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    Object Storage Service:Accelerate Spark data queries by using OSS Select

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    Object Storage Service:Accelerate Spark data queries by using OSS Select

    Last Updated:Jun 21, 2026

    This topic describes how to configure Spark to use OSS Select to accelerate data queries and explains the performance benefits.

    Background

    All operations in this topic are based on a CDH6 cluster configured as described in Process OSS data by using Apache Impala (CDH6).

    Note

    The content enclosed in ${} is an environment variable. Please replace it with a value from your actual environment.

    Step 1: Configure Spark to read and write OSS

    To enable Spark to read from and write to OSS, you must complete the following steps on all CDH nodes:

    1. Go to the ${CDH_HOME}/lib/spark directory and run the following commands: 

      [root@cdh-master spark]# cd jars/
[root@cdh-master jars]# ln -s ../../../jars/hadoop-aliyun-3.0.0-cdh6.0.1.jar hadoop-aliyun.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-sdk-oss-2.8.3.jar aliyun-sdk-oss-2.8.3.jar
[root@cdh-master jars]# ln -s ../../../jars/jdom-1.1.jar jdom-1.1.jar

    2. Go to the ${CDH_HOME}/lib/spark directory and start a Spark shell to verify the configuration. 

      [root@cdh-master spark]# ./bin/spark-shell
WARNING: User-defined SPARK_HOME (/opt/cloudera/parcels/CDH-6.0.1-1.cdh6.0.1.p0.590678/lib/spark) overrides detected (/opt/cloudera/parcels/CDH/lib/spark).
WARNING: Running spark-class from user-defined location.
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
Spark context Web UI available at http://x.x.x.x:4040
Spark context available as 'sc' (master = yarn, app id = application_1540878848110_0004).
Spark session available as'spark'.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 2.2.0-cdh6.0.1
      /_/
Using Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_152)
Type in expressions to have them evaluated.
Type :help for more information.
scala> val myfile = sc.textFile("oss://{your-bucket-name}/50/store_sales")
myfile: org.apache.spark.rdd.RDD[String] = oss://{your-bucket-name}/50/store_sales MapPartitionsRDD[1] at textFile at <console>:24
scala> myfile.count()
res0: Long = 144004764
scala> myfile.map(line => line.split('|')).filter(_(0).toInt >= 2451262).take(3)
res15: Array[Array[String]] = Array(Array(2451262, 71079, 20359, 154660, 284233, 6206, 150579, 46, 512, 2160001, 84, 6.94, 11.38, 9.33, 681.83, 783.72, 582.96, 955.92, 5.09, 681.83, 101.89, 106.98, -481.07), Array(2451262, 71079, 26863, 154660, 284233, 6206, 150579, 46, 345, 2160001, 12, 67.82, 115.29, 25.36, 0.00, 304.32, 813.84, 1383.48, 21.30, 0.00, 304.32, 325.62, -509.52), Array(2451262, 71079, 55852, 154660, 284233, 6206, 150579, 46, 243, 2160001, 74, 32.41, 34.67, 1.38, 0.00, 102.12, 2398.34, 2565.58, 4.08, 0.00, 102.12, 106.20, -2296.22))
scala> myfile.map(line => line.split('|')).filter(_(0) >= "2451262").saveAsTextFile("oss://{your-bucket-name}/spark-oss-test.1")

      If the commands execute successfully, the configuration is correct.

    Step 2: Configure Spark to support OSS Select

    For more information about OSS Select, see OSS Select. The following examples use the oss-cn-shenzhen.aliyuncs.com endpoint, which is in the China (Shenzhen) region. Complete the following steps on all CDH nodes:

    1. Download the Spark support package for OSS Select, spark-2.2.0-oss-select-0.1.0-SNAPSHOT.tar.gz, to the ${CDH_HOME}/jars directory. This package is a preview release.

