feat(query): new table function infer_schema.

[youngsofun]

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Summary

Closes #9908

currently only support named stage, with parquet format.

examples:

mysql> select * from infer_schema(location=> '@s2/data/tuple.parquet');
+-------------+---------------------+----------+----------+
| column_name | type                | nullable | order_id |
+-------------+---------------------+----------+----------+
| id          | INT                 |        0 |        0 |
| t           | (A INT32, B STRING) |        0 |        1 |
+-------------+---------------------+----------+----------+

also support parameter pattern

select * from infer_schema(location => '@s2/data/', pattern => '.*parquet');

diff with desc <table>

• it is table function
• no Default and Extra; add order_id column
• as a table function, it's results is for processing, so nullable/ order_id column has type bool/uint64; while in desc <table>, all column is string

diff with copy/ select from stage

1. currently, arg value of table function must be const literal. so '@s2/data/' in the example is single quoted (as a string).
2. we currently only support infer the first file, so parameter files in not needed.

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Name	Status	Preview	Comments	Updated
databend	⬜️ Ignored (Inspect)			Feb 9, 2023 at 3:31AM (UTC)