SQL column identifiers should be converted to lowercase when unquoted #1746
Description
Is your feature request related to a problem or challenge? Please describe what you are trying to do.
DataFusion strives to implement a subset of the PostgreSQL SQL dialect where possible
In PostgreSQL all column name identifiers are turned into lowercase, unless they are quoted. Example:
tmp1=> create table blah (Foo int, "Foo" int, "Bar" int);
CREATE TABLE
tmp1=> \d blah
Table "public.blah"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
foo | integer | | |
Foo | integer | | |
Bar | integer | | |
tmp1=> insert into blah values (1,2,3);
INSERT 0 1
tmp1=> select foo, Foo, "Foo", "Bar" from blah;
foo | foo | Foo | Bar
-----+-----+-----+-----
1 | 1 | 2 | 3
(1 row)
tmp1=> select Bar from blah;
ERROR: column "bar" does not exist
LINE 1: select Bar from blah;
^
HINT: Perhaps you meant to reference the column "blah.Bar".
PostgreSQL converts to lowercase all column identifiers. The example above shows how Foo used in the DDL statement creates a column actually named foo and it shows how it can be accessed in a query with Foo (unquoted). An actual "Foo" column happily coexist with foo in the table, but must be referenced with a quoted "Foo"
In Datafusion currently Bar means the same as "Bar" (I'm not providing a screen dump of the current datafusion behaviour out of laziness, I may add it later if turns out to be useful for the discussion).
Describe the solution you'd like
select FoO from my_table;
should be equivalent to
select foo from my_table;
If users want to access a column that is not in lower case, they should explicitly quote the column:
select "FoO" from my_table;