+--------------
+ aaaabbbbcccc
+(1 row)
+
+select string_agg(a,',') from (values('aaaa'),('bbbb'),('cccc')) g(a);
+   string_agg   
+----------------
+ aaaa,bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values('aaaa'),(null),('bbbb'),('cccc')) g(a);
+   string_agg   
+----------------
+ aaaa,bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values(null),(null),('bbbb'),('cccc')) g(a);
+ string_agg 
+------------
+ bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values(null),(null)) g(a);
+ string_agg 
+------------
+ 
+(1 row)
+

diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index 18f2e57b72b7fadc3895f87e8025a9fc66d2ad54..daa89167a20f43fbca5165e6d14143c8168e634a 100644 (file)
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -355,3 +355,10 @@ select aggfns(distinct a,b,c order by a,b,i,c)
   from (values (1,1,'foo')) v(a,b,c), generate_series(1,2) i;
 select aggfns(distinct a,a,c order by a,b)
   from (values (1,1,'foo')) v(a,b,c), generate_series(1,2) i;
+
+-- string_agg tests
+select string_agg(a) from (values('aaaa'),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values('aaaa'),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values('aaaa'),(null),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values(null),(null),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values(null),(null)) g(a);