fhueske commented on code in PR #28396:
URL: https://github.com/apache/flink/pull/28396#discussion_r3429467999
##########
flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java:
##########
@@ -908,6 +910,45 @@ ANY, and(logical(LogicalTypeRoot.BOOLEAN), LITERAL)
"org.apache.flink.table.runtime.functions.ptf.FromChangelogFunction")
.build();
+ /**
+ * Built-in proxy function for the LATERAL SNAPSHOT temporal join.
+ *
+ * <p>The function itself has no runtime — it is a planner placeholder. A
dedicated optimizer
+ * rule recognizes calls of this function inside a {@code LATERAL} context
and rewrites the
+ * surrounding correlate/join into a specialized stream operator that
joins probe-side records
+ * against an updating temporal build-side table.
+ */
+ public static final BuiltInFunctionDefinition SNAPSHOT =
+ BuiltInFunctionDefinition.newBuilder()
+ .name("SNAPSHOT")
+ .kind(PROCESS_TABLE)
+ .staticArguments(
+ StaticArgument.table(
+ "input",
+ Row.class,
+ false,
+ EnumSet.of(
+ StaticArgumentTrait.TABLE,
+
StaticArgumentTrait.ROW_SEMANTIC_TABLE,
+
StaticArgumentTrait.SUPPORT_UPDATES,
+
StaticArgumentTrait.REQUIRE_UPDATE_BEFORE,
+
StaticArgumentTrait.REQUIRE_FULL_DELETE)),
+ StaticArgument.scalar(
+ "load_completed_condition",
DataTypes.STRING(), true),
+ StaticArgument.scalar(
+ "load_completed_time",
DataTypes.TIMESTAMP(3), true),
+ StaticArgument.scalar(
+ "load_completed_idle_timeout",
+ DataTypes.INTERVAL(DataTypes.SECOND()),
+ true),
+ StaticArgument.scalar(
Review Comment:
We can't add this check yet because `StreamPhysicalProcessTableFunction`
will throw if `disableSystemArguments(true)` is set.
So we have to wait until we've added a rule that prevents
`StreamPhysicalProcessTableFunction` to be created for `SNAPSHOT`.
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