Reallow conversions

For plain sequences and explict default value sequences.

Also, update to use the same naming convention for variables.

Makefile

@@ -16,7 +16,8 @@ DATA = snowflake--1.0.sql \
 	   snowflake--2.0--2.2.sql \
 	   snowflake--2.2.sql \
 	   snowflake--2.2--2.3.sql \
-	   snowflake--2.3.sql
+	   snowflake--2.3.sql \
+	   snowflake--2.3--2.4.sql
 PGFILEDESC = "snowflake - snowflake style IDs for PostgreSQL"
 
 REGRESS = conversion

expected/conversion.out

@@ -15,9 +15,14 @@ INSERT INTO t1 VALUES (DEFAULT);
 INSERT INTO t2 VALUES (DEFAULT);
 INSERT INTO t3 VALUES (DEFAULT);
 SELECT snowflake.convert_sequence_to_snowflake('t1'); -- ERROR, not a sequence
-ERROR:  Input value "public.t1" is not used by any relation as a DEFAULT value or an IDENTITY
+ERROR:  Input value "public.t1" is not a valid convertable sequence
 SELECT snowflake.convert_sequence_to_snowflake('seq_1'); -- ERROR, not assocoated with any relation
-ERROR:  Input value "public.seq_1" is not used by any relation as a DEFAULT value or an IDENTITY
+NOTICE:  ALTER SEQUENCE public.seq_1 NO CYCLE MAXVALUE 43
+ convert_sequence_to_snowflake 
+-------------------------------
+                             0
+(1 row)
+
 SELECT snowflake.convert_sequence_to_snowflake('t1_x_seq');
 NOTICE:  EXECUTE ALTER TABLE public.t1 ALTER COLUMN x SET DATA TYPE int8
 NOTICE:  EXECUTE ALTER TABLE public.t1 ALTER COLUMN x SET DEFAULT snowflake.nextval('public.t1_x_seq'::regclass)
@@ -144,6 +149,33 @@ FROM t3 ORDER BY x;
  f                      | f                      | f
 (2 rows)
 
+-- Explict default
+CREATE SEQUENCE favorite_seq;
+CREATE TABLE t4 (x integer DEFAULT nextval('favorite_seq'::regclass));
+INSERT INTO t4 values (DEFAULT);
+SELECT * FROM t4;
+ x 
+---
+ 1
+(1 row)
+
+SELECT snowflake.convert_sequence_to_snowflake('favorite_seq');
+NOTICE:  EXECUTE ALTER TABLE public.t4 ALTER COLUMN x SET DATA TYPE int8
+NOTICE:  EXECUTE ALTER TABLE public.t4 ALTER COLUMN x SET DEFAULT snowflake.nextval('public.favorite_seq'::regclass)
+NOTICE:  ALTER SEQUENCE public.favorite_seq NO CYCLE MAXVALUE 2
+ convert_sequence_to_snowflake 
+-------------------------------
+                             2
+(1 row)
+
+INSERT INTO t4 values (DEFAULT);
+SELECT x <= 42 AS is_not_snowflake_value FROM t4 ORDER BY x;
+ is_not_snowflake_value 
+------------------------
+ t
+ f
+(2 rows)
+
 -- Cleanup
-DROP TABLE t1,t2,t3 CASCADE;
+DROP TABLE t1,t2,t3,t4 CASCADE;
 DROP EXTENSION snowflake;

