-- Bug fix: New feature for refresh snap that skips the data pull if nothing changed on the source wasn't properly setting the last_run value in the config table. Could cause the job monitor to think the refresh job had not been run.

/*
 *  Snap refresh to repull all table data
 */
CREATE OR REPLACE FUNCTION refresh_snap(p_destination text, p_index boolean DEFAULT true, p_debug boolean DEFAULT false, p_pulldata boolean DEFAULT true) RETURNS void
    LANGUAGE plpgsql SECURITY DEFINER
    AS $$
DECLARE

v_adv_lock          boolean; 
v_cols_n_types      text[];
v_cols              text[];
v_condition         text;
v_create_sql        text;
v_dblink            int;
v_dblink_name       text;
v_dblink_schema     text;
v_dest_table        text;
v_exists            int;
v_fetch_sql         text;
v_filter            text[];
v_insert_sql        text;
v_job_id            int;
v_jobmon_schema     text;
v_job_name          text;
v_lcols_array       text[];
v_local_sql         text;
v_l                 text;
v_match             boolean = true;
v_old_grant         record;
v_old_owner         text;
v_old_search_path   text;
v_old_snap          text;
v_old_snap_table    text;
v_parts             record;
v_post_script       text[];
v_refresh_snap      text;
v_remote_index_sql  text;
v_remote_sql        text;
v_row               record;
v_rowcount          bigint;
v_r                 text;
v_snap              text;
v_source_table      text;
v_step_id           int;
v_table_exists      int;
v_total             bigint := 0;
v_tup_del           bigint;
v_tup_ins           bigint;
v_tup_upd           bigint;
v_tup_del_new       bigint;
v_tup_ins_new       bigint;
v_tup_upd_new       bigint;
v_view_definition   text;

BEGIN

IF p_debug IS DISTINCT FROM true THEN
    PERFORM set_config( 'client_min_messages', 'notice', true );
END IF;

v_job_name := 'Refresh Snap: '||p_destination;
v_dblink_name := 'mimeo_snap_refresh_'||p_destination;

SELECT nspname INTO v_dblink_schema FROM pg_namespace n, pg_extension e WHERE e.extname = 'dblink' AND e.extnamespace = n.oid;
SELECT nspname INTO v_jobmon_schema FROM pg_namespace n, pg_extension e WHERE e.extname = 'pg_jobmon' AND e.extnamespace = n.oid;

-- Set custom search path to allow easier calls to other functions, especially job logging
SELECT current_setting('search_path') INTO v_old_search_path;
EXECUTE 'SELECT set_config(''search_path'',''@extschema@,'||v_jobmon_schema||','||v_dblink_schema||',public'',''false'')';

v_job_id := add_job(v_job_name);
PERFORM gdb(p_debug,'Job ID: '||v_job_id::text);

-- Take advisory lock to prevent multiple calls to function overlapping and causing possible deadlock
v_adv_lock := pg_try_advisory_lock(hashtext('refresh_snap'), hashtext(v_job_name));
IF v_adv_lock = 'false' THEN
    v_step_id := add_step(v_job_id,'Obtaining advisory lock for job: '||v_job_name);
    PERFORM gdb(p_debug,'Obtaining advisory lock FAILED for job: '||v_job_name);
    PERFORM update_step(v_step_id, 'WARNING','Found concurrent job. Exiting gracefully');
    PERFORM fail_job(v_job_id, 2);
    EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
    RETURN;
END IF;

v_step_id := add_step(v_job_id,'Grabbing Mapping, Building SQL');

SELECT source_table
    , dest_table
    , dblink
    , filter
    , condition
    , n_tup_ins
    , n_tup_upd
    , n_tup_del
    , post_script 
INTO v_source_table
    , v_dest_table
    , v_dblink
    , v_filter
    , v_condition
    , v_tup_ins
    , v_tup_upd
    , v_tup_del
    , v_post_script 
FROM refresh_config_snap
WHERE dest_table = p_destination; 
IF NOT FOUND THEN
   RAISE EXCEPTION 'ERROR: This table is not set up for snapshot replication: %',v_job_name; 
END IF;  

