[Datafusion] Datafusion queries involving a column name that begins with a number produces unexpected results

[alamb]

Note: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-10329

This bug can be worked around by wrapping column names in quotes.

Example:

{{let query = "SELECT 16_20mph, 21_25mph FROM foo;"}}

{{let logical_plan = ctx.create_logical_plan(query)?;}}

{{logical_plan.schema().fields() now has fields: [_20mph, _25mph]}}

The resulting table produced by this query looks like:
||{{_20mph}}||{{_25mph}}||
|16|21|
|16|21|

Every row is identical, where the column value is equal to the initial number that appears in the column name.

[alamb]

Comment from Ben Sully(sd2k) @ 2020-11-08T11:46:18.008+0000:

This behaviour seems consistent with Postgres at least:


{{❯ psql}}
{{psql (12.4)}}
{{Type "help" for help.}}

{{ben=# create table foo ("16_20mph" integer, "21_25mph" integer);}}
{{CREATE TABLE}}
{{ben=# insert into foo values (1, 2), (3, 4);}}
{{INSERT 0 2}}
{{ben=# SELECT 16_20mph, 21_25mph FROM foo;}}
{{ _20mph | _25mph }}
{{--------+--------}}
{{ 16 | 21}}
{{ 16 | 21}}
{{(2 rows)}}

{{ben=# SELECT "16_20mph", "21_25mph" FROM foo;}}
{{ 16_20mph | 21_25mph }}
{{----------+----------}}
{{ 1 | 2}}
{{ 3 | 4}}
{{(2 rows)}}

[Jefffrey]

I believe this can be closed as its expected behaviour stemming from sqlparser, recent relevant discussion: apache/datafusion-sqlparser-rs#768 (comment)

[alamb]

I agree -- thanks @Jefffrey -- I agree this is "expected behavior" in the sense that it is what postgres does even though it is not very obvious