Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/11557#discussion_r55186195
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/ng/ParseDriver.scala
---
@@ -0,0 +1,205 @@
+/*
+ * 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.catalyst.parser.ng
+
+import org.antlr.v4.runtime._
+import org.antlr.v4.runtime.atn.PredictionMode
+import org.antlr.v4.runtime.misc.ParseCancellationException
+
+import org.apache.spark.Logging
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.TableIdentifier
+import org.apache.spark.sql.catalyst.expressions.Expression
+import org.apache.spark.sql.catalyst.parser.ParserInterface
+import org.apache.spark.sql.catalyst.parser.ng.SqlBaseParser._
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
+import org.apache.spark.util.Utils
+
+/**
+ * Base SQL parsing infrastructure.
+ */
+abstract class AbstractSqlParser extends ParserInterface with Logging {
+
+ /** Creates Expression for a given SQL string. */
+ override def parseExpression(sqlText: String): Expression =
parse(sqlText) { parser =>
+ astBuilder.visitSingleExpression(parser.singleExpression())
+ }
+
+ /** Creates TableIdentifier for a given SQL string. */
+ override def parseTableIdentifier(sqlText: String): TableIdentifier =
parse(sqlText) { parser =>
+ astBuilder.visitSingleTableIdentifier(parser.singleTableIdentifier())
+ }
+
+ /** Creates LogicalPlan for a given SQL string. */
+ override def parsePlan(sqlText: String): LogicalPlan = parse(sqlText) {
parser =>
+ astBuilder.visitSingleStatement(parser.singleStatement()) match {
+ case plan: LogicalPlan => plan
+ case _ => nativeCommand(sqlText)
+ }
+ }
+
+ /** Get the builder (visitor) which converts a ParseTree into a AST. */
+ protected def astBuilder: AstBuilder
+
+ /** Create a native command, or fail when this is not supported. */
+ protected def nativeCommand(sqlText: String): LogicalPlan = {
+ throw new AnalysisException(s"Unsupported SQL statement:\n$sqlText")
+ }
+
+ protected def parse[T](command: String)(toResult: SqlBaseParser => T): T
= {
+ logInfo(s"Parsing command: $command")
+
+ val lexer = new SqlBaseLexer(new ANTLRNoCaseStringStream(command))
+ lexer.removeErrorListeners()
+ lexer.addErrorListener(ParseErrorListener)
+
+ val tokenStream = new CommonTokenStream(lexer)
+ val parser = new SqlBaseParser(tokenStream)
+ parser.addParseListener(PostProcessor)
+ parser.removeErrorListeners()
+ parser.addErrorListener(ParseErrorListener)
+
+ try {
+ try {
+ // first, try parsing with potentially faster SLL mode
+ parser.getInterpreter.setPredictionMode(PredictionMode.SLL)
+ toResult(parser)
+ }
+ catch {
+ case e: ParseCancellationException =>
+ // if we fail, parse with LL mode
+ tokenStream.reset() // rewind input stream
+ parser.reset()
+
+ // Try Again.
+ parser.getInterpreter.setPredictionMode(PredictionMode.LL)
+ toResult(parser)
+ }
+ }
+ catch {
+ case e: AnalysisException =>
+ (e.line, e.startPosition) match {
+ case (Some(line), Some(position)) =>
--- End diff --
This still a WIP. It shows users what went wrong.
I want to move this into a separate exception.
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