scray.querying.source.queryColumnDispenserSources.scala Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of scray-querying Show documentation
query engine core source code
There is a newer version: 1.1.2
// See the LICENCE.txt file distributed with this work for additional
// information regarding copyright ownership.
//
// Licensed 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 scray.querying.source

import scray.querying.queries.DomainQuery
import scray.querying.description.{Column, Row, RowColumn, SimpleRow}
import scray.querying.caching.Cache
import scray.querying.caching.NullCache
import scala.collection.mutable.HashSet
import scala.collection.mutable.ArrayBuffer
import scala.util.Try
import com.typesafe.scalalogging.slf4j.LazyLogging

object ColumnDispenserTransformer {
  def transformElement[Q <: DomainQuery](element: Row, query: Q, columns: HashSet[Column]): Row = {
    // if we find a column which is not requested by this query we will dispense it
    element.intersectValues(columns)
  }
}

/**
 * used to filter columns according to the query parameters supplied,
 * i.e. throw away columns which are not needed any more
 */
class LazyQueryColumnDispenserSource[Q <: DomainQuery](source: LazySource[Q]) 
  extends LazyQueryMappingSource[Q](source) with LazyLogging {

  private val queryColumns = new HashSet[Column]
  
  override def init(query: Q) = {
    queryColumns.clear
    queryColumns ++= query.getResultSetColumns
  } 
  
  def transformSpoolElement(element: Row, query: Q): Row = 
    ColumnDispenserTransformer.transformElement(element, query, queryColumns)

  /**
   * This is the maximum we can return, if a query will request them all
   */
  override def getColumns: Set[Column] = source.getColumns
  
  override def getDiscriminant = "ColumnDispenser" + source.getDiscriminant
}


/**
 * used to filter rows according to the domain parameters supplied
 */
class EagerCollectingColumnDispenserSource[Q <: DomainQuery, R](source: Source[Q, R]) 
  extends EagerCollectingQueryMappingSource[Q, R](source) with LazyLogging {

  private val queryColumns = new HashSet[Column]
  
  override def init(query: Q) = {
    queryColumns.clear
    queryColumns ++= query.getResultSetColumns
  }
  
  override def transformSeqElement(element: Row, query: Q): Row = 
    ColumnDispenserTransformer.transformElement(element, query, queryColumns)

  override def getColumns: Set[Column] = source.getColumns
  
  override def getDiscriminant = "ColumnDispenser" + source.getDiscriminant
}