CHAR/VARCHAR fields sometimes show as STRING in a view

kmenke-em — Thu, 12 Jun 2025 19:42:48 GMT

We've found an interesting behavior where `char` and `varchar` fields in a table show as the `string` type in a view. Consider the following table and view:

create or replace table thirty_day_tables.kit_varchar_string ( str1 string, str2 char(10), str3 varchar(10) ); create or replace view thirty_day_tables.kit_varchar_string_vw as select str1, str2, str3, cast("dummy" as varchar(10)) as str4 from thirty_day_tables.kit_varchar_string;

In this case, it mostly works as I expected except for the manufactured field `str4`. The output for `

describe thirty_day_tables.kit_varchar_string_vw`:

col_name	data_type	comment
str1	string	null
str2	char(10)	null
str3	varchar(10)	null
str4	string	null

Why does str4 show as a string despite the explicit cast to a varchar(10)?

Even stranger, if I add a comment to each column I get a different result:

create or replace view thirty_day_tables.kit_varchar_string_vw ( str1 comment "OK - expected to be a string in the view", str2 comment "ERROR - expected to be a char(10) in the view", str3 comment "ERROR - expected to be a varchar(10) in the view", str4 comment "ERROR - expected to be a varchar(10) in the view" ) as select str1, str2, str3, cast("dummy" as varchar(10)) as str4 from thirty_day_tables.kit_varchar_string;

The output for `describe thirty_day_tables.kit_varchar_string_vw`:

col_name	data_type	comment
str1	string	OK - expected to be a string in the view
str2	string	ERROR - expected to be a char(10) in the view
str3	string	ERROR - expected to be a varchar(10) in the view
str4	string	ERROR - expected to be a varchar(10) in the view

Why do all the columns show as string???

Re: CHAR/VARCHAR fields sometimes show as STRING in a view

UmaMahesh1 — Thu, 12 Jun 2025 20:01:04 GMT

In Spark SQL

string is the canonical type for all textual data.
char(n) and varchar(n) are parsed and stored as metadata, but internally treated as string.
When you create a view, Spark does not preserve the original char(n) or varchar(n) types — it normalizes everything to string.

This is why:

In your first view (without comments), Spark is able to preserve the metadata from the underlying table for str2 and str3.
But when you add column comments, Spark reconstructs the schema from the SELECT clause and drops the original metadata, defaulting all string-like types to string.

topic Re: CHAR/VARCHAR fields sometimes show as STRING in a view in Data Engineering

CHAR/VARCHAR fields sometimes show as STRING in a view

Re: CHAR/VARCHAR fields sometimes show as STRING in a view