## 1.18. 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;
    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: 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: 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.
    		-- ----

    		-- ----
    		-- 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;