twalthr commented on code in PR #23365:
URL: https://github.com/apache/flink/pull/23365#discussion_r1316945655
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flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/api/config/TableConfigOptions.java:
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@@ -313,4 +325,32 @@ public InlineElement getDescription() {
return description;
}
}
+
+ /** Strategy to expand columns in {@code SELECT *} queries. */
+ @PublicEvolving
+ public enum ColumnExpansionStrategy implements DescribedEnum {
+ EXCLUDE_ALIASED_VIRTUAL_METADATA_COLUMNS(
+ text(
+ "Excludes virtual metadata columns that reference a
metadata key via an alias. "
+ + "For example, a column declared as 'c
METADATA VIRTUAL FROM k' "
+ + "is not selected by default if the strategy
is applied.")),
+
+ EXCLUDE_DEFAULT_VIRTUAL_METADATA_COLUMNS(
+ text(
+ "Excludes virtual metadata columns that directly
reference a metadata key. "
+ + "For example, a column declared as 'k
METADATA VIRTUAL' "
+ + "is not selected by default if the strategy
is applied."));
Review Comment:
This is to provide more flexibility. E.g. if a metadata virtual column
should serve as a kind of system column, it might make sense to only set
`EXCLUDE_DEFAULT_VIRTUAL_METADATA_COLUMNS` and give users the chance to define
virtual metadata columns that are not excluded using the `METADATA FROM`
clause. Anyway I wanted to give some options already. I was also thinking about
supporting exclusions of computed columns in the first version, but this was
actually not part of the FLIP.
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