-- checking for current view

SELECT definition INTO v_view_definition FROM pg_views where
      ((schemaname || '.') || viewname)=v_dest_table;

PERFORM dblink_connect(v_dblink_name, @extschema@.auth(v_dblink));

v_remote_sql := 'SELECT array_agg(attname) as cols, array_agg(attname||'' ''||format_type(atttypid, atttypmod)::text) as cols_n_types FROM pg_attribute WHERE attrelid = '||quote_literal(v_source_table)||'::regclass AND attnum > 0 AND attisdropped is false';

-- Apply column filters if used
IF v_filter IS NOT NULL THEN
    v_remote_sql := v_remote_sql || ' AND ARRAY[attname::text] <@ '||quote_literal(v_filter);
END IF;

v_remote_sql := 'SELECT cols, cols_n_types FROM dblink('||quote_literal(v_dblink_name)||', ' || quote_literal(v_remote_sql) || ') t (cols text[], cols_n_types text[])';
PERFORM gdb(p_debug,'v_remote_sql: '||v_remote_sql);
EXECUTE v_remote_sql INTO v_cols, v_cols_n_types;  
PERFORM gdb(p_debug,'v_cols: {'|| array_to_string(v_cols, ',') ||'}');
PERFORM gdb(p_debug,'v_cols_n_types: {'|| array_to_string(v_cols_n_types, ',') ||'}');

PERFORM update_step(v_step_id, 'OK','Done');

v_step_id := add_step(v_job_id,'Truncate non-active snap table');

v_exists := strpos(v_view_definition, 'snap1');
  IF v_exists > 0 THEN
    v_snap := '_snap2';
    v_old_snap := '_snap1';
    ELSE
    v_snap := '_snap1';
    v_old_snap := '_snap2';
 END IF;
v_refresh_snap := v_dest_table||v_snap;
v_old_snap_table := v_dest_table||v_old_snap;
PERFORM gdb(p_debug,'v_refresh_snap: '||v_refresh_snap::text);

SELECT string_to_array(v_refresh_snap, '.') AS oparts INTO v_parts;

-- Create snap table if it doesn't exist
SELECT INTO v_table_exists count(1) FROM pg_tables WHERE schemaname ||'.'|| tablename = v_refresh_snap;
IF v_table_exists = 0 THEN
    PERFORM gdb(p_debug,'Snap table does not exist. Creating... ');    
    v_create_sql := 'CREATE TABLE ' || v_refresh_snap || ' (' || array_to_string(v_cols_n_types, ',') || ')';
    perform gdb(p_debug,'v_create_sql: '||v_create_sql::text);
    EXECUTE v_create_sql;
ELSE 
/* Check local column definitions against remote and recreate table if different. Allows automatic recreation of
        snap tables if columns change (add, drop type change)  */  
    v_local_sql := 'SELECT array_agg(attname||'' ''||format_type(atttypid, atttypmod)::text) as cols_n_types FROM pg_attribute WHERE attnum > 0 AND attisdropped is false AND attrelid = ' || quote_literal(v_refresh_snap) || '::regclass'; 
        
    PERFORM gdb(p_debug, v_local_sql);

    EXECUTE v_local_sql INTO v_lcols_array;
    -- Check to see if there's a change in the column structure on the remote
    FOREACH v_r IN ARRAY v_cols_n_types LOOP
        v_match := false;
        FOREACH v_l IN ARRAY v_lcols_array LOOP
            IF v_r = v_l THEN
                v_match := true;
                EXIT;
            END IF;
        END LOOP;
    END LOOP;

