comment address

Author: xuanyuanking

docs/sql-keywords.md

@@ -19,12 +19,13 @@ license: |
   limitations under the License.
 ---
 
-When `spark.sql.dialect.spark.ansi.enabled` is true, Spark SQL has two kinds of keywords:
+When `spark.sql.dialect=PostgreSQL` or keep default `spark.sql.dialect=Spark` with setting `spark.sql.dialect.spark.ansi.enabled` to true, Spark SQL will use the ANSI mode parser.
+In this mode, Spark SQL has two kinds of keywords:
 * Reserved keywords: Keywords that are reserved and can't be used as identifiers for table, view, column, function, alias, etc.
 * Non-reserved keywords: Keywords that have a special meaning only in particular contexts and can be used as identifiers in other contexts. For example, `SELECT 1 WEEK` is an interval literal, but WEEK can be used as identifiers in other places.
 
-When `spark.sql.dialect.spark.ansi.enabled` is false, Spark SQL has two kinds of keywords:
-* Non-reserved keywords: Same definition as the one when `spark.sql.dialect.spark.ansi.enabled=true`.
+When the ANSI mode is disabled, Spark SQL has two kinds of keywords:
+* Non-reserved keywords: Same definition as the one when the ANSI mode enabled.
 * Strict-non-reserved keywords: A strict version of non-reserved keywords, which can not be used as table alias.
 
 By default `spark.sql.dialect.spark.ansi.enabled` is false.

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -957,8 +957,7 @@ number
     | MINUS? BIGDECIMAL_LITERAL       #bigDecimalLiteral
     ;
 
-// When we use PostgreSQL dialect or use Spark dialect with
-// `spark.sql.dialect.spark.ansi.enabled=true`, there are 2 kinds of keywords in Spark SQL.
+// When `use_SQL_standard_keywords=true`, there are 2 kinds of keywords in Spark SQL.
 // - Reserved keywords:
 //     Keywords that are reserved and can't be used as identifiers for table, view, column,
 //     function, alias, etc.
@@ -1158,10 +1157,9 @@ ansiNonReserved
     | YEARS
     ;
 
-// When we use Spark dialect with `spark.sql.dialect.spark.ansi.enabled=false`,
-// there are 2 kinds of keywords in Spark SQL.
+// When `use_SQL_standard_keywords=false`, there are 2 kinds of keywords in Spark SQL.
 // - Non-reserved keywords:
-//     Same definition as the one when the ANSI mode enabled.
+//     Same definition as the one when `use_SQL_standard_keywords=true`.
 // - Strict-non-reserved keywords:
 //     A strict version of non-reserved keywords, which can not be used as table alias.
 // You can find the full keywords list by searching "Start of the keywords list" in this file.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/ParseDriver.scala

@@ -89,7 +89,9 @@ abstract class AbstractSqlParser(conf: SQLConf) extends ParserInterface with Log
   protected def parse[T](command: String)(toResult: SqlBaseParser => T): T = {
     logDebug(s"Parsing command: $command")
 
-    val useSQLStandardKeywords = Dialect.withName(conf.dialect) match {
+    // When we use PostgreSQL dialect or use Spark dialect with setting
+    // `spark.sql.dialect.spark.ansi.enabled=true`, the parser will use ANSI SQL standard keywords.
+    val useSQLStandardKeywords = conf.dialect match {
       case Dialect.POSTGRESQL => true
       case Dialect.SPARK => conf.dialectSparkAnsiEnabled
     }

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -2515,9 +2515,9 @@ class SQLConf extends Serializable with Logging {
 
   def intervalOutputStyle: IntervalStyle.Value = IntervalStyle.withName(getConf(INTERVAL_STYLE))
 
-  def dialect: String = getConf(DIALECT)
+  def dialect: Dialect.Value = Dialect.withName(getConf(DIALECT))
 
-  def usePostgreSQLDialect: Boolean = dialect == Dialect.POSTGRESQL.toString
+  def usePostgreSQLDialect: Boolean = dialect == Dialect.POSTGRESQL
 
   def dialectSparkAnsiEnabled: Boolean = getConf(DIALECT_SPARK_ANSI_ENABLED)