Can't fulltext search against reference column of vector

[komainu8]

Fix mroonga/mroonga#674.

What happend?

Groonga always returns that the number of hits is 0 when we execute full-text search against reference column of vector as below. Note that a lexicon (tags in this case) must have a tokenizer.

table_create bugs TABLE_PAT_KEY UInt32

table_create tags TABLE_PAT_KEY ShortText --default_tokenizer TokenDelimit
column_create tags name COLUMN_SCALAR ShortText

column_create bugs tags COLUMN_VECTOR tags

load --table bugs
[
["_key", "tags"],
[1, "Linux MySQL"],
[2, "MySQL Groonga"],
[3, "Mroonga"]
]

column_create tags bugs_tags_index COLUMN_INDEX bugs tags

select --table bugs --filter 'tags @ "MySQL"'
[[0,0.0,0.0],[[[0],[["_id","UInt32"],["_key","UInt32"],["tags","tags"]]]]]

Solution

In this PR, If the source of index was reference column, Groonga get key_type from a table that the reference column refer.

This problem occurs from 535844b.
If the source of index was reference column, Groonga couldn't get key and key_type correctly in the above modification.