    2. Decompress the package.

      [root@cdh-master jars]# tar -tvf spark-2.2.0-oss-select-0.1.0-SNAPSHOT.tar.gz 
drwxr-xr-x root/root 0 2018-10-30 17:59 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/
-rw-r--r-- root/root 26514 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/stax-api-1.0.1.jar
-rw-r--r-- root/root 547584 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-sdk-oss-3.3.0.jar
-rw-r--r-- root/root 13277 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-java-sdk-sts-3.0.0.jar
-rw-r--r-- root/root 116337 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-java-sdk-core-3.4.0.jar
-rw-r--r-- root/root 215492 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-java-sdk-ram-3.0.0.jar
-rw-r--r-- root/root 67758 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/jettison-1.1.jar
-rw-r--r-- root/root 57264 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/json-20170516.jar
-rw-r--r-- root/root 890168 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/jaxb-impl-2.2.3-1.jar
-rw-r--r-- root/root 458739 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/jersey-core-1.9.jar
-rw-r--r-- root/root 147952 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/jersey-json-1.9.jar
-rw-r--r-- root/root 788137 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-java-sdk-ecs-4.2.0.jar
-rw-r--r-- root/root 153115 2018-10-30 16:11 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/jdom-1.1.jar
-rw-r--r-- root/root 65437 2018-10-31 14:41 spark-2.2.0-oss-select-0.1.0-SNAPSHOT/aliyun-oss-select-spark_2.11-0.1.0-SNAPSHOT.jar

    3. Go to the ${CDH_HOME}/lib/spark/jars directory and run the following commands: 

      [root@cdh-master jars]# pwd
/opt/cloudera/parcels/CDH/lib/spark/jars
[root@cdh-master jars]# rm -f aliyun-sdk-oss-2.8.3.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-oss-select-spark_2.11-0.1.0-SNAPSHOT.jar aliyun-oss-select-spark_2.11-0.1.0-SNAPSHOT.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-java-sdk-core-3.4.0.jar aliyun-java-sdk-core-3.4.0.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-java-sdk-ecs-4.2.0.jar aliyun-java-sdk-ecs-4.2.0.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-java-sdk-ram-3.0.0.jar aliyun-java-sdk-ram-3.0.0.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-java-sdk-sts-3.0.0.jar aliyun-java-sdk-sts-3.0.0.jar
[root@cdh-master jars]# ln -s ../../../jars/aliyun-sdk-oss-3.3.0.jar aliyun-sdk-oss-3.3.0.jar
[root@cdh-master jars]# ln -s ../../../jars/jdom-1.1.jar jdom-1.1.jar

    Comparison test

    Test environment: The comparison test runs on a Spark on YARN cluster. The cluster has four Node Manager nodes. Each node supports up to four containers, and each container is allocated one vCPU and 2 GB of memory.

    Test data: A 630 MB dataset with three columns: name, company, and age.

    [root@cdh-master jars]# hadoop fs -ls oss://select-test-sz/people/
Found 10 items
-rw-rw-rw-   1   63079930 2018-10-30 17:03 oss://select-test-sz/people/part-00000
-rw-rw-rw-   1   63079930 2018-10-30 17:03 oss://select-test-sz/people/part-00001
-rw-rw-rw-   1   63079930 2018-10-30 17:05 oss://select-test-sz/people/part-00002
-rw-rw-rw-   1   63079930 2018-10-30 17:05 oss://select-test-sz/people/part-00003
-rw-rw-rw-   1   63079930 2018-10-30 17:06 oss://select-test-sz/people/part-00004
-rw-rw-rw-   1   63079930 2018-10-30 17:12 oss://select-test-sz/people/part-00005
-rw-rw-rw-   1   63079930 2018-10-30 17:14 oss://select-test-sz/people/part-00006
-rw-rw-rw-   1   63079930 2018-10-30 17:14 oss://select-test-sz/people/part-00007
-rw-rw-rw-   1   63079930 2018-10-30 17:15 oss://select-test-sz/people/part-00008
-rw-rw-rw-   1   63079930 2018-10-30 17:16 oss://select-test-sz/people/part-00009

    Go to the ${CDH_HOME}/lib/spark/ directory and start spark-shell. Then, run two queries for comparison: one with OSS Select and one without. 

