[SPARK-18572][SQL] Add a method `listPartitionNames` to `ExternalCatalog`

(Link to Jira issue: https://issues.apache.org/jira/browse/SPARK-18572)

## What changes were proposed in this pull request?

Currently Spark answers the `SHOW PARTITIONS` command by fetching all of the table's partition metadata from the external catalog and constructing partition names therefrom. The Hive client has a `getPartitionNames` method which is many times faster for this purpose, with the performance improvement scaling with the number of partitions in a table.

To test the performance impact of this PR, I ran the `SHOW PARTITIONS` command on two Hive tables with large numbers of partitions. One table has ~17,800 partitions, and the other has ~95,000 partitions. For the purposes of this PR, I'll call the former table `table1` and the latter table `table2`. I ran 5 trials for each table with before-and-after versions of this PR. The results are as follows:

Spark at bdc8153, `SHOW PARTITIONS table1`, times in seconds:
7.901
3.983
4.018
4.331
4.261

Spark at bdc8153, `SHOW PARTITIONS table2`
(Timed out after 10 minutes with a `SocketTimeoutException`.)

Spark at this PR, `SHOW PARTITIONS table1`, times in seconds:
3.801
0.449
0.395
0.348
0.336

Spark at this PR, `SHOW PARTITIONS table2`, times in seconds:
5.184
1.63
1.474
1.519
1.41

Taking the best times from each trial, we get a 12x performance improvement for a table with ~17,800 partitions and at least a 426x improvement for a table with ~95,000 partitions. More significantly, the latter command doesn't even complete with the current code in master.

This is actually a patch we've been using in-house at VideoAmp since Spark 1.1. It's made all the difference in the practical usability of our largest tables. Even with tables with about 1,000 partitions there's a performance improvement of about 2-3x.

## How was this patch tested?

I added a unit test to `VersionsSuite` which tests that the Hive client's `getPartitionNames` method returns the correct number of partitions.

Author: Michael Allman <michael@videoamp.com>

Closes #15998 from mallman/spark-18572-list_partition_names.

5 files changed, 125 insertions, 2 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalog.scala
index 259008f183..4b8cac8f32 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalog.scala
@@ -190,14 +190,36 @@ abstract class ExternalCatalog {
       spec: TablePartitionSpec): Option[CatalogTablePartition]
 
   /**
+   * List the names of all partitions that belong to the specified table, assuming it exists.
+   *
+   * For a table with partition columns p1, p2, p3, each partition name is formatted as
+   * `p1=v1/p2=v2/p3=v3`. Each partition column name and value is an escaped path name, and can be
+   * decoded with the `ExternalCatalogUtils.unescapePathName` method.
+   *
+   * The returned sequence is sorted as strings.
+   *
+   * A partial partition spec may optionally be provided to filter the partitions returned, as
+   * described in the `listPartitions` method.
+   *
+   * @param db database name
+   * @param table table name
+   * @param partialSpec partition spec
+   */
+  def listPartitionNames(
+      db: String,
+      table: String,
+      partialSpec: Option[TablePartitionSpec] = None): Seq[String]
+
+  /**
    * List the metadata of all partitions that belong to the specified table, assuming it exists.
    *
    * A partial partition spec may optionally be provided to filter the partitions returned.
    * For instance, if there exist partitions (a='1', b='2'), (a='1', b='3') and (a='2', b='4'),
    * then a partial spec of (a='1') will return the first two only.
+   *
    * @param db database name
    * @param table table name
-   * @param partialSpec  partition spec
+   * @param partialSpec partition spec
    */
   def listPartitions(
       db: String,
@@ -210,7 +232,7 @@ abstract class ExternalCatalog {
    *
    * @param db database name
    * @param table table name
-   * @param predicates  partition-pruning predicates
+   * @param predicates partition-pruning predicates
    */
   def listPartitionsByFilter(
       db: String,
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
index 880a7a0dc4..a6bebe1a39 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
@@ -28,6 +28,7 @@ import org.apache.spark.{SparkConf, SparkException}
 import org.apache.spark.sql.AnalysisException
 import org.apache.spark.sql.catalyst.{FunctionIdentifier, TableIdentifier}
 import org.apache.spark.sql.catalyst.analysis._
+import org.apache.spark.sql.catalyst.catalog.ExternalCatalogUtils.escapePathName
 import org.apache.spark.sql.catalyst.expressions.Expression
 import org.apache.spark.sql.catalyst.util.StringUtils
 
@@ -488,6 +489,19 @@ class InMemoryCatalog(
     }
   }
 
+  override def listPartitionNames(
+      db: String,
+      table: String,
+      partialSpec: Option[TablePartitionSpec] = None): Seq[String] = synchronized {
+    val partitionColumnNames = getTable(db, table).partitionColumnNames
+
+    listPartitions(db, table, partialSpec).map { partition =>
+      partitionColumnNames.map { name =>
+        escapePathName(name) + "=" + escapePathName(partition.spec(name))
+      }.mkString("/")
+    }.sorted
+  }
+
   override def listPartitions(
       db: String,
       table: String,
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
index da3a2079f4..7a3d2097a8 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
@@ -749,6 +749,26 @@ class SessionCatalog(
   }
 
