ST_ConvexHull.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.hadoop.hive.GeometryUtils.OGCType;
import com.esri.core.geometry.ogc.OGCGeometry;

@Description(
	name = "ST_ConvexHull",
	value = "_FUNC_(ST_Geometry, ST_Geometry, ...) - returns an ST_Geometry as the convex hull of the supplied ST_Geometries",
	extended = "Example: SELECT ST_AsText(ST_ConvexHull(ST_Point(0, 0), ST_Point(0, 1), ST_Point(1, 1))) FROM onerow;\n" + 
		"MULTIPOLYGON (((0 0, 1 1, 0 1, 0 0)))")
//@HivePdkUnitTests(
//	cases = {
//		@HivePdkUnitTest(
//			query = "SELECT ST_AsText(ST_ConvexHull(ST_Point(0, 0), ST_Point(0, 1), ST_Point(1, 1))) FROM onerow",
//			result = "MULTIPOLYGON (((0 0, 1 1, 0 1, 0 0)))"
//			)
//		}
//	)

public class ST_ConvexHull extends ST_GeometryProcessing{
	
	static final Log LOG = LogFactory.getLog(ST_ConvexHull.class.getName());
	
	public BytesWritable evaluate (BytesWritable ... geomrefs){

		// validate arguments
		if (geomrefs == null || geomrefs.length < 1){
			// LogUtils.Log_VariableArgumentLength(LOG);
			return null;
		}

		int firstWKID = 0;
		
		// 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);
			} 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 [] geomsToProcess = 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 (ogcGeometry == null){
				LogUtils.Log_ArgumentsNull(LOG);
				return null;
			}
			
			geomsToProcess[i] = ogcGeometry.getEsriGeometry();
		}
		
		try {

  		    Geometry [] geomResult = GeometryEngine.convexHull(geomsToProcess, true);

  		    if (geomResult.length != 1){
  		    	return null;
  		    }
  		    
  		    Geometry merged = geomResult[0];
  		    
			// 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(merged);
			
			return GeometryUtils.geometryToEsriShapeBytesWritable(merged, firstWKID, inferredType);
		} catch (Exception e){
			LogUtils.Log_ExceptionThrown(LOG, "GeometryEngine.convexHull", e);
			return null;
		}
	}
}