lincoln-lil commented on a change in pull request #9335: [FLINK-13503][API] Add
contract in `LookupableTableSource` to specify the behavior when lookupKeys
contains null.
URL: https://github.com/apache/flink/pull/9335#discussion_r310066219
##########
File path:
flink-table/flink-table-common/src/main/java/org/apache/flink/table/sources/LookupableTableSource.java
##########
@@ -34,12 +34,29 @@
/**
* Gets the {@link TableFunction} which supports lookup one key at a
time.
+ *
* @param lookupKeys the chosen field names as lookup keys, it is in
the defined order
+ *
+ * <p>IMPORTANT:
+ * If the returned {@link TableFunction} receives a lookup request with
null value in lookup keys, expect
Review comment:
Give more detailed comments here maybe more clearly for understanding,
1. lookupKeys are nullable
2. should carefully deal with `null` value lookup in each concrete store
engine, e.g., in MySQL this can a `is null` query
...
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