snowflake--2.3--2.4.sql

@@ -0,0 +1,246 @@
+/* snowflake--2.3--2.4.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION snowflake UPDATE TO '2.4'" to load this file. \quit
+
+-- ----------------------------------------------------------------------
+-- convert_sequence_to_snowflake()
+--
+-- Convert a sequence to use snowflake's nextval() for the following cases:
+--  - Used in an IDENTITY constraint
+--  - Used as a generated sequence for Serial or Bigserial
+--  - Used with nextval() as a default value
+--  - A plain sequence
+--
+-- Returns the number of changes done, including column default changes,
+-- and data type changes, such as changing to int8. The number does not
+-- include changing the sequence itself.
+--
+-- NOTES:
+-- 1. Changes the data type of affected columns to bigint.
+-- 2. IDENTITY ALWAYS restriction will be eased to DEFAULT.
+-- ----------------------------------------------------------------------
+CREATE OR REPLACE FUNCTION snowflake.convert_sequence_to_snowflake(p_seqid regclass)
+RETURNS integer
+SET search_path = pg_catalog
+AS $$
+DECLARE
+	v_objdesc			record; -- contains target (reloid,attnum) value
+	v_identdesc		record; -- sequence-related flags (attisidentity)
+	v_attrdef		record;
+	v_attr			record;
+	v_seq			record;
+	v_cmd			text;
+	v_num_altered	integer := 0;
+	v_last_value	bigint;
+	v_seqname1		text;
+	v_extseqname		text;
+	v_is_serial_def	boolean;
+	v_textstr			text;
+BEGIN
+	-- Identify the (relation,attnum) that uses this sequence as a source
+	-- for values. Follow the logic of the getOwnedSequences_internal.
+	--
+	-- Complain, if such data wasn't found - incoming object may be not
+	-- a sequence, or sequence which is used for different purposes.
+	-- v_objdesc's fields:
+	-- heapreloid - Oid of the target relation.
+	-- nspname - namespace of the sequence
+	-- seqname - sequence name
+	-- attnum - number of relation's attribute that employs this sequence
+	SELECT INTO v_objdesc
+		refobjid AS heapreloid,
+		c.relnamespace::regnamespace::text AS nspname,
+		c.relname AS seqname,
+		refobjsubid AS attnum,
+		deptype
+	FROM pg_depend AS d JOIN pg_class AS c ON (d.objid = c.oid)
+	WHERE
+		classid = 'pg_class'::regclass AND
+		deptype IN ('a','i','n') AND
+		c.oid = p_seqid AND relkind = 'S'
+	ORDER BY deptype; -- prioritize (a)uto and (i)nternal before (n)ormal
+
+	IF (v_objdesc IS NULL) THEN
+		raise EXCEPTION 'Input value "%" is not a valid convertable sequence', p_seqid;
+		RETURN false;
+	END IF;
+
+	-- ----
+	-- We are looking for column defaults that use the requested
+	-- sequence and the function nextval(). Because pg_get_expr()
+	-- omits the schemaname of the sequence if it is "public" we
+	-- need to be prepared for a schema qualified and unqualified
+	-- name here.
+	-- ----
+	SELECT INTO v_seqname1
+		quote_ident(v_objdesc.seqname);
+	SELECT INTO v_extseqname
+		quote_ident(v_objdesc.nspname) || '.' || quote_ident(v_objdesc.seqname);
+
+	IF v_objdesc.deptype IN ('a','i') THEN
+		-- Handle IDENTITY case and SERIAL/BIGSERIAL case
+
+		SELECT INTO v_identdesc
+			(attidentity = 'a' OR attidentity = 'd') AS is_identity,
+			c.relnamespace::regnamespace::text AS nspname,
+			c.relname AS relname,
+			a.attname AS attname
+		FROM pg_attribute a JOIN pg_class c ON (c.oid = a.attrelid)
+		WHERE a.attrelid = v_objdesc.heapreloid AND a.attnum = v_objdesc.attnum;
+
+		IF (v_identdesc.is_identity) THEN
+			UPDATE pg_attribute SET attidentity = ''
+			WHERE attrelid = v_objdesc.heapreloid AND attnum = v_objdesc.attnum;
+			RAISE NOTICE
+				'Update pg_attribute: reset attidentity value for table %, column %',
+				v_objdesc.heapreloid::regclass, v_identdesc.attname;
+		ELSE
+
+			-- Extract DEFAULT definition for the column and conver it into
+			-- a readable string representation.
+			SELECT INTO v_textstr
+				pg_get_expr(ad.adbin, ad.adrelid, true)
+			FROM pg_attrdef ad
+			WHERE adrelid = v_objdesc.heapreloid AND adnum = v_objdesc.attnum;
+
+			-- Check that the DEFAULT expression contains input sequence in a form
+			-- as related to the serial and bigserial type.
+			SELECT INTO v_is_serial_def
+			CASE WHEN
+					v_textstr = 'nextval(' || quote_literal(v_seqname1) || '::regclass)' OR
+					v_textstr = 'nextval(' || quote_literal(v_extseqname) || '::regclass)'
+			THEN true ELSE false END;
+
+			-- If there is another DEFAULT expression already set for this column, we
+			-- are not so bold to remove it, just complain,
+			IF (NOT v_is_serial_def) THEN
+				raise EXCEPTION
+					'definition of DEFAULT value for column "%" of relation "%" does not correspond serial or bigserial type: "%"',
