ST_Union.java

package com.esri.hadoop.hive;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.io.BytesWritable;


import com.esri.core.geometry.Geometry;
import com.esri.core.geometry.GeometryEngine;
import com.esri.core.geometry.SpatialReference;
import com.esri.hadoop.hive.GeometryUtils.OGCType;
import com.esri.core.geometry.ogc.OGCGeometry;

@Description(
		name = "ST_Union",
		value = "_FUNC_(ST_Geometry, ST_Geometry, ...) - returns an ST_Geometry as the union of the supplied ST_Geometries",
		extended = "Example: SELECT ST_AsText(ST_Union(ST_Polygon(1, 1, 1, 4, 4, 4, 4, 1), ST_Polygon(4, 1, 4, 4, 4, 8, 8, 1))) FROM onerow;\n" + 
		"MULTIPOLYGON (((4 1, 8 1, 4 8, 4 4, 1 4, 1 1, 4 1)))")
//@HivePdkUnitTests(
//		cases = {
//				@HivePdkUnitTest(
//						query = "SELECT ST_AsText(ST_Union(ST_Point(1.1, 2.2), ST_Point(3.3, 4.4))) FROM onerow",
//						result = "MULTIPOINT (1.1 2.2, 3.3 4.4)"
//						),
//				@HivePdkUnitTest(
//						query = "SELECT ST_AsText(ST_Union(ST_Polygon(1, 1, 1, 4, 4, 4, 4, 1), ST_Polygon(4,1, 4,8, 8,1))) FROM onerow",
//						result = "MULTIPOLYGON (((4 1, 8 1, 4 8, 4 4, 1 4, 1 1, 4 1)))"
//						),
//				@HivePdkUnitTest(
//						query = "SELECT ST_AsText(ST_Union(ST_Point(1.1, 2.2), ST_Point(3.3, 4.4), ST_Point(5.5, 6.6), ST_Point(1.1, 2.2))) FROM onerow",
//						result = "MULTIPOINT (1.1 2.2, 3.3 4.4, 5.5 6.6)"
//						)
//			}
//		)
public class ST_Union extends ST_GeometryProcessing
{		
	static final Log LOG = LogFactory.getLog(ST_Union.class.getName());
	
	public BytesWritable evaluate (BytesWritable ... geomrefs){
		// validate arguments
		if (geomrefs == null || geomrefs.length < 2){
			LogUtils.Log_VariableArgumentLength(LOG);
		}

		int firstWKID = 0;

		SpatialReference spatialRef = null;

		// validate spatial references and geometries first
		for (int i=0;i<geomrefs.length; i++){
			
			BytesWritable geomref = geomrefs[i];
			
			if (geomref == null || geomref.getLength() == 0){
				LogUtils.Log_ArgumentsNull(LOG);
				return null;
			}

			if (i==0){
				firstWKID = GeometryUtils.getWKID(geomref);
				if (firstWKID != GeometryUtils.WKID_UNKNOWN) {
					spatialRef = SpatialReference.create(firstWKID);
				}
			} else if (firstWKID != GeometryUtils.getWKID(geomref)){
				LogUtils.Log_SRIDMismatch(LOG, geomrefs[0], geomref);
				return null;
			}
		}
		
		// now build geometry array to pass to GeometryEngine.union
		Geometry [] geomsToUnion = new Geometry[geomrefs.length];
		
		for (int i=0;i<geomrefs.length;i++){
			//HiveGeometry hiveGeometry = GeometryUtils.geometryFromEsriShape(geomrefs[i]);
			OGCGeometry ogcGeometry = GeometryUtils.geometryFromEsriShape(geomrefs[i]);
			
			// if (i==0){   // get from ogcGeometry rather than re-create above?
			// 	spatialRef = hiveGeometry.spatialReference;
			// }
			
			if (ogcGeometry == null){
				LogUtils.Log_ArgumentsNull(LOG);
				return null;
			}
			
			geomsToUnion[i] = ogcGeometry.getEsriGeometry();
		}
		
		try {
			Geometry unioned = GeometryEngine.union(geomsToUnion, spatialRef);

			// we have to infer the type of the differenced geometry because we don't know
			// if it's going to end up as a single or multi-part geometry
			OGCType inferredType = GeometryUtils.getInferredOGCType(unioned);
			
			return GeometryUtils.geometryToEsriShapeBytesWritable(unioned, firstWKID, inferredType);
		} catch (Exception e){
			LogUtils.Log_ExceptionThrown(LOG, "GeometryEngine.union", e);
			return null;
		}
	}
}