size of frq record is very huge in the table [LUCENE-5742]

Hi,
We are trying the use the lucene with jdbcstore, In production, the
'frq' and 'tis' record size had grown too huge,
We are unable to resize the these records to smaller size eventhough we try to call reindex and optimize using different mergeFactor and maxMergeDocs

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Migrated from [LUCENE-5742](https://issues.apache.org/jira/browse/LUCENE-5742) by Maheshwara Reddy
Environment:
```
Linux, Jboss, Oracle database
```

Start by reviewing the JDBCStore behavior involved in the frq and tis records, using the reported Linux, JBoss, and Oracle environment as a reproduction context. Check what reindex and optimize do with different mergeFactor and maxMergeDocs settings, and document whether those records can be reduced to a smaller size.

Written by the indexing model from the issue text.