[GitHub] [iceberg] massdosage commented on a change in pull request #1326: Hive: Filter pushdown

[GitBox <gi...@apache.org>]

massdosage commented on a change in pull request #1326:
URL: https://github.com/apache/iceberg/pull/1326#discussion_r472922327



##########
File path: mr/src/main/java/org/apache/iceberg/mr/hive/HiveIcebergFilterFactory.java
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@@ -0,0 +1,159 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.iceberg.mr.hive;
+
+import java.math.BigDecimal;
+import java.sql.Date;
+import java.sql.Timestamp;
+import java.util.List;
+import org.apache.hadoop.hive.ql.io.sarg.ExpressionTree;
+import org.apache.hadoop.hive.ql.io.sarg.PredicateLeaf;
+import org.apache.hadoop.hive.ql.io.sarg.SearchArgument;
+import org.apache.hadoop.hive.serde2.io.HiveDecimalWritable;
+import org.apache.iceberg.expressions.Expression;
+import org.apache.iceberg.expressions.Expressions;
+
+import static org.apache.iceberg.expressions.Expressions.and;
+import static org.apache.iceberg.expressions.Expressions.equal;
+import static org.apache.iceberg.expressions.Expressions.greaterThanOrEqual;
+import static org.apache.iceberg.expressions.Expressions.in;
+import static org.apache.iceberg.expressions.Expressions.isNull;
+import static org.apache.iceberg.expressions.Expressions.lessThan;
+import static org.apache.iceberg.expressions.Expressions.lessThanOrEqual;
+import static org.apache.iceberg.expressions.Expressions.not;
+import static org.apache.iceberg.expressions.Expressions.or;
+
+
+public class HiveIcebergFilterFactory {
+
+  private static final int MICROS_PER_SECOND = 1000000;
+  private static final int NANOSECS_PER_MICROSEC = 1000;
+
+  private HiveIcebergFilterFactory() {}
+
+  public static Expression generateFilterExpression(SearchArgument sarg) {
+    return translate(sarg.getExpression(), sarg.getLeaves());
+  }
+
+  /**
+   * Recursive method to traverse down the ExpressionTree to evaluate each expression and its leaf nodes.
+   * @param tree Current ExpressionTree where the 'top' node is being evaluated.
+   * @param leaves List of all leaf nodes within the tree.
+   * @return Expression that is translated from the Hive SearchArgument.
+   */
+  private static Expression translate(ExpressionTree tree, List<PredicateLeaf> leaves) {
+    List<ExpressionTree> childNodes = tree.getChildren();
+    switch (tree.getOperator()) {
+      case OR:
+        Expression orResult = Expressions.alwaysFalse();
+        for (ExpressionTree child : childNodes) {
+          orResult = or(orResult, translate(child, leaves));
+        }
+        return orResult;
+      case AND:
+        Expression result = Expressions.alwaysTrue();
+        for (ExpressionTree child : childNodes) {
+          result = and(result, translate(child, leaves));
+        }
+        return result;
+      case NOT:
+        return not(translate(childNodes.get(0), leaves));
+      case LEAF:
+        return translateLeaf(leaves.get(tree.getLeaf()));
+      case CONSTANT:
+        throw new UnsupportedOperationException("CONSTANT operator is not supported");
+      default:
+        throw new IllegalStateException("Unknown operator: " + tree.getOperator());
+    }
+  }
+
+  /**
+   * Translate leaf nodes from Hive operator to Iceberg operator.
+   * @param leaf Leaf node
+   * @return Expression fully translated from Hive PredicateLeaf
+   */
+  private static Expression translateLeaf(PredicateLeaf leaf) {
+    String column = leaf.getColumnName();
+    switch (leaf.getOperator()) {
+      case EQUALS:
+        return equal(column, leafToLiteral(leaf));

Review comment:
       > seems like leafToLiteral can be called only once and its result used in the switch branches
   
   But `leafToLiteral` isn't used in all the switch branches (e.g. `IN` and `BETWEEN` use uses `leafToLiteralList`, `IS_NULL` doesn't use it at all) so we'd be calling it for nothing in those cases. I think it's fine as is?




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