sql/src/main/java/org/apache/druid/sql/calcite/expression/builtin/ArrayContainsOperatorConversion.java

/*
 * 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
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package org.apache.druid.sql.calcite.expression.builtin;

import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.sql.SqlFunction;
import org.apache.calcite.sql.type.OperandTypes;
import org.apache.calcite.sql.type.ReturnTypes;
import org.apache.calcite.sql.type.SqlTypeFamily;
import org.apache.druid.math.expr.Expr;
import org.apache.druid.math.expr.ExprEval;
import org.apache.druid.math.expr.Parser;
import org.apache.druid.query.filter.AndDimFilter;
import org.apache.druid.query.filter.DimFilter;
import org.apache.druid.segment.column.RowSignature;
import org.apache.druid.sql.calcite.expression.DruidExpression;
import org.apache.druid.sql.calcite.expression.Expressions;
import org.apache.druid.sql.calcite.expression.OperatorConversions;
import org.apache.druid.sql.calcite.planner.PlannerContext;
import org.apache.druid.sql.calcite.rel.VirtualColumnRegistry;

import javax.annotation.Nullable;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class ArrayContainsOperatorConversion extends BaseExpressionDimFilterOperatorConversion
{
  private static final String EXPR_FUNCTION = "array_contains";

  private static final SqlFunction SQL_FUNCTION = OperatorConversions
      .operatorBuilder("ARRAY_CONTAINS")
      .operandTypeChecker(
          OperandTypes.sequence(
              "(array,array)",
              OperandTypes.or(
                  OperandTypes.family(SqlTypeFamily.ARRAY),
                  OperandTypes.family(SqlTypeFamily.STRING)
              ),
              OperandTypes.or(
                  OperandTypes.family(SqlTypeFamily.ARRAY),
                  OperandTypes.family(SqlTypeFamily.STRING)
              )
          )
      )
      .returnTypeInference(ReturnTypes.BOOLEAN)
      .build();

  public ArrayContainsOperatorConversion()
  {
    super(SQL_FUNCTION, EXPR_FUNCTION);
  }

  @Nullable
  @Override
  public DimFilter toDruidFilter(
      final PlannerContext plannerContext,
      RowSignature rowSignature,
      @Nullable VirtualColumnRegistry virtualColumnRegistry,
      final RexNode rexNode
  )
  {
    final List<RexNode> operands = ((RexCall) rexNode).getOperands();
    final List<DruidExpression> druidExpressions = Expressions.toDruidExpressions(
        plannerContext,
        rowSignature,
        operands
    );
    if (druidExpressions == null) {
      return null;
    }

    // Converts array_contains() function into an AND of Selector filters if possible.
    final DruidExpression leftExpr = druidExpressions.get(0);
    final DruidExpression rightExpr = druidExpressions.get(1);

    if (leftExpr.isSimpleExtraction()) {
      Expr expr = Parser.parse(rightExpr.getExpression(), plannerContext.getExprMacroTable());
      // To convert this expression filter into an And of Selector filters, we need to extract all array elements.
      // For now, we can optimize only when rightExpr is a literal because there is no way to extract the array elements
      // by traversing the Expr. Note that all implementations of Expr are defined as package-private classes in a
      // different package.
      if (expr.isLiteral()) {
        // Evaluate the expression to get out the array elements.
        // We can safely pass a noop ObjectBinding if the expression is literal.
        ExprEval<?> exprEval = expr.eval(name -> null);
        String[] arrayElements = exprEval.asStringArray();
        if (arrayElements == null || arrayElements.length == 0) {
          // If arrayElements is empty which means rightExpr is an empty array,
          // it is technically more correct to return a TrueDimFiler here.
          // However, since both Calcite's SqlMultisetValueConstructor and Druid's ArrayConstructorFunction don't allow
          // to create an empty array with no argument, we just return null.
          return null;
        } else if (arrayElements.length == 1) {
          return newSelectorDimFilter(leftExpr.getSimpleExtraction(), arrayElements[0]);
        } else {
          final List<DimFilter> selectFilters = Arrays
              .stream(arrayElements)
              .map(val -> newSelectorDimFilter(leftExpr.getSimpleExtraction(), val))
              .collect(Collectors.toList());
          return new AndDimFilter(selectFilters);
        }
      }
    }
    return toExpressionFilter(plannerContext, getDruidFunctionName(), druidExpressions);
  }
}