    [root@cdh-master spark]# ./bin/spark-shell
WARNING: User-defined SPARK_HOME (/opt/cloudera/parcels/CDH-6.0.1-1.cdh6.0.1.p0.590678/lib/spark) overrides detected (/opt/cloudera/parcels/CDH/lib/spark).
WARNING: Running spark-class from user-defined location.
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
Spark context Web UI available at http://x.x.x.x:4040
Spark context available as 'sc' (master = yarn, app id = application_1540887123331_0008).
Spark session available as 'spark'.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 2.2.0-cdh6.0.1
      /_/
Using Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_152)
Type in expressions to have them evaluated.
Type :help for more information.
scala> val sqlContext = spark.sqlContext
sqlContext: org.apache.spark.sql.SQLContext = org.apache.spark.sql.SQLContext@4bdef487
scala> sqlContext.sql("CREATE TEMPORARY VIEW people USING com.aliyun.oss " +
     |   "OPTIONS (" +
     |   "oss.bucket 'select-test-sz', " +
     |   "oss.prefix 'people', " + // objects with this prefix belong to this table
     |   "oss.schema 'name string, company string, age long'," + // like 'column_a long, column_b string'
     |   "oss.data.format 'csv'," + // we only support csv now
     |   "oss.input.csv.header 'None'," +
     |   "oss.input.csv.recordDelimiter '\r\n'," +
     |   "oss.input.csv.fieldDelimiter ','," +
     |   "oss.input.csv.commentChar '#'," +
     |   "oss.input.csv.quoteChar '\"'," +
     |   "oss.output.csv.recordDelimiter '\n'," +
     |   "oss.output.csv.fieldDelimiter ','," +
     |   "oss.output.csv.quoteChar '\"'," +
     |   "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " +
     |   "oss.accessKeyId 'Your Access Key Id', " +
     |   "oss.accessKeySecret 'Your Access Key Secret')")
res0: org.apache.spark.sql.DataFrame = []
scala>   val sql: String = "select count(*) from people where name like 'Lora%'"
sql: String = select count(*) from people where name like 'Lora%'
scala>   sqlContext.sql(sql).show()
+--------+
|count(1)|
+--------+
|   31770|
+--------+
scala> val textFile = sc.textFile("oss://select-test-sz/people/")
textFile: org.apache.spark.rdd.RDD[String] = oss://select-test-sz/people/ MapPartitionsRDD[8] at textFile at <console>:24
scala> textFile.map(line => line.split(',')).filter(_(0).startsWith("Lora")).count()
res3: Long = 31770

    The results show a significant performance improvement when using OSS Select. The query with OSS Select takes 15 seconds, while the query without it takes 54 seconds.

    Implementation of the OSS Select support package (Preview)

    Spark integrates with OSS Select by extending its DataSource API. The support package implements PrunedFilteredScan to push down required columns and filter conditions to OSS Select for execution. This support package is still under development. The following sections describe the current specifications and supported filter conditions.

    • Specifications: 

      scala> sqlContext.sql("CREATE TEMPORARY VIEW people USING com.aliyun.oss " +
     |   "OPTIONS (" +
     |   "oss.bucket 'select-test-sz', " +
     |   "oss.prefix 'people', " + // objects with this prefix belong to this table
     |   "oss.schema 'name string, company string, age long'," + // like 'column_a long, column_b string'
     |   "oss.data.format 'csv'," + // we only support csv now
     |   "oss.input.csv.header 'None'," +
     |   "oss.input.csv.recordDelimiter '\r\n'," +
     |   "oss.input.csv.fieldDelimiter ','," +
     |   "oss.input.csv.commentChar '#'," +
     |   "oss.input.csv.quoteChar '\"'," +
     |   "oss.output.csv.recordDelimiter '\n'," +
     |   "oss.output.csv.fieldDelimiter ','," +
     |   "oss.output.csv.quoteChar '\"'," +
     |   "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " +
     |   "oss.accessKeyId 'Your Access Key Id', " +
     |   "oss.accessKeySecret 'Your Access Key Secret')")

      Parameter

      Description

      oss.bucket

      The bucket where your data is stored.

      oss.prefix

      All objects with this prefix belong to the defined TEMPORARY VIEW.

      oss.schema

      The schema for the TEMPORARY VIEW. Currently, you specify the schema as a string. Future versions will support specifying it from a file.

      oss.data.format

      The format of the data. Only the CSV format is currently supported. Support for other formats will be added in future versions.

      oss.input.csv.*

      The CSV input format parameters.

      oss.output.csv.*

      The CSV output format parameters.

      oss.endpoint

      The endpoint of the bucket's region.

      oss.accessKeyId

      Your AccessKey ID.

      oss.accessKeySecret

      Your AccessKey Secret.
      Note

      This section defines only basic parameters. For a complete list, see SelectObject.