    IF v_match = false THEN
        -- Grab old table & view privileges. They are applied later after the view is recreated/swapped
        CREATE TEMP TABLE mimeo_snapshot_grants_tmp (statement text);
        FOR v_old_grant IN 
            SELECT table_schema ||'.'|| table_name AS tablename
                , array_agg(privilege_type::text) AS types
                , grantee
            FROM information_schema.table_privileges 
            WHERE table_schema ||'.'|| table_name IN (v_refresh_snap, v_dest_table)
            GROUP BY grantee, table_schema, table_name 
        LOOP
            INSERT INTO mimeo_snapshot_grants_tmp VALUES ( 
                'GRANT '||array_to_string(v_old_grant.types, ',')||' ON '||v_old_grant.tablename||' TO '||v_old_grant.grantee
            );
        END LOOP;
        SELECT viewowner INTO v_old_owner FROM pg_views WHERE schemaname ||'.'|| viewname = v_dest_table;

        EXECUTE 'DROP TABLE ' || v_refresh_snap;
        EXECUTE 'DROP VIEW ' || v_dest_table;
        v_create_sql := 'CREATE TABLE ' || v_refresh_snap || ' (' || array_to_string(v_cols_n_types, ',') || ')';
        PERFORM gdb(p_debug,'v_create_sql: '||v_create_sql::text);
        EXECUTE v_create_sql;
        v_step_id := add_step(v_job_id,'Source table structure changed.');
        PERFORM update_step(v_step_id, 'OK','Tables and view dropped and recreated. Please double-check snap table attributes (permissions, indexes, etc');
        PERFORM gdb(p_debug,'Source table structure changed. Tables and view dropped and recreated. Please double-check snap table attributes (permissions, indexes, etc)');
    END IF;
    -- truncate non-active snap table
    EXECUTE 'TRUNCATE TABLE ' || v_refresh_snap;

    PERFORM update_step(v_step_id, 'OK','Done');
END IF;

-- Only check the remote data if there have been no column changes and snap table actually exists. 
-- Otherwise maker functions won't work if source is empty & view switch won't happen properly.
IF  v_table_exists > 0 AND v_match THEN
    v_remote_sql := 'SELECT n_tup_ins, n_tup_upd, n_tup_del FROM pg_catalog.pg_stat_all_tables WHERE relid::regclass = '||quote_literal(v_source_table)||'::regclass';
    v_remote_sql := 'SELECT n_tup_ins, n_tup_upd, n_tup_del FROM dblink('||quote_literal(v_dblink_name)||', ' || quote_literal(v_remote_sql) || ') t (n_tup_ins bigint, n_tup_upd bigint, n_tup_del bigint)';
    perform gdb(p_debug,'v_remote_sql: '||v_remote_sql);
    EXECUTE v_remote_sql INTO v_tup_ins_new, v_tup_upd_new, v_tup_del_new;
    IF v_tup_ins_new = v_tup_ins AND v_tup_upd_new = v_tup_upd AND v_tup_del_new = v_tup_del THEN
        PERFORM gdb(p_debug,'Remote table has not had any writes. Skipping data pull');
        PERFORM update_step(v_step_id, 'OK', 'Remote table has not had any writes. Skipping data pull');
        UPDATE refresh_config_snap SET last_run = CURRENT_TIMESTAMP WHERE dest_table = p_destination;  
        PERFORM dblink_disconnect(v_dblink_name);
        PERFORM close_job(v_job_id);
        EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
        PERFORM pg_advisory_unlock(hashtext('refresh_snap'), hashtext(v_job_name));
        RETURN;
    END IF;
END IF;

v_remote_sql := 'SELECT '|| array_to_string(v_cols, ',') ||' FROM '||v_source_table;
-- Used by p_pull options in all maker functions to be able to create a replication job but pull no data
IF p_pulldata = false THEN
    v_remote_sql := v_remote_sql || ' LIMIT 0';
ELSIF v_condition IS NOT NULL THEN
    v_remote_sql := v_remote_sql || ' ' || v_condition;
END IF;

