Timo Walther created FLINK-11890:
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Summary: Replace Table API string-based expressions by a Java DSL
Key: FLINK-11890
URL: https://issues.apache.org/jira/browse/FLINK-11890
Project: Flink
Issue Type: New Feature
Components: API / Table SQL
Reporter: Timo Walther
Assignee: Timo Walther
Currently, expressions in the Table API can be defined in two ways. Either via
the implicit Scala DSL or via custom strings:
{code}
Table revenue = orders
.filter("cCountry === 'FRANCE'")
.groupBy("cID, cName")
.select("cID, cName, revenue.sum AS revSum");
// vs.
val revenue = orders
.filter('cCountry === "FRANCE")
.groupBy('cID, 'cName)
.select('cID, 'cName, 'revenue.sum AS 'revSum)
{code}
The Java version of the Table API was always treated as a third class citizen.
In the past the string-based expression parser was/is:
- multiple times out of sync with the Scala DSL
- buggy because it was not properly tested
- it blows up the API as every method must accept both representations like
{{select(String)}} and {{select(Expression)}}
- confusing for users because it looks like SQL but is actually only SQL-like
- does not provide JavaDocs or further help in case of parse errors within the
IDE, a user can only consult the online documentation
We should discuss alternatives for the string-based expressions and might come
up with a DSL-like approach to make the Table API ready for the future.
This issue would be a big design shift for Table API users in Java. We need to
discuss if the benefits are worth the change. A first proof-of-concept/design
proposal will follow shortly.
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