Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/14116#discussion_r70172079
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/systemcatalog/InformationSchema.scala
---
@@ -0,0 +1,230 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.spark.sql.execution.systemcatalog
+
+import scala.collection.mutable.ArrayBuffer
+
+import org.apache.spark.internal.Logging
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql._
+import org.apache.spark.sql.catalyst.catalog.CatalogDatabase
+import org.apache.spark.sql.catalyst.dsl.plans._
+import org.apache.spark.sql.catalyst.expressions.Alias
+import org.apache.spark.sql.catalyst.plans.logical.Project
+import org.apache.spark.sql.execution.datasources._
+import org.apache.spark.sql.sources._
+import org.apache.spark.sql.types._
+
+object InformationSchema extends Logging {
+ def register(sparkSession: SparkSession, relation: BaseRelation, names:
Seq[String]) {
+ val plan = LogicalRelation(relation).analyze
+ val projectList = plan.output.zip(plan.schema).map {
+ case (attr, col) => Alias(attr, col.name)()
+ }
+ sparkSession.sessionState.executePlan(Project(projectList, plan))
+ for (name <- names)
+ sparkSession.sessionState.catalog.createTempView(name, plan,
overrideIfExists = true)
+ }
+
+ def build(sparkSession: SparkSession) {
+ // Create database
+ val informationSchemaDb = new CatalogDatabase(
+ "information_schema",
+ "Spark information schema",
+ locationUri = "/tmp/",
+ Map())
+ sparkSession.sessionState.catalog.createDatabase(informationSchemaDb,
ignoreIfExists = true)
+
+ // Create tables
+ register(sparkSession, new DatabasesRelation(sparkSession),
Seq("schemata", "databases"))
+ register(sparkSession, new TablesRelation(sparkSession), Seq("tables"))
+ register(sparkSession, new ViewsRelation(sparkSession), Seq("views"))
+ register(sparkSession, new ColumnsRelation(sparkSession),
Seq("columns"))
+ register(sparkSession, new SessionVariablesRelation(sparkSession),
Seq("session_variables"))
+ }
+}
+
+class DatabasesSource extends SchemaRelationProvider {
+ override def createRelation(
+ sqlContext: SQLContext,
+ parameters: Map[String, String],
+ schema: StructType): BaseRelation = {
+ DatabasesRelation(sqlContext.sparkSession)
+ }
+}
+
+case class DatabasesRelation(@transient sparkSession: SparkSession)
+ extends BaseRelation with PrunedFilteredScan {
+
+ override def sqlContext: SQLContext = sparkSession.sqlContext
+
+ override def schema: StructType = StructType(Seq(
+ StructField("CATALOG_NAME", StringType, false),
+ StructField("SCHEMA_NAME", StringType, false)
+ ))
+
+ override def buildScan(requiredColumns: Array[String], filters:
Array[Filter]): RDD[Row] = {
+ sparkSession.catalog.listDatabases()
--- End diff --
I was thinking having sparksession.catalog calling these commands, but I
guess it is ok this way too ...
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