Add support for custom hypertable dimension types

Previously, if a hypertable dimension type did not have a default
hash function, create_hypertable would throw an error.
However, this should not be the case if a custom partitioning
function is provided.
This commit addresses the issue making sure that arbitrary
custom types can be used as partitioning dimensions as long
as a valid partitioning function is provided.
Fixes #470.

src/partitioning.c

@@ -92,6 +92,13 @@ partitioning_func_get_default(void)
 								 DEFAULT_PARTITIONING_FUNC_NAME);
 }
 
+bool
+partitioning_func_is_default(const char *schema, const char *funcname)
+{
+	return strcmp(DEFAULT_PARTITIONING_FUNC_SCHEMA, schema) == 0 &&
+		strcmp(DEFAULT_PARTITIONING_FUNC_NAME, funcname) == 0;
+}
+
 /*
  * Resolve the partitioning function set for a hypertable.
  */
@@ -166,8 +173,8 @@ partitioning_info_create(const char *schema,
 	columntype = get_atttype(relid, pinfo->column_attnum);
 	tce = lookup_type_cache(columntype, TYPECACHE_HASH_FLAGS);
 
-	if (tce->hash_proc == InvalidOid)
+	if (tce->hash_proc == InvalidOid && partitioning_func_is_default(schema, partfunc))
-		elog(ERROR, "could not find hash function for type %u", columntype);
+		elog(ERROR, "could not find hash function for type %s", format_type_be(columntype));
 
 	partitioning_func_set_func_fmgr(&pinfo->partfunc);
 

src/partitioning.h

@@ -39,6 +39,7 @@ typedef struct PartitioningInfo
 
 
 extern Oid	partitioning_func_get_default(void);
+extern bool partitioning_func_is_default(const char *schema, const char *funcname);
 extern bool partitioning_func_is_valid(regproc funcoid);
 
 extern PartitioningInfo *partitioning_info_create(const char *schema,

test/expected/partitioning.out

@@ -261,3 +261,31 @@ ERROR:  cannot create a unique index without the column "device" (used in partit
 \set ON_ERROR_STOP 1
 -- NON-unique indexes can still be created
 CREATE INDEX temp_index ON hyper_with_index(temp);
+-- Make sure custom composite types are supported as dimensions
+CREATE TYPE TUPLE as (val1 int4, val2 int4);
+CREATE FUNCTION tuple_hash(value ANYELEMENT) RETURNS INT4
+LANGUAGE PLPGSQL IMMUTABLE AS
+$BODY$
+BEGIN
+    RAISE NOTICE 'custom hash value is: %', value.val1+value.val2;
+    RETURN value.val1+value.val2;
+END
+$BODY$;
+CREATE TABLE part_custom_dim (time TIMESTAMPTZ, combo TUPLE, device TEXT);
+\set ON_ERROR_STOP 0
+-- should fail because no partitioning function supplied and the given custom type
+-- has no default hash function
+SELECT create_hypertable('part_custom_dim', 'time', 'combo', 4);
+NOTICE:  adding not-null constraint to column "time"
+ERROR:  could not find hash function for type tuple
+\set ON_ERROR_STOP 1
+SELECT create_hypertable('part_custom_dim', 'time', 'combo', 4, partitioning_func=>'tuple_hash');
+NOTICE:  adding not-null constraint to column "time"
+ create_hypertable 
+-------------------
+ 
+(1 row)
+
+INSERT INTO part_custom_dim(time, combo) VALUES (now(), (1,2));
+NOTICE:  custom hash value is: 3
+NOTICE:  custom hash value is: 3

test/sql/partitioning.sql

@@ -83,6 +83,7 @@ INSERT INTO part_custom_func VALUES ('2017-03-22T09:18:23', 23.4, 'dev1'),
                                     ('2017-03-22T09:18:23', 23.4, 'dev7');
 
 SELECT * FROM test.show_subtables('part_custom_func');
+
 -- Test that index creation is handled correctly.
 CREATE TABLE hyper_with_index(time timestamptz, temp float, device int);
 CREATE UNIQUE INDEX temp_index ON hyper_with_index(temp);
@@ -126,3 +127,25 @@ SELECT add_dimension('hyper_with_primary', 'device', 4);
 
 -- NON-unique indexes can still be created
 CREATE INDEX temp_index ON hyper_with_index(temp);
+
+-- Make sure custom composite types are supported as dimensions
+CREATE TYPE TUPLE as (val1 int4, val2 int4);
+CREATE FUNCTION tuple_hash(value ANYELEMENT) RETURNS INT4
+LANGUAGE PLPGSQL IMMUTABLE AS
+$BODY$
+BEGIN
+    RAISE NOTICE 'custom hash value is: %', value.val1+value.val2;
+    RETURN value.val1+value.val2;
+END
+$BODY$;
+
+CREATE TABLE part_custom_dim (time TIMESTAMPTZ, combo TUPLE, device TEXT);
+
+\set ON_ERROR_STOP 0
+-- should fail because no partitioning function supplied and the given custom type
+-- has no default hash function
+SELECT create_hypertable('part_custom_dim', 'time', 'combo', 4);
+\set ON_ERROR_STOP 1
+SELECT create_hypertable('part_custom_dim', 'time', 'combo', 4, partitioning_func=>'tuple_hash');
+
+INSERT INTO part_custom_dim(time, combo) VALUES (now(), (1,2));