DROP FUNCTION IF EXISTS public.generate_partitioning_of_an_existing_table_by_date_unix_time(text, text, integer, integer, text, boolean);

CREATE OR REPLACE FUNCTION public.generate_partitioning_of_an_existing_table_by_date_unix_time(
	tablename text,
	columnname text,
	start_year integer,
	end_year integer,
	step text,
	droptable boolean DEFAULT false)
    RETURNS void
    LANGUAGE 'plpgsql'
    
    VOLATILE PARALLEL UNSAFE
AS $BODY$
declare 	old_tablename      	TEXT;
		new_tablename      	 	TEXT;
		partition_tablename  	TEXT;
		start_interval    	 	TEXT;
	    end_interval        	TEXT;
		interations			 	INTEGER;		
		i					 	INTEGER;
		sql_str				 	TEXT = '';
		receive_constraints  	TEXT;
		receive_triggers	  	TEXT;
		toBeDeleted_constraints TEXT;
		lastvalue				INTEGER;
		exists_sequence			TEXT;
		tmp_sql					VARCHAR;
		renamed_indexes			TEXT;
		renamed_constraints		TEXT;
		toBeCreated_indexes     TEXT;
		start_unix_time    	 	TEXT;
	    end_unix_time        	TEXT;
		primary_key           	TEXT;
		sequence_id           	TEXT;
		
BEGIN

	IF start_year > end_year THEN
		RAISE NOTICE '%', 'start_year > end_year';
		RETURN;
	END IF;

	primary_key := '"posID"';
	sequence_id := '_posID_seq';
	
	new_tablename :=  'new_' || tablename;
	sql_str := format('-- create a new table having the same structure with specified table ' ||  CHR(13) ||
					  'CREATE TABLE ' || new_tablename || '(LIKE ' || tablename || ' INCLUDING DEFAULTS INCLUDING CONSTRAINTS) PARTITION BY RANGE(' || columnname || ');' || CHR(13) || CHR(13) ||
			 		  '-- create partiton for all other records that dont match with the partition condition'  ||  CHR(13) ||
					  'CREATE TABLE ' || tablename || '_default PARTITION OF ' || new_tablename || ' DEFAULT; ') ||  CHR(13);
	
	
	sql_str := sql_str || CHR(13) || get_query_partitioning_of_an_existing_table_by_date_unix_time(tablename , new_tablename, start_year, end_year, step);	
	
	sql_str := sql_str || CHR(13) || 
				 	'-- copy data into the new table ' || CHR(13) || 
					'INSERT INTO ' || new_tablename || '(SELECT * FROM ' || tablename || '); ' || CHR(13) ;
				

	RAISE NOTICE '%', sql_str;

    -- execute the query
    EXECUTE  sql_str;

	--===========================================================
	--  build the commands to rename the indexes
	--===========================================================	

	old_tablename := tablename;	

	SELECT string_agg( 'ALTER INDEX IF EXISTS "' || indexname || '" RENAME TO "old_' || indexname || '";' , CHR(13)) INTO renamed_indexes	
	FROM  pg_indexes pg
	WHERE pg.tablename = old_tablename
	AND   indexname NOT LIKE '%pkey%';

	SELECT string_agg( CASE WHEN contype = 'p' THEN -- primary key
					  	'ALTER INDEX IF EXISTS "' || conname || '" RENAME TO "old_' || conname || '";'
					   ELSE 
					  	'ALTER TABLE ' || old_tablename || ' RENAME CONSTRAINT "' || conname || '" TO "old_' || conname || '";' 
					   END 
					  , CHR(13)) INTO renamed_constraints	
						
	FROM pg_catalog.pg_constraint con
            INNER JOIN pg_catalog.pg_class rel ON rel.oid = con.conrelid
    WHERE rel.relname = old_tablename;

	--======================================================================
	--  build the commands to recreate the indexes on the partitioned table
	--======================================================================	