v_step_id := add_step(v_job_id,'Inserting records into local table');
PERFORM dblink_open(v_dblink_name, 'mimeo_cursor', v_remote_sql);

v_rowcount := 0;
LOOP
    v_fetch_sql := 'INSERT INTO '|| v_refresh_snap ||' ('|| array_to_string(v_cols, ',') ||') 
        SELECT '||array_to_string(v_cols, ',')||' FROM dblink_fetch('||quote_literal(v_dblink_name)||', ''mimeo_cursor'', 50000) AS ('||array_to_string(v_cols_n_types, ',')||')';
    EXECUTE v_fetch_sql;
    GET DIAGNOSTICS v_rowcount = ROW_COUNT;
    EXIT WHEN v_rowcount = 0;
    v_total := v_total + coalesce(v_rowcount, 0);
    PERFORM gdb(p_debug,'Fetching rows in batches: '||v_total||' done so far.');
    PERFORM update_step(v_step_id, 'PENDING', 'Fetching rows in batches: '||v_total||' done so far.');
END LOOP;
PERFORM dblink_close(v_dblink_name, 'mimeo_cursor');

PERFORM update_step(v_step_id, 'OK','Inserted '||v_total||' rows');

-- Create indexes if new table was created
IF  (v_table_exists = 0 OR v_match = 'f') AND p_index = true THEN
    v_remote_index_sql := 'SELECT 
        CASE
            WHEN i.indisprimary IS true THEN ''primary''
            WHEN i.indisunique IS true THEN ''unique''
            ELSE ''index''
        END AS key_type,
        ( SELECT array_agg( a.attname ORDER by x.r ) 
            FROM pg_attribute a 
            JOIN ( SELECT k, row_number() over () as r 
                    FROM unnest(i.indkey) k ) as x 
            ON a.attnum = x.k AND a.attrelid = i.indrelid ';
    IF v_filter IS NOT NULL THEN
        v_remote_index_sql := v_remote_index_sql || ' WHERE ARRAY[a.attname::text] <@ '||quote_literal(v_filter);
    END IF;
    v_remote_index_sql := v_remote_index_sql || ') AS indkey_names
        FROM pg_index i
        WHERE i.indrelid = '||quote_literal(v_source_table)||'::regclass';

    FOR v_row IN EXECUTE 'SELECT key_type, indkey_names FROM dblink('||quote_literal(v_dblink_name)||', '||quote_literal(v_remote_index_sql)||') t (key_type text, indkey_names text[])' LOOP
        IF v_row.indkey_names IS NOT NULL THEN   -- If column filter is used, indkey_name column may be null
            IF v_row.key_type = 'primary' THEN
                RAISE NOTICE 'Creating primary key...';
                EXECUTE 'ALTER TABLE '||v_refresh_snap||' ADD CONSTRAINT '||v_parts.oparts[2]||'_'||array_to_string(v_row.indkey_names, '_')||'_idx PRIMARY KEY ('||array_to_string(v_row.indkey_names, ',')||')';
            ELSIF v_row.key_type = 'unique' THEN
                RAISE NOTICE 'Creating unique index...';
                EXECUTE 'CREATE UNIQUE INDEX '||v_parts.oparts[2]||'_'||array_to_string(v_row.indkey_names, '_')||'_idx ON '||v_refresh_snap|| '('||array_to_string(v_row.indkey_names, ',')||')';
            ELSE
                RAISE NOTICE 'Creating index...';
                EXECUTE 'CREATE INDEX '||v_parts.oparts[2]||'_'||array_to_string(v_row.indkey_names, '_')||'_idx ON '||v_refresh_snap|| '('||array_to_string(v_row.indkey_names, ',')||')';
            END IF;
        END IF;
    END LOOP;
END IF;

EXECUTE 'ANALYZE ' ||v_refresh_snap;

--SET statement_timeout='30 min';  

