[GitHub] [iceberg] openinx commented on a change in pull request #1893: Flink: Support filter pushdown in IcebergTableSource

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

openinx commented on a change in pull request #1893:
URL: https://github.com/apache/iceberg/pull/1893#discussion_r547962504



##########
File path: flink/src/main/java/org/apache/iceberg/flink/FlinkFilters.java
##########
@@ -0,0 +1,183 @@
+/*
+ * 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.flink;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+import org.apache.flink.table.expressions.CallExpression;
+import org.apache.flink.table.expressions.FieldReferenceExpression;
+import org.apache.flink.table.expressions.ResolvedExpression;
+import org.apache.flink.table.expressions.ValueLiteralExpression;
+import org.apache.flink.table.functions.BuiltInFunctionDefinition;
+import org.apache.flink.table.functions.BuiltInFunctionDefinitions;
+import org.apache.iceberg.expressions.Expression;
+import org.apache.iceberg.expressions.Expression.Operation;
+import org.apache.iceberg.expressions.Expressions;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableMap;
+import org.apache.iceberg.util.NaNUtil;
+
+public class FlinkFilters {
+  private FlinkFilters() {
+  }
+
+  private static final Map<BuiltInFunctionDefinition, Operation> FILTERS = ImmutableMap
+      .<BuiltInFunctionDefinition, Operation>builder()
+      .put(BuiltInFunctionDefinitions.EQUALS, Operation.EQ)
+      .put(BuiltInFunctionDefinitions.NOT_EQUALS, Operation.NOT_EQ)
+      .put(BuiltInFunctionDefinitions.GREATER_THAN, Operation.GT)
+      .put(BuiltInFunctionDefinitions.GREATER_THAN_OR_EQUAL, Operation.GT_EQ)
+      .put(BuiltInFunctionDefinitions.LESS_THAN, Operation.LT)
+      .put(BuiltInFunctionDefinitions.LESS_THAN_OR_EQUAL, Operation.LT_EQ)
+      .put(BuiltInFunctionDefinitions.IN, Operation.IN)
+      .put(BuiltInFunctionDefinitions.IS_NULL, Operation.IS_NULL)
+      .put(BuiltInFunctionDefinitions.IS_NOT_NULL, Operation.NOT_NULL)
+      .put(BuiltInFunctionDefinitions.AND, Operation.AND)
+      .put(BuiltInFunctionDefinitions.OR, Operation.OR)
+      .put(BuiltInFunctionDefinitions.NOT, Operation.NOT)
+      .build();
+
+
+  public static Optional<Expression> convert(org.apache.flink.table.expressions.Expression flinkExpression) {
+    if (!(flinkExpression instanceof CallExpression)) {
+      return Optional.empty();
+    }
+
+    CallExpression call = (CallExpression) flinkExpression;
+    Operation op = FILTERS.get(call.getFunctionDefinition());
+    if (op != null) {
+      switch (op) {
+        case IS_NULL:
+          FieldReferenceExpression isNullFilter = (FieldReferenceExpression) call.getResolvedChildren().get(0);
+          return Optional.of(Expressions.isNull(isNullFilter.getName()));
+
+        case NOT_NULL:
+          FieldReferenceExpression notNullExpression = (FieldReferenceExpression) call.getResolvedChildren().get(0);
+          return Optional.of(Expressions.notNull(notNullExpression.getName()));
+
+        case LT:
+          return convertComparisonExpression(Expressions::lessThan, call);
+
+        case LT_EQ:
+          return convertComparisonExpression(Expressions::lessThanOrEqual, call);
+
+        case GT:
+          return convertComparisonExpression(Expressions::greaterThan, call);
+
+        case GT_EQ:
+          return convertComparisonExpression(Expressions::greaterThanOrEqual, call);
+
+        case EQ:
+          return convertComparisonExpression(Expressions::equal, call);
+
+        case NOT_EQ:
+          return convertComparisonExpression(Expressions::notEqual, call);
+
+        case IN:
+          List<ResolvedExpression> args = call.getResolvedChildren();
+          FieldReferenceExpression field = (FieldReferenceExpression) args.get(0);
+          List<ResolvedExpression> values = args.subList(1, args.size());
+
+          List<Object> inputValues = values.stream().filter(
+              expression -> {
+                if (expression instanceof ValueLiteralExpression) {
+                  return !((ValueLiteralExpression) flinkExpression).isNull();
+                }
+
+                return false;
+              }
+          ).map(expression -> {
+            ValueLiteralExpression valueLiteralExpression = (ValueLiteralExpression) expression;
+            return valueLiteralExpression.getValueAs(valueLiteralExpression.getOutputDataType().getConversionClass())
+                .get();
+          }).collect(Collectors.toList());
+          return Optional.of(Expressions.in(field.getName(), inputValues));
+
+        case NOT:
+          Optional<Expression> child = convert(call.getResolvedChildren().get(0));
+          if (child.isPresent()) {
+            return Optional.of(Expressions.not(child.get()));
+          }
+
+          return Optional.empty();
+
+        case AND: {
+          return convertLogicExpression(Expressions::and, call);
+        }
+
+        case OR: {
+          return convertLogicExpression(Expressions::or, call);
+        }
+      }
+    }
+
+    return Optional.empty();
+  }
+
+  private static Optional<Expression> convertLogicExpression(BiFunction<Expression, Expression, Expression> function,
+                                                             CallExpression call) {
+    List<ResolvedExpression> args = call.getResolvedChildren();
+    Optional<Expression> left = convert(args.get(0));
+    Optional<Expression> right = convert(args.get(1));
+    if (left.isPresent() && right.isPresent()) {
+      return Optional.of(function.apply(left.get(), right.get()));
+    }
+
+    return Optional.empty();
+  }
+
+  private static Optional<Expression> convertComparisonExpression(BiFunction<String, Object, Expression> function,
+                                                                  CallExpression call) {
+    List<ResolvedExpression> args = call.getResolvedChildren();
+    FieldReferenceExpression fieldReferenceExpression;
+    ValueLiteralExpression valueLiteralExpression;
+    if (literalOnRight(args)) {
+      fieldReferenceExpression = (FieldReferenceExpression) args.get(0);
+      valueLiteralExpression = (ValueLiteralExpression) args.get(1);
+    } else {

Review comment:
       Q:  is it possible that we have two literals in both left and right side ? For example,  someone may write the SQL: 
   `SELECT * FROM test where 1 > 0`,  then we could not think that the left MUST be a field and the right MUST be a `value` in this `else` block.   
   
   We have done the similar work in our own branch before,  you could see the PR: https://github.com/generic-datalake/iceberg-poc/pull/2/files#diff-86160616589acf1dd526b10b73418a46fe60f9e5e5ab6946a4ea3c8f019542f5R123




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