benj created DRILL-7747:
---------------------------
Summary: Function to determine Unknow fields / on fly generated
missing fields
Key: DRILL-7747
URL: https://issues.apache.org/jira/browse/DRILL-7747
Project: Apache Drill
Issue Type: Wish
Components: Functions - Drill
Affects Versions: 1.17.0
Reporter: benj
it would be really useful to have a function allowing to know if a field comes
from an existing column or not.
With this data:
{code:sql}
apache drill 1.17> SELECT * FROM dfs.test.`f1.parquet`;
+---+--------+-------+
| a | b | c |
+---+--------+-------+
| 1 | test-1 | other |
| 2 | test-2 | null |
| 3 | test-3 | old |
+---+--------+-------+
apache drill 1.17> SELECT * FROM dfs.test.`f2.parquet`;
+----+---------+
| a | b |
+----+---------+
| 10 | test-10 |
| 20 | test-20 |
| 30 | test-30 |
+----+---------+
apache drill 1.17> SELECT *, drilltypeof(c), modeof(c) FROM
dfs.test.`f*.parquet`;
+------------+----+---------+-------+---------+----------+
| dir0 | a | b | c | EXPR$1 | EXPR$2 |
+------------+----+---------+-------+---------+----------+
| f1.parquet | 1 | test-1 | other | VARCHAR | NULLABLE |
| f1.parquet | 2 | test-2 | null | VARCHAR | NULLABLE |
| f1.parquet | 3 | test-3 | old | VARCHAR | NULLABLE |
| f2.parquet | 10 | test-10 | null | VARCHAR | NULLABLE |
| f2.parquet | 20 | test-20 | null | VARCHAR | NULLABLE |
| f2.parquet | 30 | test-30 | null | VARCHAR | NULLABLE |
+------------+----+---------+-------+---------+----------+
{code}
It will be nice to know when 'c' data is present because the column exists in
the Parquet (or other type file) or if the value NULL was generated because
the column was missing.
Example a function 'origin' that take a column name and return for each row if
the value was 'generated' or 'original' (other/better keyword could be choose)
Virtual Example with previous data:
{code:sql}
apache drill> SELECT *, drilltypeof(c), modeof(c), origin(c) AS origin FROM
dfs.test.`f*.parquet`;
+------------+----+---------+-------+---------+----------+-----------+
| dir0 | a | b | c | EXPR$1 | EXPR$2 | origin |
+------------+----+---------+-------+---------+----------+-----------+
| f1.parquet | 1 | test-1 | other | VARCHAR | NULLABLE | original |
| f1.parquet | 2 | test-2 | null | VARCHAR | NULLABLE | original |
| f1.parquet | 3 | test-3 | old | VARCHAR | NULLABLE | original |
| f2.parquet | 10 | test-10 | null | VARCHAR | NULLABLE | generated |
| f2.parquet | 20 | test-20 | null | VARCHAR | NULLABLE | generated |
| f2.parquet | 30 | test-30 | null | VARCHAR | NULLABLE | generated |
+------------+----+---------+-------+---------+----------+-----------+
{code}
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