[Cdash] client_job table size and performance issues

[Nils Gladitz]

With CDash 8185a80c32e8dc58c69237aa950b47bfa0b86084 and PostgreSQL I've 
got some performance issues:
   http://www.cmake.org/Bug/view.php?id=15473

I manually added an index which alleviated the original issue but 
related queries are also/still slow:

CEST LOG:  duration: 57772.638 ms  execute pdo_stmt_000000ae: SELECT id 
FROM client_job WHERE scheduleid=90 ORDER BY id DESC LIMIT 1

My client_job table has 1215091 rows (363 MB).

Is it meant to grow this large? Are there any configuration options that 
might influence its size?

Nils