    • Supported filter conditions: =,<,>,<=, >=,||,or,not,and,in,like(StringStartsWith,StringEndsWith,StringContains). For filter conditions that cannot be pushed down, such as arithmetic operations and string concatenation, which cannot be retrieved by PrunedFilteredScan, only the required columns are pushed down to OSS Select.

      Note

      OSS Select also supports other filter conditions. For more information, see SelectObject.

    TPC-H query comparison

    To further verify the performance benefits, this test compares the query performance on the 'lineitem' table by using 'query1.sql' from the TPC-H benchmark. To ensure that OSS Select filters a larger amount of data, the test modifies the 'WHERE' clause from l_shipdate <= '1998-09-16' to l_shipdate > '1997-09-16'. The test dataset is 2.27 GB. The test compares the following methods:

    • Using only Spark SQL 

      [root@cdh-master jar]# hadoop fs -ls oss://select-test-sz/data/lineitem.csv
-rw-rw-rw-   1 2441079322 2018-10-31 11:18 oss://select-test-sz/data/lineitem.csv

    • Using Spark SQL with OSS Select 

      scala> import org.apache.spark.sql.types.{IntegerType, LongType, StringType, StructField, StructType, DoubleType}
import org.apache.spark.sql.types.{IntegerType, LongType, StringType, StructField, StructType, DoubleType}
scala> import org.apache.spark.sql.{Row, SQLContext}
import org.apache.spark.sql.{Row, SQLContext}
scala> val sqlContext = spark.sqlContext
sqlContext: org.apache.spark.sql.SQLContext = org.apache.spark.sql.SQLContext@74e2cfc5
scala> val textFile = sc.textFile("oss://select-test-sz/data/lineitem.csv")
textFile: org.apache.spark.rdd.RDD[String] = oss://select-test-sz/data/lineitem.csv MapPartitionsRDD[1] at textFile at <console>:26
scala> val dataRdd = textFile.map(_.split('|'))
dataRdd: org.apache.spark.rdd.RDD[Array[String]] = MapPartitionsRDD[2] at map at <console>:28
scala> val schema = StructType(
     |     List(
     |         StructField("L_ORDERKEY",LongType,true),
     |         StructField("L_PARTKEY",LongType,true),
     |         StructField("L_SUPPKEY",LongType,true),
     |         StructField("L_LINENUMBER",IntegerType,true),
     |         StructField("L_QUANTITY",DoubleType,true),
     |         StructField("L_EXTENDEDPRICE",DoubleType,true),
     |         StructField("L_DISCOUNT",DoubleType,true),
     |         StructField("L_TAX",DoubleType,true),
     |         StructField("L_RETURNFLAG",StringType,true),
     |         StructField("L_LINESTATUS",StringType,true),
     |         StructField("L_SHIPDATE",StringType,true),
     |         StructField("L_COMMITDATE",StringType,true),
     |         StructField("L_RECEIPTDATE",StringType,true),
     |         StructField("L_SHIPINSTRUCT",StringType,true),
     |         StructField("L_SHIPMODE",StringType,true),
     |         StructField("L_COMMENT",StringType,true)
     |     )
     | )
schema: org.apache.spark.sql.types.StructType = StructType(StructField(L_ORDERKEY,LongType,true), StructField(L_PARTKEY,LongType,true), StructField(L_SUPPKEY,LongType,true), StructField(L_LINENUMBER,IntegerType,true), StructField(L_QUANTITY,DoubleType,true), StructField(L_EXTENDEDPRICE,DoubleType,true), StructField(L_DISCOUNT,DoubleType,true), StructField(L_TAX,DoubleType,true), StructField(L_RETURNFLAG,StringType,true), StructField(L_LINESTATUS,StringType,true), StructField(L_SHIPDATE,StringType,true), StructField(L_COMMITDATE,StringType,true), StructField(L_RECEIPTDATE,StringType,true), StructField(L_SHIPINSTRUCT,StringType,true), StructField(L_SHIPMODE,StringType,true), StructField(L_COMMENT,StringType,true))
scala> val dataRowRdd = dataRdd.map(p => Row(p(0).toLong, p(1).toLong, p(2).toLong, p(3).toInt, p(4).toDouble, p(5).toDouble, p(6).toDouble, p(7).toDouble, p(8), p(9), p(10), p(11), p(12), p(13), p(14), p(15)))
