Package org.apache.drill.exec.planner.common

Class CountToDirectScanUtils

java.lang.Object
org.apache.drill.exec.planner.common.CountToDirectScanUtils
public class CountToDirectScanUtils extends Object
A utility class that contains helper functions used by rules that convert COUNT(*) and COUNT(col) aggregates (no group-by) to DirectScan

  • Constructor Details

    • CountToDirectScanUtils

      public CountToDirectScanUtils()

  • Method Details

    • containsStarOrNotNullInput

      public static boolean containsStarOrNotNullInput(org.apache.calcite.rel.core.AggregateCall aggregateCall, org.apache.calcite.rel.core.Aggregate aggregate)
      Checks if aggregate call contains star or non-null expression: 
       count(*)  == >  empty arg  ==>  rowCount
 count(Not-null-input) ==> rowCount
      Parameters:
      aggregateCall - aggregate call
      aggregate - aggregate relation expression
      Returns:
      true of aggregate call contains star or non-null expression

    • constructDataType

      public static org.apache.calcite.rel.type.RelDataType constructDataType(org.apache.calcite.rel.core.Aggregate aggregateRel, Collection<String> fieldNames)
      For each aggregate call creates field based on its name with bigint type. Constructs record type for created fields.
      Parameters:
      aggregateRel - aggregate relation expression
      fieldNames - field names
      Returns:
      record type

    • buildSchema

      public static LinkedHashMap<String,Class<?>> buildSchema(List<String> fieldNames)
      Builds schema based on given field names. Type for each schema is set to long.class.
      Parameters:
      fieldNames - field names
      Returns:
      schema

    • prepareFieldExpressions

      public static List<org.apache.calcite.rex.RexNode> prepareFieldExpressions(org.apache.calcite.rel.type.RelDataType rowType)
      For each field creates row expression.
      Parameters:
      rowType - row type
      Returns:
      list of row expressions