1.23. altertableforreplication( integer )

Function Properties

Language: PLPGSQL

Return Type: integer

alterTableForReplication(tab_id) Sets up a table for replication. On the origin, this involves adding the "logTrigger()" trigger to the table. On a subscriber node, this involves disabling triggers and rules, and adding in the trigger that denies write access to replicated tables.

declare
	p_tab_id			alias for $1;
	v_no_id				int4;
	v_tab_row			record;
	v_tab_fqname		text;
	v_tab_attkind		text;
	v_n					int4;
	v_trec	record;
	v_tgbad	boolean;
begin
	-- ----
	-- Grab the central configuration lock
	-- ----
	lock table sl_config_lock;

	-- ----
	-- Get our local node ID
	-- ----
	v_no_id := getLocalNodeId('_schemadoc');

	-- ----
	-- Get the sl_table row and the current origin of the table. 
	-- Verify that the table currently is NOT in altered state.
	-- ----
	select T.tab_reloid, T.tab_set, T.tab_idxname, T.tab_altered,
			S.set_origin, PGX.indexrelid,
			slon_quote_brute(PGN.nspname) || '.' ||
			slon_quote_brute(PGC.relname) as tab_fqname
			into v_tab_row
			from sl_table T, sl_set S,
				"pg_catalog".pg_class PGC, "pg_catalog".pg_namespace PGN,
				"pg_catalog".pg_index PGX, "pg_catalog".pg_class PGXC
			where T.tab_id = p_tab_id
				and T.tab_set = S.set_id
				and T.tab_reloid = PGC.oid
				and PGC.relnamespace = PGN.oid
				and PGX.indrelid = T.tab_reloid
				and PGX.indexrelid = PGXC.oid
				and PGXC.relname = T.tab_idxname
				for update;
	if not found then
		raise exception 'Slony-I: alterTableForReplication(): Table with id % not found', p_tab_id;
	end if;
	v_tab_fqname = v_tab_row.tab_fqname;
	if v_tab_row.tab_altered then
		raise exception 'Slony-I: alterTableForReplication(): Table % is already in altered state',
				v_tab_fqname;
	end if;

	v_tab_attkind := determineAttKindUnique(v_tab_row.tab_fqname, 
						v_tab_row.tab_idxname);

	execute 'lock table ' || v_tab_fqname || ' in access exclusive mode';

	-- ----
	-- Procedures are different on origin and subscriber
	-- ----
	if v_no_id = v_tab_row.set_origin then
		-- ----
		-- On the Origin we add the log trigger to the table and done
		-- ----
		execute 'create trigger "_schemadoc_logtrigger_' || 
				p_tab_id || '" after insert or update or delete on ' ||
				v_tab_fqname || ' for each row execute procedure
				logTrigger (''_schemadoc'', ''' || 
					p_tab_id || ''', ''' || 
					v_tab_attkind || ''');';
	else
		-- ----
		-- On the subscriber the thing is a bit more difficult. We want
		-- to disable all user- and foreign key triggers and rules.
		-- ----


		-- ----
		-- Check to see if there are any trigger conflicts...
		-- ----
		v_tgbad := 'false';
		for v_trec in 
			select pc.relname, tg1.tgname from
			"pg_catalog".pg_trigger tg1, 
			"pg_catalog".pg_trigger tg2,
			"pg_catalog".pg_class pc,
			"pg_catalog".pg_index pi,
			sl_table tab
			where 
			 tg1.tgname = tg2.tgname and        -- Trigger names match
			 tg1.tgrelid = tab.tab_reloid and   -- trigger 1 is on the table
			 pi.indexrelid = tg2.tgrelid and    -- trigger 2 is on the index
			 pi.indrelid = tab.tab_reloid and   -- indexes table is this table
			 pc.oid = tab.tab_reloid
                loop
			raise notice 'Slony-I: alterTableForReplication(): multiple instances of trigger % on table %',
				v_trec.tgname, v_trec.relname;
			v_tgbad := 'true';
		end loop;
		if v_tgbad then
			raise exception 'Slony-I: Unable to disable triggers';
		end if;  		

		-- ----
		-- Disable all existing triggers
		-- ----
		update "pg_catalog".pg_trigger
				set tgrelid = v_tab_row.indexrelid
				where tgrelid = v_tab_row.tab_reloid
				and not exists (
						select true from sl_table TAB,
								sl_trigger TRIG
								where TAB.tab_reloid = tgrelid
								and TAB.tab_id = TRIG.trig_tabid
								and TRIG.trig_tgname = tgname
					);
		get diagnostics v_n = row_count;
		if v_n > 0 then
			update "pg_catalog".pg_class
					set reltriggers = reltriggers - v_n
					where oid = v_tab_row.tab_reloid;
		end if;

		-- ----
		-- Disable all existing rules
		-- ----
		update "pg_catalog".pg_rewrite
				set ev_class = v_tab_row.indexrelid
				where ev_class = v_tab_row.tab_reloid;
		get diagnostics v_n = row_count;
		if v_n > 0 then
			update "pg_catalog".pg_class
					set relhasrules = false
					where oid = v_tab_row.tab_reloid;
		end if;

		-- ----
		-- Add the trigger that denies write access to replicated tables
		-- ----
		execute 'create trigger "_schemadoc_denyaccess_' || 
				p_tab_id || '" before insert or update or delete on ' ||
				v_tab_fqname || ' for each row execute procedure
				denyAccess (''_schemadoc'');';
	end if;

	-- ----
	-- Mark the table altered in our configuration
	-- ----
	update sl_table
			set tab_altered = true where tab_id = p_tab_id;

	return p_tab_id;
end;