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

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query engine core source code

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// 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.description.Row
import com.typesafe.scalalogging.slf4j.LazyLogging
import com.twitter.concurrent.Spool
import com.twitter.util.Future

object QueryableSource extends LazyLogging {
  
  /**
   * copied from com.twitter.storehaus.IterableStore, but removed tuple dependency
   */
  def iteratorToSpool[V](it: Iterator[V], transformer: (V) => Row): Future[Spool[Row]] = Future.value {
    if (it.hasNext) {
      // *:: for lazy/deferred tail
      val next = it.next
      transformer(next) *:: iteratorToSpool(it, transformer)
    } else {
      Spool.empty
    }
  }
}