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/*
* Copyright 2015 TouchType Ltd
*
* 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 io.github.spark_redshift_community.spark.redshift
import java.io.InputStreamReader
import java.net.URI
import com.amazonaws.auth.AWSCredentialsProvider
import com.amazonaws.services.s3.AmazonS3Client
import com.eclipsesource.json.Json
import io.github.spark_redshift_community.spark.redshift.Parameters.MergedParameters
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.catalyst.encoders.RowEncoder
import org.apache.spark.sql.sources._
import org.apache.spark.sql.types._
import org.apache.spark.sql.{DataFrame, Row, SQLContext, SaveMode}
import org.slf4j.LoggerFactory
import scala.collection.JavaConverters._
/**
* Data Source API implementation for Amazon Redshift database tables
*/
private[redshift] case class RedshiftRelation(
jdbcWrapper: JDBCWrapper,
s3ClientFactory: AWSCredentialsProvider => AmazonS3Client,
params: MergedParameters,
userSchema: Option[StructType])
(@transient val sqlContext: SQLContext)
extends BaseRelation
with PrunedFilteredScan
with InsertableRelation {
private val log = LoggerFactory.getLogger(getClass)
if (sqlContext != null) {
Utils.assertThatFileSystemIsNotS3BlockFileSystem(
new URI(params.rootTempDir), sqlContext.sparkContext.hadoopConfiguration)
}
private val tableNameOrSubquery =
params.query.map(q => s"($q)").orElse(params.table.map(_.toString)).get
override lazy val schema: StructType = {
userSchema.getOrElse {
val tableNameOrSubquery =
params.query.map(q => s"($q)").orElse(params.table.map(_.toString)).get
val conn = jdbcWrapper.getConnector(params.jdbcDriver, params.jdbcUrl, params.credentials)
try {
jdbcWrapper.resolveTable(conn, tableNameOrSubquery)
} finally {
conn.close()
}
}
}
override def toString: String = s"RedshiftRelation($tableNameOrSubquery)"
override def insert(data: DataFrame, overwrite: Boolean): Unit = {
val saveMode = if (overwrite) {
SaveMode.Overwrite
} else {
SaveMode.Append
}
val writer = new RedshiftWriter(jdbcWrapper, s3ClientFactory)
writer.saveToRedshift(sqlContext, data, saveMode, params)
}
override def unhandledFilters(filters: Array[Filter]): Array[Filter] = {
filters.filterNot(filter => FilterPushdown.buildFilterExpression(schema, filter).isDefined)
}
override def buildScan(requiredColumns: Array[String], filters: Array[Filter]): RDD[Row] = {
val creds = AWSCredentialsUtils.load(params, sqlContext.sparkContext.hadoopConfiguration)
for (
redshiftRegion <- Utils.getRegionForRedshiftCluster(params.jdbcUrl);
s3Region <- Utils.getRegionForS3Bucket(params.rootTempDir, s3ClientFactory(creds))
) {
if (redshiftRegion != s3Region) {
// We don't currently support `extraunloadoptions`, so even if Amazon _did_ add a `region`
// option for this we wouldn't be able to pass in the new option. However, we choose to
// err on the side of caution and don't throw an exception because we don't want to break
// existing workloads in case the region detection logic is wrong.
log.error("The Redshift cluster and S3 bucket are in different regions " +
s"($redshiftRegion and $s3Region, respectively). Redshift's UNLOAD command requires " +
s"that the Redshift cluster and Amazon S3 bucket be located in the same region, so " +
s"this read will fail.")