	SELECT string_agg( indexdef || ';' , CHR(13)) INTO toBeCreated_indexes
	FROM  pg_indexes pg
	WHERE pg.tablename = old_tablename
	AND   indexname NOT LIKE '%pkey%'
	AND   indexname NOT LIKE '%' || primary_key || '%'
	AND   indexdef  NOT LIKE '%UNIQUE%';
	
	

	--===========================================================
	-- save the foreign key into receive_constraints variable
	--===========================================================
	SELECT  string_agg(command  , CHR(13) )  INTO receive_constraints
	FROM ( 	SELECT   format('ALTER TABLE IF EXISTS "%s" ADD CONSTRAINT "%s" FOREIGN KEY ("%s") REFERENCES "%s"("%s");',
							 tablename,		 
							 tc.constraint_name, 
							 string_agg(distinct kcu.column_name, ','),
							 ccu.table_name, 
							 string_agg(distinct ccu.column_name, ',')) command
			FROM     information_schema.table_constraints AS tc 
			JOIN     information_schema.key_column_usage AS kcu
			ON       tc.constraint_name = kcu.constraint_name
			JOIN     information_schema.constraint_column_usage AS ccu
			ON       ccu.constraint_name = tc.constraint_name
			WHERE    constraint_type = 'FOREIGN KEY' 
			AND      tc.table_name = tablename
			GROUP BY tc.constraint_name, tc.table_name, ccu.table_name
	)x;
	
	--===========================================================
	-- save the triggers into receive_triggers variable
	--===========================================================
	SELECT  string_agg(command  , CHR(13) )  INTO receive_triggers
	FROM ( SELECT format( 'CREATE TRIGGER %s %s %s ON "%s" FOR EACH ROW %s ;', 
			   t1.trigger_name
			  ,t1.action_timing
			  ,t2.event_manipulation
			  ,t1.event_object_table
			  ,t1.action_statement ) as command
			  
			FROM ( 		SELECT DISTINCT 		   
							   trigger_name
							  ,action_timing
							  ,event_object_table
							  ,action_statement 
						FROM  information_schema.triggers
						WHERE event_object_table = tablename
				  ) t1 
				  INNER JOIN (SELECT trigger_name, string_agg(event_manipulation, ' OR ')  as event_manipulation
							  FROM information_schema.triggers
							   WHERE event_object_table =  tablename
							  GROUP BY trigger_name			
							  ) t2 	ON t1.trigger_name = t2.trigger_name
	)x;	  
	
		
	--===================================================================================================================
	-- save the constraints which refereces the specified tablename into toBeDeleted_constraints variable
	--===================================================================================================================
	SELECT string_agg( 'ALTER TABLE IF EXISTS "' || foreign_table || '" DROP CONSTRAINT IF EXISTS "' || constraint_name || '";' , CHR(13) ) INTO toBeDeleted_constraints 
 	FROM (
			 select kcu.table_name as foreign_table,
				   '>-' as rel,
				   rel_tco.table_schema || '.' || rel_tco.table_name as primary_table,
				   string_agg(kcu.column_name, ', ') as fk_columns,
				   kcu.constraint_name
			from information_schema.table_constraints tco
			join information_schema.key_column_usage kcu
					  on tco.constraint_schema = kcu.constraint_schema
					  and tco.constraint_name = kcu.constraint_name
			join information_schema.referential_constraints rco
					  on tco.constraint_schema = rco.constraint_schema
					  and tco.constraint_name = rco.constraint_name
			join information_schema.table_constraints rel_tco
					  on rco.unique_constraint_schema = rel_tco.constraint_schema
					  and rco.unique_constraint_name = rel_tco.constraint_name
			where tco.constraint_type = 'FOREIGN KEY'
			and   rel_tco.table_name  = tablename
			group by kcu.table_schema,
					 kcu.table_name,
					 rel_tco.table_name,
					 rel_tco.table_schema,
					 kcu.constraint_name
	)x;
	
	tmp_sql = ' SELECT ''exists'' FROM pg_class WHERE relname = ''' || tablename || sequence_id || ''';';
	EXECUTE tmp_sql INTO exists_sequence;
	
