Hi, Jingsong,
Thank you very much for your suggestion.
I verified that use `tEnv.sqlUpdate("xxx")` and `tEnv.explain(false)` to do
validation, it works.
But this method needs the connector jar, which is very inconvenient to use.
Hi, Danny,
Many thanks for providing very useful explanations.
The user case is users will register some source/sink tables, udf to
catalog service first, and then they will write and modify SQL like "insert
into sinkTable select * from sourceTable where a>1" on Web SQLEditor. The
platform wants to tell the user whether the SQL is valid includes the
detailed position if an error occurs.
For the `insert target table`, the platform wants to validate the table
exists, field name and field type.
Best,
Kaibo
Danny Chan <yuzhao....@gmail.com> 于2019年12月30日周一 下午5:37写道：
> Hi, Kaibo Zhou ~
>
> There are several phrases that a SQL text get to execution graph what can
> be run with Flink runtime:
>
>
> 1. Sql Parse: parse the sql text to AST(sql node tree)
> 2. Sql node(row type) validation, this includes the tables/schema inference
> 3. Sql-to-rel conversion, convert the sql node to RelNode(relational
> algebra)
> 4. Promote the relational expression with planner(Volcano or Hep) then
> converts to execution convention nodes
> 5. Genegate the code and the execution graph
>
> For the first 3 steps, Apache Flink uses the Apache Calcite as the
> implementation, that means a SQL test passed to table environment would
> always have a SQL parse/validation/sql-to-rel conversion.
>
> For example, a code snippet like tableEnv.sqlQuery("INSERT INTO sinkTable
> SELECT f1,f2 FROM sourceTable”), the query part “SELECT f1,f2 FROM
> sourceTable” was validated.
>
> But you are right, for Flink SQL, an insert statement target table is not
> validated during the validation phrase, actually we validate the “select”
> clause first, extract the target table identifier and we validate the
> schema of “select” clause and target table are the same when we invoke
> write to sink(after step 4).
>
>
> For most of the cases this is okey, can you share your cases ? What kind
> of validation do you want for the insert target table ?
>
> We are planning to include the insert target table validation in the step2
> for 2 reasons:
>
> • The computed column validation(stored or virtual)
> • The insert implicit type coercion
>
> But this would comes for Flink version 1.11 ~
>
>
> Best,
> Danny Chan
> 在 2019年12月27日 +0800 PM5:44，dev@flink.apache.org，写道：
> >
> > "INSERT INTO
> > sinkTable SELECT f1,f2 FROM sourceTable"
>
