Error sequence has no max_value when copying database schema - postgresql

Question

I'm trying to copy database schema using a function from Copy schema and create new schema with different name in the same data base
-- Function: clone_schema(text, text)
-- DROP FUNCTION clone_schema(text, text);
CREATE OR REPLACE FUNCTION clone_schema(
source_schema text,
dest_schema text,
include_recs boolean)
RETURNS void AS
$BODY$
-- This function will clone all sequences, tables, data, views & functions from any existing schema to a new one
-- SAMPLE CALL:
-- SELECT clone_schema('public', 'new_schema', TRUE);
DECLARE
src_oid oid;
tbl_oid oid;
func_oid oid;
table_rec record;
seq_rec record;
object text;
sequence_ text;
table_ text;
buffer text;
seq_buffer text;
table_buffer text;
srctbl text;
default_ text;
column_ text;
qry text;
dest_qry text;
v_def text;
seqval bigint;
sq_last_value bigint;
sq_max_value bigint;
sq_start_value bigint;
sq_increment_by bigint;
sq_min_value bigint;
sq_cache_value bigint;
sq_log_cnt bigint;
sq_is_called boolean;
sq_is_cycled boolean;
sq_cycled char(10);
BEGIN
-- Check that source_schema exists
SELECT oid INTO src_oid
FROM pg_namespace
WHERE nspname = source_schema;
IF NOT FOUND
THEN
RAISE EXCEPTION 'source schema % does not exist!', source_schema;
RETURN ;
END IF;
-- Check that dest_schema does not yet exist
PERFORM nspname
FROM pg_namespace
WHERE nspname = dest_schema;
IF FOUND
THEN
RAISE EXCEPTION 'dest schema % already exists!', dest_schema;
RETURN ;
END IF;
EXECUTE 'CREATE SCHEMA "' || dest_schema || '"';
-- Create tables
FOR object IN
SELECT TABLE_NAME::text
FROM information_schema.tables
WHERE table_schema = source_schema
AND table_type = 'BASE TABLE'
LOOP
buffer := '"' || dest_schema || '".' || quote_ident(object);
EXECUTE 'CREATE TABLE ' || buffer || ' (LIKE "' || source_schema || '".' || quote_ident(object)
|| ' INCLUDING ALL);';
IF include_recs
THEN
-- Insert records from source table
EXECUTE 'INSERT INTO ' || buffer || ' SELECT * FROM "' || source_schema || '".' || quote_ident(object) || ';';
END IF;
END LOOP;
-- add FK constraint
FOR qry IN
SELECT 'ALTER TABLE "' || dest_schema || '".' || quote_ident(rn.relname)
|| ' ADD CONSTRAINT ' || quote_ident(ct.conname) || ' ' || pg_get_constraintdef(ct.oid) || ';'
FROM pg_constraint ct
JOIN pg_class rn ON rn.oid = ct.conrelid
WHERE connamespace = src_oid
AND rn.relkind = 'r'
AND ct.contype = 'f'
LOOP
EXECUTE qry;
END LOOP;
-- Create sequences
FOR seq_rec IN
SELECT
s.sequence_name::text,
table_name,
column_name
FROM information_schema.sequences s
JOIN (
SELECT
substring(column_default from E'^nextval\\(''(?:[^"'']?.*["'']?\\.)?([^'']*)''(?:::text|::regclass)?\\)')::text as seq_name,
table_name,
column_name
FROM information_schema.columns
WHERE column_default LIKE 'nextval%'
AND table_schema = source_schema
) c ON c.seq_name = s.sequence_name
WHERE sequence_schema = source_schema
LOOP
seq_buffer := quote_ident(dest_schema) || '.' || quote_ident(seq_rec.sequence_name);
EXECUTE 'CREATE SEQUENCE ' || seq_buffer || ';';
qry := 'SELECT last_value, max_value, start_value, increment_by, min_value, cache_value, log_cnt, is_cycled, is_called
FROM "' || source_schema || '".' || quote_ident(seq_rec.sequence_name) || ';';
EXECUTE qry INTO sq_last_value, sq_max_value, sq_start_value, sq_increment_by, sq_min_value, sq_cache_value, sq_log_cnt, sq_is_cycled, sq_is_called ;
IF sq_is_cycled
THEN
sq_cycled := 'CYCLE';
ELSE
sq_cycled := 'NO CYCLE';
END IF;
EXECUTE 'ALTER SEQUENCE ' || seq_buffer
|| ' INCREMENT BY ' || sq_increment_by
|| ' MINVALUE ' || sq_min_value
|| ' MAXVALUE ' || sq_max_value
|| ' START WITH ' || sq_start_value
|| ' RESTART ' || sq_min_value
|| ' CACHE ' || sq_cache_value
|| ' OWNED BY ' || quote_ident(dest_schema ) || '.'
|| quote_ident(seq_rec.table_name) || '.'
|| quote_ident(seq_rec.column_name) || ' '
|| sq_cycled || ' ;' ;
IF include_recs
THEN
EXECUTE 'SELECT setval( ''' || seq_buffer || ''', ' || sq_last_value || ', ' || sq_is_called || ');' ;
ELSE
EXECUTE 'SELECT setval( ''' || seq_buffer || ''', ' || sq_start_value || ', ' || sq_is_called || ');' ;
END IF;
table_buffer := quote_ident(dest_schema) || '.' || quote_ident(seq_rec.table_name);
FOR table_rec IN
SELECT column_name::text AS column_,
REPLACE(column_default::text, source_schema, quote_ident(dest_schema)) AS default_
FROM information_schema.COLUMNS
WHERE table_schema = dest_schema
AND TABLE_NAME = seq_rec.table_name
AND column_default LIKE 'nextval(%' || seq_rec.sequence_name || '%::regclass)'
LOOP
EXECUTE 'ALTER TABLE ' || table_buffer || ' ALTER COLUMN ' || table_rec.column_ || ' SET DEFAULT nextval(' || quote_literal(seq_buffer) || '::regclass);';
END LOOP;
END LOOP;
-- Create views
FOR object IN
SELECT table_name::text,
view_definition
FROM information_schema.views
WHERE table_schema = source_schema
LOOP
buffer := '"' || dest_schema || '".' || quote_ident(object);
SELECT view_definition INTO v_def
FROM information_schema.views
WHERE table_schema = source_schema
AND table_name = quote_ident(object);
EXECUTE 'CREATE OR REPLACE VIEW ' || buffer || ' AS ' || v_def || ';' ;
END LOOP;
-- Create functions
FOR func_oid IN
SELECT oid
FROM pg_proc
WHERE pronamespace = src_oid
LOOP
SELECT pg_get_functiondef(func_oid) INTO qry;
SELECT replace(qry, source_schema, dest_schema) INTO dest_qry;
EXECUTE dest_qry;
END LOOP;
RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
But when I'm trying to execute this I'm getting an error:
ERROR: column "max_value" does not exist
Perhaps you meant to reference the column "dict_test_value_seq.last_value"
When I'm trying to get max_value of that sequence I get it properly. How can be this function improved to get sequences values?

Answer 1

You are using a version of PostgreSQL that is 10 or greater, meaning that you can no longer get the max_value by selecting from the sequence. Instead, you need to access the pg_sequence catalog, but you may want to simplify queries by just using the information_schema.sequences view:
SELECT start_value, minimum_value, maximum_value, increment, cycle_option
FROM information_schema.sequences
WHERE (sequence_schema, sequence_name) = ('schemaname','mysequence');