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When use map function, the query plan change, query take much more cost

I create a map manully and want to use this map to finish some augument convert, yes the augument can convert, but the query plan changed, the query take much more cost: select count(*) from AA where "WID" = 2020092 select count(*) from AA where "WID" = map(20190701, 'map_test') my map map_test (20190701 = 2020092) The first query run much faster and it pass to the source oracle DB query is: select count(*) from oracle_DB.table where WID = 2020092, and pass just 1 item of result to denodo The second query pass below query to source oralce DB: SELECT t0.colA FROM oracle_DB.table t0 WHERE WID = 2020092, and it pass many items to denodo, let the denodo to do the count(*) function. My question is why? And how can delegate that count(*) to soruce oracle DB?
25-09-2019 11:26:55 -0400

2 Answers

I guess this is an enhancement which Denodo can do in the future? I encountered the same problem. Could Denodo team help on this topic? Thanks.
25-09-2019 23:18:27 -0400
Hi, I was able to reproduce the same behaviour in my environment. From the Execution Trace of the Query Results, I am able to identify the reason that the delegation isn't performed. Under the '**No delegation cause**', it is stated that '*The function 'map' cannot be delegated to this database*'. If you have a active support account with Denodo, I would recommend to raise a case in the Support Site to identify if can be added as an enhancement to Denodo Platform. Hope this helps!
Denodo Team
26-09-2019 01:26:13 -0400
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