cloud-fan commented on a change in pull request #26182: [SPARK-29523][SQL] SHOW
COLUMNS should do multi-catalog resolution.
URL: https://github.com/apache/spark/pull/26182#discussion_r340436799
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
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@@ -2912,6 +2912,32 @@ class AstBuilder(conf: SQLConf) extends
SqlBaseBaseVisitor[AnyRef] with Logging
RefreshTableStatement(visitMultipartIdentifier(ctx.multipartIdentifier()))
}
+ /**
+ * A command for users to list the column names for a table.
+ * This function creates a [[ShowColumnsStatement]] logical plan.
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * SHOW COLUMNS (FROM | IN) tableName=multipartIdentifier
+ * ((FROM | IN) namespace=multipartIdentifier)?
+ * }}}
+ */
+ override def visitShowColumns(ctx: ShowColumnsContext): LogicalPlan =
withOrigin(ctx) {
+ import org.apache.spark.sql.connector.catalog.CatalogV2Implicits._
+
+ val table = visitMultipartIdentifier(ctx.table)
+ val namespace = Option(ctx.namespace).map(visitMultipartIdentifier)
+ if (namespace.isDefined && namespace.get.length > 1) {
+ throw new ParseException(
+ s"Namespace name should have only one part if specified:
${namespace.get.quoted}", ctx)
+ }
+ if (table.length > 2) {
+ throw new ParseException(
+ s"Table name should have at most two parts: ${table.quoted}", ctx)
+ }
Review comment:
This is a tricky problem. Ideally, we should have a check at the parser
that: if namespace is specified, then table name should be a single part.
Unfortunately we support `SHOW COLUMNS FROM db1.t1 IN db1`. To keep
supporting it, we can't check anything in the parser. In the analyzer, we can
add a check before converting to the v1 command: if namespace is specified, it
must be a single part, and the table name must have <= 2 parts.
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