Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/14116#discussion_r70327875
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/systemcatalog/InformationSchema.scala
---
@@ -0,0 +1,336 @@
+/*
+ * 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 java.sql.{Date, Timestamp}
+
+import scala.collection.mutable.ArrayBuffer
+
+import org.apache.commons.lang3.StringUtils
+
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql._
+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._
+
+/**
+ * INFORMATION_SCHEMA is a database consisting views which provide
information about all of the
+ * tables, views, columns in a database.
+ */
+object InformationSchema {
+ val INFORMATION_SCHEMA = "information_schema"
+ /**
+ * Register INFORMATION_SCHEMA database.
+ */
+ def registerInformationSchema(sparkSession: SparkSession): Unit = {
+ sparkSession.sql(s"CREATE DATABASE IF NOT EXISTS $INFORMATION_SCHEMA")
+ registerView(sparkSession, new DatabasesRelationProvider,
Seq("schemata", "databases"))
+ registerView(sparkSession, new TablesRelationProvider, Seq("tables"))
+ registerView(sparkSession, new ViewsRelationProvider, Seq("views"))
+ registerView(sparkSession, new ColumnsRelationProvider, Seq("columns"))
+ registerView(sparkSession, new SessionVariablesRelationProvider,
Seq("session_variables"))
+ }
+
+ /**
+ * Register a INFORMATION_SCHEMA relation provider as a temporary view
of Spark Catalog.
+ */
+ private def registerView(
+ sparkSession: SparkSession,
+ relationProvider: SchemaRelationProvider,
+ names: Seq[String]) {
+ val plan =
+
LogicalRelation(relationProvider.createRelation(sparkSession.sqlContext, null,
null)).analyze
+ val projectList = plan.output.zip(plan.schema).map {
+ case (attr, col) => Alias(attr, col.name)()
+ }
+ sparkSession.sessionState.executePlan(Project(projectList, plan))
+ for (name <- names) {
+ // TODO(dongjoon): This is a hack to give a database concept for
Spark temporary views.
+ // We should generalize this later.
+
sparkSession.sessionState.catalog.createTempView(s"$INFORMATION_SCHEMA.$name",
+ plan, overrideIfExists = true)
+ }
+ }
+
+ /**
+ * Compile filter array into single string condition.
+ */
+ private[systemcatalog] def getConditionExpressionString(filters:
Array[Filter]): String = {
+ val str = filters.flatMap(InformationSchema.compileFilter).map(p =>
s"($p)").mkString(" AND ")
+ if (str.length == 0) "TRUE" else str
+ }
+
+ /**
+ * Convert filter into string expression.
+ */
+ private[systemcatalog] def compileFilter(f: Filter): Option[String] = {
--- End diff --
Yep, right.
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