-- swap view
v_step_id := add_step(v_job_id,'Swap view to '||v_refresh_snap);
PERFORM gdb(p_debug,'Swapping view to '||v_refresh_snap);
EXECUTE 'CREATE OR REPLACE VIEW '||v_dest_table||' AS SELECT * FROM '||v_refresh_snap;
PERFORM update_step(v_step_id, 'OK','View Swapped');

IF v_match = false THEN
    -- Actually apply the original privileges if the table was recreated
    FOR v_old_grant IN SELECT statement FROM mimeo_snapshot_grants_tmp
    LOOP
        EXECUTE v_old_grant.statement;
    END LOOP;
    DROP TABLE IF EXISTS mimeo_snapshot_grants_tmp;
    EXECUTE 'ALTER VIEW '||v_dest_table||' OWNER TO '||v_old_owner;
    EXECUTE 'ALTER TABLE '||v_refresh_snap||' OWNER TO '||v_old_owner;

    -- Run any special sql to fix anything that was done to destination tables (extra indexes, etc)
    IF v_post_script IS NOT NULL THEN
        v_step_id := add_step(v_job_id,'Applying post_script sql commands due to schema change');
        PERFORM @extschema@.post_script(v_dest_table);
        PERFORM update_step(v_step_id, 'OK','Done');
    END IF;
END IF;

SELECT INTO v_table_exists count(1) FROM pg_tables WHERE schemaname ||'.'|| tablename = v_old_snap_table;
IF v_table_exists > 0 THEN
    v_step_id := add_step(v_job_id,'Truncating old snap table');
    EXECUTE 'TRUNCATE TABLE '||v_old_snap_table;
    PERFORM update_step(v_step_id, 'OK','Done');
END IF;

v_step_id := add_step(v_job_id,'Updating last_run & tuple change values');
UPDATE refresh_config_snap SET 
    last_run = CURRENT_TIMESTAMP 
    , n_tup_ins = v_tup_ins_new   
    , n_tup_upd = v_tup_upd_new
    , n_tup_del = v_tup_del_new
WHERE dest_table = p_destination;  
PERFORM update_step(v_step_id, 'OK','Done');

PERFORM dblink_disconnect(v_dblink_name);

PERFORM close_job(v_job_id);

-- Ensure old search path is reset for the current session
EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';

PERFORM pg_advisory_unlock(hashtext('refresh_snap'), hashtext(v_job_name));

EXCEPTION
    WHEN QUERY_CANCELED THEN
        EXECUTE 'SELECT set_config(''search_path'',''@extschema@,'||v_jobmon_schema||','||v_dblink_schema||''',''false'')';
        IF dblink_get_connections() @> ARRAY[v_dblink_name] THEN
            PERFORM dblink_disconnect(v_dblink_name);
        END IF;
        EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
        PERFORM pg_advisory_unlock(hashtext('refresh_snap'), hashtext(v_job_name));
        RAISE EXCEPTION '%', SQLERRM;   
    WHEN OTHERS THEN
        EXECUTE 'SELECT set_config(''search_path'',''@extschema@,'||v_jobmon_schema||','||v_dblink_schema||''',''false'')';
        IF v_job_id IS NULL THEN
            v_job_id := add_job('Refresh Snap: '||p_destination);
            v_step_id := add_step(v_job_id, 'EXCEPTION before job logging started');
        END IF;
        IF v_step_id IS NULL THEN
            v_step_id := add_step(v_job_id, 'EXCEPTION before first step logged');
        END IF;
        PERFORM update_step(v_step_id, 'CRITICAL', 'ERROR: '||coalesce(SQLERRM,'unknown'));
        PERFORM fail_job(v_job_id);
        IF dblink_get_connections() @> ARRAY[v_dblink_name] THEN
            PERFORM dblink_disconnect(v_dblink_name);
        END IF;
        EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
        PERFORM pg_advisory_unlock(hashtext('refresh_snap'), hashtext(v_job_name));
        RAISE EXCEPTION '%', SQLERRM;
END
$$;