From 6eaaa49faa14e49bc81b7b4a9520f26238185c9b Mon Sep 17 00:00:00 2001
From: Karel Maesen <karel@geovise.com>
Date: Sun, 12 Aug 2018 17:08:06 +0200
Subject: [PATCH] HHH-12608 Support for ST_Dwithin() in DB2

---
 .../dialect/db2/DB2SpatialDialect.java        | 28 ++++++++++++++++++-
 .../dialects/db2/DB2ExpectationsFactory.java  |  2 +-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/hibernate-spatial/src/main/java/org/hibernate/spatial/dialect/db2/DB2SpatialDialect.java b/hibernate-spatial/src/main/java/org/hibernate/spatial/dialect/db2/DB2SpatialDialect.java
index 1e1afc6d50..263b946efd 100644
--- a/hibernate-spatial/src/main/java/org/hibernate/spatial/dialect/db2/DB2SpatialDialect.java
+++ b/hibernate-spatial/src/main/java/org/hibernate/spatial/dialect/db2/DB2SpatialDialect.java
@@ -7,6 +7,7 @@
 package org.hibernate.spatial.dialect.db2;
 
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.hibernate.HibernateException;
@@ -14,6 +15,7 @@
 import org.hibernate.dialect.DB2Dialect;
 import org.hibernate.dialect.function.StandardSQLFunction;
 import org.hibernate.engine.config.spi.ConfigurationService;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.spatial.GeolatteGeometryJavaTypeDescriptor;
 import org.hibernate.spatial.GeolatteGeometryType;
@@ -25,6 +27,9 @@
 import org.hibernate.spatial.SpatialFunction;
 import org.hibernate.spatial.SpatialRelation;
 import org.hibernate.type.StandardBasicTypes;
+import org.hibernate.type.Type;
+
+import static java.lang.String.format;
 
 /**
  * @author David Adler, Adtech Geospatial
@@ -223,6 +228,7 @@ private void registerSpatialFunctions() {
 		) );
 
 		// Register non-SFS functions listed in Hibernate Spatial
+		registerFunction( "dwithin", new DWithinFunction());
 
 //		// The srid parameter needs to be explicitly cast to INTEGER to avoid a -245 SQLCODE,
 //		// ambiguous parameter.
@@ -244,7 +250,7 @@ private void registerSpatialFunctions() {
 
 	@Override
 	public String getDWithinSQL(String columnName) {
-		return "db2gse.ST_Distance(" + columnName + ",?) < ?";
+		return "db2gse.ST_Intersects(" + columnName + ", db2gse.ST_Buffer(?, ?, 'METER')) = 1";
 	}
 
 	@Override
@@ -317,4 +323,24 @@ public boolean supports(SpatialFunction function) {
 	public boolean supportsFiltering() {
 		return false;
 	}
+
+
+	private static class DWithinFunction extends StandardSQLFunction {
+
+		public DWithinFunction() {
+			super( "db2gse.ST_Dwithin" , StandardBasicTypes.NUMERIC_BOOLEAN);
+		}
+
+		public String render(Type firstArgumentType, final List args, final SessionFactoryImplementor factory) {
+			StringBuilder sb = new StringBuilder( "db2gse.ST_Intersects( " );
+			sb.append( (String)args.get(0) ) //
+					.append(", db2gse.ST_Buffer(")
+					.append((String)args.get(1) )
+					.append(", ")
+					.append((String)args.get(2) )
+					.append(", 'METER'))");
+			return sb.toString();
+		}
+
+	}
 }
diff --git a/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/dialects/db2/DB2ExpectationsFactory.java b/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/dialects/db2/DB2ExpectationsFactory.java
index e90d3b03c9..c23873824e 100644
--- a/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/dialects/db2/DB2ExpectationsFactory.java
+++ b/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/dialects/db2/DB2ExpectationsFactory.java
@@ -88,7 +88,7 @@ protected NativeSQLStatement createNativeRelateStatement(Geometry geom, String m
 
 	@Override
 	protected NativeSQLStatement createNativeDwithinStatement(Point geom, double distance) {
-		String sql = "select t.id, DB2GSE.ST_dwithin(t.geom, DB2GSE.ST_GeomFromText(?, 4326), " + distance + " ) from GeomTest t where DB2GSE.ST_dwithin(t.geom, DB2GSE.ST_GeomFromText(?, 4326), " + distance + ") = 1 and db2gse.st_srid(t.geom) = 4326";
+		String sql = "select t.id, DB2GSE.ST_dwithin(DB2GSE.ST_GeomFromText(?, 4326), t.geom, " + distance + " , 'METER') from GeomTest t where DB2GSE.ST_dwithin(DB2GSE.ST_GeomFromText(?, 4326), t.geom,  " + distance + ", 'METER') = 1 and db2gse.st_srid(t.geom) = 4326";
 		return createNativeSQLStatementAllWKTParams( sql, geom.toText() );
 	}