Passing down partial predicates to translator

[mickalas]

Hi,

I am implementing a translator that I will be using within an embedded teiid instance.

Considering the method in ExecutionFactory

public ResultSetExecution createResultSetExecution(QueryExpression command, ExecutionContext executionContext, RuntimeMetadata metadata, TradeRecConnection connection) throws TranslatorException;

What would be really good for me is for teiid to do pretty much all the SQL handling so that I just provide the raw data. This is easy to achieve by using the supports methods.

But I can handle and optimise predicates on a few of the columns, so it would be good if I could specify these columns and have the predicates that can be applied to them passed down.

Alternatively if I could get a handle on the original query, ideally in a parse tree, I could do this myself. Is there any way to do this?

Just so I am clear.

Given a query:

SELECT a,b,c FROM table WHERE a = 'x' AND b = 'y'

and assuming I can handle predicates involving column a.

Then in the case above I'd like to be passed

SELECT a,b,c FROM table WHERE a = 'x'

And for teiid to apply the predicate on column b.

Alteratively teiid could pass

SELECT a,b,c FROM table

but I would be able to get hold of the original query and apply the predicates on the column myself so that all rows returned only contained

column a values of 'x'. Teiid would apply the predicates itself, reapplying the predicate to a.

I am using 8.7. It may be that you can do this - but looking at the API I cannot see how at the moment.

Any help appreciated.

Mick

[rareddy]

Mick,

Yes, you can do such processing. How are you building your metadata for your source? When you are creating the schema for "table" you need to set property called "searchability" to false on column "b" and by default it is true. Take look at at "Column.setSearchType" method. When column is seachable, Teiid query engine passes any predicates involved with it, otherwise engine will handle it.

An example see here https://github.com/teiid/teiid/blob/master/connectors/translator-solr/src/main/java/org/teiid/translator/solr/SolrMetadataProcessor.java

HTH.

Ramesh..

[shawkins]

> Then in the case above I'd like to be passed

> SELECT a,b,c FROM table WHERE a = 'x'

If column b is marked as unsearchable (DDL Metadata - Teiid 8.9 (draft) - Project Documentation Editor), but is a comparable type, then we'll not push the b predicate and just evaluate it in the engine.

> Alteratively teiid could pass

> SELECT a,b,c FROM table

Here you are asking for the translator to optional apply predicates and also apply them in the engine.  In this case, no there is not anything for that.  The strategy is also a little awkward for anything other than a simple query with conjunctive predicates.  An optional join predicate, OR, etc. would not be as easy to handle this way.

[mickalas]

Just tried that out and it works a treat.

Thanks a lot for both your help.

Mick