Same SELECT with 3.0.2 uses different PLAN as 2.0.3 (and takes much loner)
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                 Key: CORE-5557
                 URL: http://tracker.firebirdsql.org/browse/CORE-5557
             Project: Firebird Core
          Issue Type: Bug
    Affects Versions: 3.0.2
            Reporter: Pósa József


Executing SELECT * FROM KIADT WHERE KIADF_SIF IN (SELECT SIF FROM TMPSYNC) 
command take 125 mses on 2.0.3 and 1 min 13 sec on 3.0.2.
The two databases are identical, with same data and indexes.

Firebird 2.0.3:

Plan
PLAN (TMPSYNC INDEX (RDB$PRIMARY94))
PLAN (KIADT NATURAL)

Adapted Plan
PLAN (TMPSYNC INDEX (INTEG_387))
PLAN (KIADT NATURAL)

------ Performance info ------
Prepare time = 15ms
Execute time = 125ms
Avg fetch time = 5,00 ms
Reads from disk to cache = 0
Writes from cache to disk = 0
Fetches from cache = 269 713

Firebird 3.0.2:

Plan
PLAN (TMPSYNC NATURAL)
PLAN (KIADT NATURAL)

------ Performance info ------
Prepare time = 15ms
Execute time = 1m 13s 828ms
Avg fetch time = 36 914,00 ms
Current memory = 1 189 906 648
Max memory = 1 218 517 920
Memory buffers = 50 000
Reads from disk to cache = 0
Writes from cache to disk = 0
Fetches from cache = 228 297 158


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