dataRowRdd: org.apache.spark.rdd.RDD[org.apache.spark.sql.Row] = MapPartitionsRDD[3] at map at <console>:30
scala> val dataFrame = sqlContext.createDataFrame(dataRowRdd, schema)
dataFrame: org.apache.spark.sql.DataFrame = [L_ORDERKEY: bigint, L_PARTKEY: bigint ... 14 more fields]
scala> dataFrame.createOrReplaceTempView("lineitem")
scala> spark.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from lineitem where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show()
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+
|l_returnflag|l_linestatus|    sum_qty|      sum_base_price|      sum_disc_price|          sum_charge|           avg_qty|         avg_price|           avg_disc|count_order|
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+
|           N|           O|7.5697385E7|1.135107538838699...|1.078345555027154...|1.121504616321447...|25.501957856643052|38241.036487881756|0.04999335309103123|    2968297|
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+
scala> sqlContext.sql("CREATE TEMPORARY VIEW item USING com.aliyun.oss " +
     |   "OPTIONS (" +
     |   "oss.bucket 'select-test-sz', " +
     |   "oss.prefix 'data', " +
     |   "oss.schema 'L_ORDERKEY long, L_PARTKEY long, L_SUPPKEY long, L_LINENUMBER int, L_QUANTITY double, L_EXTENDEDPRICE double, L_DISCOUNT double, L_TAX double, L_RETURNFLAG string, L_LINESTATUS string, L_SHIPDATE string, L_COMMITDATE string, L_RECEIPTDATE string, L_SHIPINSTRUCT string, L_SHIPMODE string, L_COMMENT string'," +
     |   "oss.data.format 'csv'," + // we only support csv now
     |   "oss.input.csv.header 'None'," +
     |   "oss.input.csv.recordDelimiter '\n'," +
     |   "oss.input.csv.fieldDelimiter '|'," +
     |   "oss.input.csv.commentChar '#'," +
     |   "oss.input.csv.quoteChar '\"'," +
     |   "oss.output.csv.recordDelimiter '\n'," +
     |   "oss.output.csv.fieldDelimiter ','," +
     |   "oss.output.csv.commentChar '#'," +
     |   "oss.output.csv.quoteChar '\"'," +
     |   "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " +
     |   "oss.accessKeyId 'Your Access Key Id', " +
     |   "oss.accessKeySecret 'Your Access Key Secret')")
res2: org.apache.spark.sql.DataFrame = []
scala> sqlContext.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from item where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show()
scala> sqlContext.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from item where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show()
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+
|l_returnflag|l_linestatus|    sum_qty|      sum_base_price|      sum_disc_price|          sum_charge|           avg_qty|        avg_price|           avg_disc|count_order|
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+
|           N|           O|7.5697385E7|1.135107538838701E11|1.078345555027154...|1.121504616321447...|25.501957856643052|38241.03648788181|0.04999335309103024|    2968297|
+------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+

    The comparison shows a significant performance gain: the query with OSS Select finished in 38 seconds, while the standard Spark SQL query took 2.5 minutes. The Spark Jobs page in the Spark Web UI displays the execution metrics for two completed jobs: Job 0 (the query using only Spark SQL, corresponding to show at <console>:26) took 2.5 minutes and consisted of 2 stages and 237 tasks. Job 1 (the query using OSS Select, corresponding to show at <console>:28) took 38 seconds and consisted of 2 stages and 239 tasks. All stages and tasks completed successfully, demonstrating a substantial reduction in query time when using OSS Select.

    References