wuchong commented on a change in pull request #9952: [FLINK-14321][sql-parser]
Support to parse watermark statement in SQL DDL
URL: https://github.com/apache/flink/pull/9952#discussion_r338424483
##########
File path:
flink-table/flink-sql-parser/src/main/codegen/includes/parserImpls.ftl
##########
@@ -27,9 +27,31 @@ void TableColumn(TableCreationContext context) :
UniqueKey(context.uniqueKeysList)
|
ComputedColumn(context)
+ |
+ Watermark(context)
)
}
+void Watermark(TableCreationContext context) :
+{
+ SqlIdentifier columnName;
+ SqlParserPos pos;
+ SqlNode watermarkStrategy;
+}
+{
+ <WATERMARK> {pos = getPos();} <FOR>
+ columnName = CompoundIdentifier()
+ <AS>
+ watermarkStrategy = Expression(ExprContext.ACCEPT_NON_QUERY) {
+ if (context.watermark != null) {
+ throw SqlUtil.newContextException(pos,
+ ParserResource.RESOURCE.multipleWatermarksUnsupported());
Review comment:
There is nothing to do with Expression syntax here. This is in order to give
a better exception message (with proper position) when multiple watermarks are
defined.
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