 	--RAISE NOTICE '%', COALESCE( exists_sequence, 'not exists');
	IF exists_sequence = 'exists' THEN
			EXECUTE format(' SELECT  last_value FROM "%s";',  tablename || sequence_id) INTO lastvalue;
	END IF;		   
				   
	  	    
	
    IF ( dropTable ) THEN 
	
		sql_str :=  '--====== dropTable = true ======-- ' || CHR(13) || CHR(13) ||
					'--    drop old table with cascade '	 || CHR(13) ||			
					'DROP TABLE IF EXISTS ' || tablename || ' CASCADE; ' || CHR(13) ||

					'-- rename the new table to old table ' 	|| CHR(13) ||		 
					'ALTER TABLE IF EXISTS ' || new_tablename || ' RENAME TO ' || tablename || ';'   || CHR(13) ||

					'-- create primary key ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || tablename || ' ADD CONSTRAINT ' || tablename || '_pkey PRIMARY KEY (' || primary_key || ',' || columnname || ');' || CHR(13) ||

					'-- create sequence ' || CHR(13) ||
					'CREATE SEQUENCE IF NOT EXISTS "' || tablename || sequence_id || '" INCREMENT 1 START ' || COALESCE(lastvalue,0) + 1 || ';'   || CHR(13) ||

					'-- set id to be taken from sequence ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || tablename || ' ALTER COLUMN ' || primary_key || ' SET DEFAULT nextval(''"' || tablename || sequence_id || '"'');' || CHR(13);
				
				
	ELSE 
		
			 sql_str :=  COALESCE( renamed_constraints, '')  || CHR(13) || 
			 			 COALESCE( renamed_indexes, '')      || CHR(13);		
			 EXECUTE  sql_str;
		
			sql_str :=  '--====== dropTable = false ( rename table )======-- ' || CHR(13) || CHR(13) ||
		
					'-- rename the current table to *_old ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || tablename     || ' RENAME TO ' || tablename || '_old; '  || CHR(13) ||

					'-- rename the new table ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || new_tablename || ' RENAME TO ' || tablename || ';'   || CHR(13) ||
 
					'-- create primary key ' || CHR(13) ||
		  			'ALTER TABLE IF EXISTS ' || tablename || ' ADD CONSTRAINT ' || tablename || '_pkey PRIMARY KEY (' || primary_key || ',' || columnname || ');' || CHR(13) ||

					'-- rename existing sequence as old ' || CHR(13) ||
					'ALTER SEQUENCE IF EXISTS "' || tablename || sequence_id || '" RENAME TO "' || tablename || '_old'  || sequence_id || '";' || CHR(13) ||

					'-- create sequence ' || CHR(13) ||
					'CREATE SEQUENCE IF NOT EXISTS "' || tablename || sequence_id || '" INCREMENT 1 START ' ||  COALESCE(lastvalue,0) + 1 || ';'   || CHR(13) ||

					'-- set id to be taken from sequence ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || tablename || '_old' || ' ALTER COLUMN ' || primary_key || ' SET DEFAULT nextval(''"' || tablename || '_old' || sequence_id || '"'');' || CHR(13) ||

					'-- set id to be taken from sequence ' || CHR(13) ||
					'ALTER TABLE IF EXISTS ' || tablename || ' ALTER COLUMN ' || primary_key || ' SET DEFAULT nextval(''"' || tablename || sequence_id || '"'');' || CHR(13);
					
	END IF; 

	sql_str := sql_str || COALESCE(toBeDeleted_constraints, '') || CHR(13) || COALESCE(receive_constraints, '') || CHR(13) || CHR(13) || COALESCE(receive_triggers, '');
	
	
	RAISE NOTICE '%', sql_str;

    -- execute the query
    EXECUTE  sql_str;
	
	
	sql_str := COALESCE(toBeCreated_indexes, '');
		
	RAISE NOTICE '%', sql_str;	
	EXECUTE  sql_str;

END;
$BODY$;