   /**
+   * List the names of all partitions that belong to the specified table, assuming it exists.
+   *
+   * A partial partition spec may optionally be provided to filter the partitions returned.
+   * For instance, if there exist partitions (a='1', b='2'), (a='1', b='3') and (a='2', b='4'),
+   * then a partial spec of (a='1') will return the first two only.
+   */
+  def listPartitionNames(
+      tableName: TableIdentifier,
+      partialSpec: Option[TablePartitionSpec] = None): Seq[String] = {
+    val db = formatDatabaseName(tableName.database.getOrElse(getCurrentDatabase))
+    val table = formatTableName(tableName.table)
+    requireDbExists(db)
+    requireTableExists(TableIdentifier(table, Option(db)))
+    partialSpec.foreach { spec =>
+      requirePartialMatchedPartitionSpec(Seq(spec), getTableMetadata(tableName))
+    }
+    externalCatalog.listPartitionNames(db, table, partialSpec)
+  }
+
+  /**
    * List the metadata of all partitions that belong to the specified table, assuming it exists.
    *
    * A partial partition spec may optionally be provided to filter the partitions returned.
@@ -762,6 +782,9 @@ class SessionCatalog(
     val table = formatTableName(tableName.table)
     requireDbExists(db)
     requireTableExists(TableIdentifier(table, Option(db)))
+    partialSpec.foreach { spec =>
+      requirePartialMatchedPartitionSpec(Seq(spec), getTableMetadata(tableName))
+    }
     externalCatalog.listPartitions(db, table, partialSpec)
   }
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalogSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalogSuite.scala
index 3b39f420af..00e663c324 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalogSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalogSuite.scala
@@ -346,6 +346,31 @@ abstract class ExternalCatalogSuite extends SparkFunSuite with BeforeAndAfterEac
     assert(new Path(partitionLocation) == defaultPartitionLocation)
   }
 
+  test("list partition names") {
+    val catalog = newBasicCatalog()
+    val newPart = CatalogTablePartition(Map("a" -> "1", "b" -> "%="), storageFormat)
+    catalog.createPartitions("db2", "tbl2", Seq(newPart), ignoreIfExists = false)
+
+    val partitionNames = catalog.listPartitionNames("db2", "tbl2")
+    assert(partitionNames == Seq("a=1/b=%25%3D", "a=1/b=2", "a=3/b=4"))
+  }
+
+  test("list partition names with partial partition spec") {
+    val catalog = newBasicCatalog()
+    val newPart = CatalogTablePartition(Map("a" -> "1", "b" -> "%="), storageFormat)
+    catalog.createPartitions("db2", "tbl2", Seq(newPart), ignoreIfExists = false)
+
+    val partitionNames1 = catalog.listPartitionNames("db2", "tbl2", Some(Map("a" -> "1")))
+    assert(partitionNames1 == Seq("a=1/b=%25%3D", "a=1/b=2"))
+
+    // Partial partition specs including "weird" partition values should use the unescaped values
+    val partitionNames2 = catalog.listPartitionNames("db2", "tbl2", Some(Map("b" -> "%=")))
+    assert(partitionNames2 == Seq("a=1/b=%25%3D"))
+
+    val partitionNames3 = catalog.listPartitionNames("db2", "tbl2", Some(Map("b" -> "%25%3D")))
+    assert(partitionNames3.isEmpty)
+  }
+
   test("list partitions with partial partition spec") {
     val catalog = newBasicCatalog()
     val parts = catalog.listPartitions("db2", "tbl2", Some(Map("a" -> "1")))
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalogSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalogSuite.scala
index f9c4b2687b..5cc772d8e9 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalogSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalogSuite.scala
@@ -878,6 +878,31 @@ class SessionCatalogSuite extends SparkFunSuite {
       "the partition spec (a, b) defined in table '`db2`.`tbl1`'"))
   }
 
+  test("list partition names") {
+    val catalog = new SessionCatalog(newBasicCatalog())
+    val expectedPartitionNames = Seq("a=1/b=2", "a=3/b=4")
+    assert(catalog.listPartitionNames(TableIdentifier("tbl2", Some("db2"))) ==
+      expectedPartitionNames)
+    // List partition names without explicitly specifying database
+    catalog.setCurrentDatabase("db2")
+    assert(catalog.listPartitionNames(TableIdentifier("tbl2")) == expectedPartitionNames)
+  }
+
+  test("list partition names with partial partition spec") {
+    val catalog = new SessionCatalog(newBasicCatalog())
+    assert(
+      catalog.listPartitionNames(TableIdentifier("tbl2", Some("db2")), Some(Map("a" -> "1"))) ==
+        Seq("a=1/b=2"))
+  }
+
+  test("list partition names with invalid partial partition spec") {
+    val catalog = new SessionCatalog(newBasicCatalog())
+    intercept[AnalysisException] {
+      catalog.listPartitionNames(TableIdentifier("tbl2", Some("db2")),
+        Some(Map("unknown" -> "unknown")))
+    }
+  }
+
   test("list partitions") {
     val catalog = new SessionCatalog(newBasicCatalog())
     assert(catalogPartitionsEqual(
@@ -887,6 +912,20 @@ class SessionCatalogSuite extends SparkFunSuite {
     assert(catalogPartitionsEqual(catalog.listPartitions(TableIdentifier("tbl2")), part1, part2))
   }
 
+  test("list partitions with partial partition spec") {
+    val catalog = new SessionCatalog(newBasicCatalog())
+    assert(catalogPartitionsEqual(
+      catalog.listPartitions(TableIdentifier("tbl2", Some("db2")), Some(Map("a" -> "1"))), part1))
+  }
+
+  test("list partitions with invalid partial partition spec") {
+    val catalog = new SessionCatalog(newBasicCatalog())
+    intercept[AnalysisException] {
+      catalog.listPartitions(
+        TableIdentifier("tbl2", Some("db2")), Some(Map("unknown" -> "unknown")))
+    }
+  }
+
   test("list partitions when database/table does not exist") {
     val catalog = new SessionCatalog(newBasicCatalog())
     intercept[NoSuchDatabaseException] {