+					v_identdesc.attname, v_identdesc.relname, v_textstr;
+			END IF;
+		END IF;
+
+		-- ----
+		-- If the attribute type is not bigint, we change it
+		-- ----
+		v_num_altered =
+			snowflake.convert_column_to_int8(v_objdesc.heapreloid::regclass,
+										 v_objdesc.attnum::smallint);
+
+		-- ----
+		-- Now we can change the default to snowflake.nextval()
+		-- ----
+		v_cmd = 'ALTER TABLE ' ||
+			quote_ident(v_identdesc.nspname) || '.' ||
+			quote_ident(v_identdesc.relname) ||
+			' ALTER COLUMN ' || quote_ident(v_identdesc.attname) ||
+			' SET DEFAULT snowflake.nextval(' ||
+			quote_literal(
+				quote_ident(v_objdesc.nspname) || '.' ||
+				quote_ident(v_objdesc.seqname)
+			) || '::regclass)';
+		RAISE NOTICE 'EXECUTE %', v_cmd;
+		EXECUTE v_cmd;
+	ELSE
+		-- Look for cases where the sequence is used as an explicit default value
+
+		FOR v_attrdef IN
+			WITH AD AS (
+				SELECT AD.*,
+					   pg_get_expr(AD.adbin, AD.adrelid, true) adstr
+				FROM pg_attrdef AD
+			)
+			SELECT * FROM AD
+			WHERE AD.adstr = 'nextval(' || quote_literal(v_seqname1) || '::regclass)'
+			   OR AD.adstr = 'nextval(' || quote_literal(v_extseqname) || '::regclass)'
+		LOOP
+			-- ----
+			-- Get the attribute definition
+			-- ----
+			SELECT * INTO v_attr
+			FROM pg_namespace N
+			JOIN pg_class C
+				ON N.oid = C.relnamespace
+			JOIN pg_attribute A
+				ON C.oid = A.attrelid
+			WHERE A.attrelid = v_attrdef.adrelid
+				AND A.attnum = v_attrdef.adnum;
+
+			IF NOT FOUND THEN
+				RAISE EXCEPTION 'Attribute for % not found', v_attrdef.adstr;
+			END IF;
+
+			-- ----
+			-- Get the sequence definition
+			-- ----
+			SELECT * INTO v_seq
+			FROM pg_namespace N
+			JOIN pg_class C
+				ON N.oid = C.relnamespace
+			WHERE C.oid = p_seqid;
+
+			IF NOT FOUND THEN
+				RAISE EXCEPTION 'Sequence with Oid % not found', p_seqid;
+			END IF;
+
+			-- ----
+			-- If the attribute type is not bigint, we change it
+			-- ----
+			v_num_altered = v_num_altered +
+				snowflake.convert_column_to_int8(v_attr.attrelid, v_attr.attnum);
+
+			-- ----
+			-- Now we can change the default to snowflake.nextval()
+			-- ----
+			v_cmd = 'ALTER TABLE ' ||
+				quote_ident(v_attr.nspname) || '.' ||
+				quote_ident(v_attr.relname) ||
+				' ALTER COLUMN ' ||
+				quote_ident(v_attr.attname) ||
+				' SET DEFAULT snowflake.nextval(' ||
+				quote_literal(
+					quote_ident(v_seq.nspname) || '.' ||
+					quote_ident(v_seq.relname)
+				) ||
+				'::regclass)';
+			RAISE NOTICE 'EXECUTE %', v_cmd;
+			EXECUTE v_cmd;
+
+			v_num_altered = v_num_altered + 1;
+		END LOOP;
+	END IF;
+
+	-- Note: for plain sequences not associated with columns, we still
+	-- fall through to here so snowflake can be used, to support
+	-- sequences used explicitly by applications
+
+	-- ----
+	-- Finally we need to change the sequence itself to settings that
+	-- prevent pg_catalog.nextval() from working. We do this by setting
+	-- the sequence's MAXVAL to its current last_value + 1, then invoke
+	-- our own nextval() function to bump it.
+	-- ----
+	v_cmd = 'SELECT last_value FROM ' ||
+		pg_catalog.quote_ident(N.nspname) || '.' ||
+		pg_catalog.quote_ident(C.relname)
+		FROM pg_catalog.pg_class C
+		JOIN pg_catalog.pg_namespace N ON N.oid = C.relnamespace
+		WHERE C.oid = p_seqid;
+	EXECUTE v_cmd INTO v_last_value;
+
+	v_cmd = 'ALTER SEQUENCE ' ||
+		pg_catalog.quote_ident(N.nspname) || '.' ||
+		pg_catalog.quote_ident(C.relname) ||
+		' NO CYCLE MAXVALUE ' ||
+		v_last_value + 1
+		FROM pg_catalog.pg_class C
+		JOIN pg_catalog.pg_namespace N ON N.oid = C.relnamespace
+		WHERE C.oid = p_seqid;
+	RAISE NOTICE '%', v_cmd;
+	EXECUTE v_cmd;
+
+	PERFORM snowflake.nextval(p_seqid);
+	RETURN v_num_altered;
+END;
+$$ LANGUAGE plpgsql;

snowflake.control

@@ -1,6 +1,6 @@
 # snowflake extension
 comment = 'Snowflake style IDs for PostgreSQL'
-default_version = '2.3'
+default_version = '2.4'
 module_pathname = '$libdir/snowflake'
 relocatable = false
 schema = snowflake

sql/conversion.sql

@@ -74,6 +74,15 @@ SELECT
 	z <= 42 AS is_not_snowflake_value
 FROM t3 ORDER BY x;
 
+-- Explict default
+CREATE SEQUENCE favorite_seq;
+CREATE TABLE t4 (x integer DEFAULT nextval('favorite_seq'::regclass));
+INSERT INTO t4 values (DEFAULT);
+SELECT * FROM t4;
+SELECT snowflake.convert_sequence_to_snowflake('favorite_seq');
+INSERT INTO t4 values (DEFAULT);
+SELECT x <= 42 AS is_not_snowflake_value FROM t4 ORDER BY x;
+
 -- Cleanup
-DROP TABLE t1,t2,t3 CASCADE;
+DROP TABLE t1,t2,t3,t4 CASCADE;
 DROP EXTENSION snowflake;