Hi community, Temporal table join in Flink is a powerful feature, especially processing time temporal table join, which is very commonly used in production. However, the syntax of temporal table join only supports 'FOR SYSTEM_TIME AS OF' left table's time attribute field currently. e.g.,
``` SELECT * FROM Orders AS o JOIN Products FOR SYSTEM_TIME AS OF o.proctime AS p ON o.productId = p.productId ``` That means the users have to explicitly define a the proctime field either in the left table DDL or the left temporary view, which is inconvenient to use. >> Preferred solution I think maybe we can add a pseudo-column `PROCTIME` (or `_PROCTIME` to avoid conflict) to the table by default, just like the pseudo-column of classic database, e.g., `ROWID` in Oracle. In this way, we can use Temporal table join very conveniently. >> Less elegant solution Actually, we have another simpler solution, i.e., enrich the syntax for temporal table join to support 'FOR SYSTEM_TIME AS OF PROCTIME()'. It is also very convenient, However, the `PROCTIME()` in 'FOR SYSTEM_TIME AS OF PROCTIME()' is ambiguous, because it cannot tell where the version time of temporal table comes from, left table or right table? The former is what we want. So I think this solution is not preferred. Looking forward to your feedback~ Best, Shuo
