Another block of ideas for 5.0. Related to expressions and queries...
0. Terse and consistent Expression API. 90% of expressions are done with
Properties now, but the remaining 10% are clunky and inconsistent. I am
thinking the main class (interface) should be called "Exp", combining static
methods from ExpressionFactory and common instance methods from Expression. The
API itself needs to be reworked for fluency and readability (e.g. no "Exp"
suffix in methods like "andExp()", etc.), and should be aligned with the more
modern Property API (e.g. "eq" instead of "matchExp").
1. Merge EJBQLQuery into ObjectSelect. I think we already have the machinery to
implement all features of EJBQLQuery (such as subqueries, EXISTS, etc.) in
ObjectSelect. So let's do that, and then create a parser (based on the old
EJBQL parser, but more Cayenne-centric) to parse ObjectSelects from Strings.
Remove EJBQLQuery, and all the ugliness needed to support its execution.
2. SelectById query is redundant. It can be deprecated and replaced with a
special expression applied to ObjectSelect. With the new Exp API this may look
like this:
ObjectSelect.query(MyEntity.class).where(Exp.byId(5));
On top of that we can probably do something via generated Properties.
3. SQLTemplate should be deprecated. SQLExec (and partially - SQLSelect)
replaces it. One feature that SQLTemplate supported is multiple sets of
PreparedStatement parameters ("batches"), that we can potentially port to
SQLExec.
4. Replace QueryResponse with QueryResult. Same thing, better API. Keeping them
both is redundant.
5. "statementFetchSize" should be fully integrated. Currently it has no effect
on MySQL, without somehow manually setting a few extra Statement parameters [1]
:
conn.createStatement(ResultSet.TYPE_FORWARD_ONLY,
ResultSet.CONCUR_READ_ONLY);
Cayenne should take care of it, allowing the users to process large cursors [2].
6. "timeout(long,TimeUnit)" - should result in setting Statement timeout. Need
to test how well it works on different DBs.
Andrus
[1]
https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-implementation-notes.html
<https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-implementation-notes.html>
[2] https://github.com/nhl/link-move/issues/142
