pgrw_xyroute is an example of a wrapper around the pgr_trsp function to require only x/y inputs for source and target points. Routing is then done by pgr_trsp using the nearest location on the closest edges to the source and target points.

pgrw_xyroute.sql

/*
 pgrw_xyroute is an example of a wrapper around the pgr_trsp function to require only x/y inputs
 for source and target points. Routing is then done by pgr_trsp using the nearest location on 
 the closest edges to the source and target points. To achieve this result, the details of the 
 specific routing network are hard-coded as constants in the wrapper. Modification to your 
 specific situation should be simple.
*/

CREATE OR REPLACE FUNCTION pgrw_xyroute(source_x double precision, source_y double precision, 
                                        target_x double precision, target_y double precision)
RETURNS SETOF pgr_costresult
AS
$BODY$
DECLARE
    edge_tbl_name CONSTANT TEXT = '_rt_geom_streets_base';   -- edge table name
    srid          CONSTANT INTEGER = 2264;                   -- edge table and x,y srid
    cost_column   CONSTANT TEXT = 'cost_len';                -- cost_len   |  cost_time
    rcost_column  CONSTANT TEXT = 'rcost_len';               -- rcost_len  |  rcost_time
    local_radius  CONSTANT DOUBLE PRECISION = 5280.0;        -- radius in ft. for selecting all edges around point

    -- sql to locate the closest edge to the source and target points is built from sql1, sql2, sql3 & sql4
    --     SELECT 
    --         id, 
    --         ST_LineLocatePoint(the_geom, ST_SetSRID(ST_Point( source_x, source_x), srid)) AS fraction 
    --     FROM edge_tbl_name
    --     WHERE ST_DWithin(the_geom, ST_SetSRID(ST_Point(source_x, source_x), srid), local_radius)
    --     ORDER BY ST_Distance(the_geom, ST_SetSRID(ST_Point(source_x, source_y), srid)) ASC
    --     LIMIT 1
    -- returns a record (id, fraction)
    sql1 CONSTANT TEXT =  'SELECT id, ST_LineLocatePoint(the_geom, ';
                           --   point definition sql goes here
    sql2 CONSTANT TEXT =  ') AS fraction FROM ' || edge_tbl_name || ' WHERE ST_DWithin(the_geom, ';
                           --   point definition sql goes here
    sql3 CONSTANT TEXT =  ', ' || local_radius || ') ORDER BY ST_Distance(the_geom, ';    
                           --   point definition sql goes here
    sql4 CONSTANT TEXT =  ') ASC LIMIT 1';

    -- this defines the select for ALL edges in the edge table
    edge_select CONSTANT TEXT =  'SELECT
           id, source, target, ' || cost_column || ' AS cost, ' || cost_column || ' AS reverse_cost
	FROM '  || edge_tbl_name;

    -- WHERE clause to limit edges to major roads
    major_roads_where CONSTANT TEXT = $$ WHERE sd_flag = 'ROADS' $$;

    source_point  TEXT;     -- point definition sql for source point
    target_point  TEXT;     -- point definition sql for target point
    source_edge   RECORD;   -- nearest edge to source point
    target_edge   RECORD;   -- nearest edge to target point
    edge_sql      TEXT;     -- sql to select edges to use for routing
    
BEGIN
    -- point definition sql for source point
    source_point = 'ST_SetSRID(ST_Point(' || source_x || ',' || source_y || '), ' || srid || ')';
    EXECUTE sql1 || source_point || sql2 || source_point || sql3  || source_point || sql4 
    INTO source_edge;

    IF source_edge.id IS NULL THEN
        RAISE NOTICE '** source_edge.id IS NULL **';
    END IF;

    -- point definition sql for target point
    target_point = 'ST_SetSRID(ST_Point(' || target_x || ',' || target_y || '), ' || srid || ')';
    EXECUTE sql1 || target_point || sql2 || target_point || sql3 || target_point || sql4 
    INTO target_edge;

    IF target_edge.id IS NULL THEN
        RAISE NOTICE '** target_edge.id IS NULL **';
    END IF;

    -- there are three edge selects unioned here:
    --    all edges within 'local_radius' of the source point
    --    all 'Major' roads in the table (marked with sd_flag='ROADS')
    --    all edges within 'street_radius' of the target point
    edge_sql :=   edge_select || ' WHERE ST_DWithin(the_geom, ' || source_point || ', ' || local_radius || ')
	    UNION '|| edge_select || major_roads_where || '
	    UNION '|| edge_select || ' WHERE ST_DWithin(the_geom, ' || target_point || ', ' || local_radius || ')
    ';

    RETURN QUERY SELECT *
        FROM pgr_trsp(edge_sql, source_edge.id, source_edge.fraction, target_edge.id, target_edge.fraction, TRUE, TRUE);
END;
$BODY$
  LANGUAGE plpgsql IMMUTABLE
  COST 100
  ROWS 1000;

/*

-- test function only
SELECT (pgrw_xyroute(2088111,731419,2088111,700700)).*;

-- get all edge data for route
WITH route AS (
  SELECT (pgrw_xyroute(2088111,731419,2088111,700700)).*
) 
SELECT *
FROM _rt_geom_streets_base edges
JOIN route
  ON edges.id = route.id2

*/