}
}
Utils.checkThatBucketHasObjectLifecycleConfiguration(params.rootTempDir, s3ClientFactory(creds))
if (requiredColumns.isEmpty) {
// In the special case where no columns were requested, issue a `count(*)` against Redshift
// rather than unloading data.
val whereClause = FilterPushdown.buildWhereClause(schema, filters)
val countQuery = s"SELECT count(*) FROM $tableNameOrSubquery $whereClause"
log.info(countQuery)
val conn = jdbcWrapper.getConnector(params.jdbcDriver, params.jdbcUrl, params.credentials)
try {
val results = jdbcWrapper.executeQueryInterruptibly(conn.prepareStatement(countQuery))
if (results.next()) {
val numRows = results.getLong(1)
val parallelism = sqlContext.getConf("spark.sql.shuffle.partitions", "200").toInt
val emptyRow = RowEncoder(StructType(Seq.empty)).toRow(Row(Seq.empty))
sqlContext.sparkContext
.parallelize(1L to numRows, parallelism)
.map(_ => emptyRow)
.asInstanceOf[RDD[Row]]
} else {
throw new IllegalStateException("Could not read count from Redshift")
}
} finally {
conn.close()
}
} else {
// Unload data from Redshift into a temporary directory in S3:
val tempDir = params.createPerQueryTempDir()
val unloadSql = buildUnloadStmt(requiredColumns, filters, tempDir, creds)
val conn = jdbcWrapper.getConnector(params.jdbcDriver, params.jdbcUrl, params.credentials)
try {
jdbcWrapper.executeInterruptibly(conn.prepareStatement(unloadSql))
} finally {
conn.close()
}
// Read the MANIFEST file to get the list of S3 part files that were written by Redshift.
// We need to use a manifest in order to guard against S3's eventually-consistent listings.
val filesToRead: Seq[String] = {
val cleanedTempDirUri =
Utils.fixS3Url(Utils.removeCredentialsFromURI(URI.create(tempDir)).toString)
val s3URI = Utils.createS3URI(cleanedTempDirUri)
val s3Client = s3ClientFactory(creds)
val is = s3Client.getObject(s3URI.getBucket, s3URI.getKey + "manifest").getObjectContent
val s3Files = try {
val entries = Json.parse(new InputStreamReader(is)).asObject().get("entries").asArray()
entries.iterator().asScala.map(_.asObject().get("url").asString()).toSeq
} finally {
is.close()
}
// The filenames in the manifest are of the form s3://bucket/key, without credentials.
// If the S3 credentials were originally specified in the tempdir's URI, then we need to
// reintroduce them here
s3Files.map { file =>
tempDir.stripSuffix("/") + '/' + file.stripPrefix(cleanedTempDirUri).stripPrefix("/")
}
}
val prunedSchema = pruneSchema(schema, requiredColumns)
sqlContext.read
.format(classOf[RedshiftFileFormat].getName)
.schema(prunedSchema)
.option("nullString", params.nullString)
.load(filesToRead: _*)
.queryExecution.executedPlan.execute().asInstanceOf[RDD[Row]]
}
}
override def needConversion: Boolean = false
private def buildUnloadStmt(
requiredColumns: Array[String],
filters: Array[Filter],
tempDir: String,
creds: AWSCredentialsProvider): String = {
assert(!requiredColumns.isEmpty)
// Always quote column names:
val columnList = requiredColumns.map(col => s""""$col"""").mkString(", ")
val whereClause = FilterPushdown.buildWhereClause(schema, filters)
val credsString: String =
AWSCredentialsUtils.getRedshiftCredentialsString(params, creds.getCredentials)
val query = {
// Since the query passed to UNLOAD will be enclosed in single quotes, we need to escape
// any backslashes and single quotes that appear in the query itself
val escapedTableNameOrSubqury = tableNameOrSubquery.replace("\\", "\\\\").replace("'", "\\'")
s"SELECT $columnList FROM $escapedTableNameOrSubqury $whereClause"
}
log.info(query)
// We need to remove S3 credentials from the unload path URI because they will conflict with
// the credentials passed via `credsString`.
val fixedUrl = Utils.fixS3Url(Utils.removeCredentialsFromURI(new URI(tempDir)).toString)
s"UNLOAD ('$query') TO '$fixedUrl' WITH CREDENTIALS '$credsString'" +
s" ESCAPE MANIFEST NULL AS '${params.nullString}'"
}
private def pruneSchema(schema: StructType, columns: Array[String]): StructType = {
val fieldMap = Map(schema.fields.map(x => x.name -> x): _*)
new StructType(columns.map(name => fieldMap(name)))
}
}
