Document DEFAULT keyword as a reserved term

[jhlodin]

Description

DEFAULT is used as a keyword in Trino, at least in SET PARAMETERS clauses to revert a parameter back to its default value. It ought to be documented accordingly.

Is this change a fix, improvement, new feature, refactoring, or other?

Improvement

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

Documentation

How would you describe this change to a non-technical end user or system administrator?

Documenting the DEFAULT SQL keyword in Trino

Related issues, pull requests, and links

• Fixes Document support of DEFAULT keyword in properties #10869
• Should be merged in conjunction with Document support for ALTER TABLE SET PROPERTIES #11022
• Following up on Document ALTER MATERIALIZED VIEW SET PROPERTIES #10835

Documentation

( ) No documentation is needed.
(x) Sufficient documentation is included in this PR.
( ) Documentation PR is available with #prnumber.
( ) Documentation issue #issuenumber is filed, and can be handled later.

Release notes

(x) No release notes entries required.
( ) Release notes entries required with the following suggested text:

# Section
* Fix some things. ({issue}`issuenumber`)

[jhlodin]

I considered adding a note about using DEFAULT in the CREATE TABLE and CREATE TABLE AS pages, to say that you can use it to set a default column value when defining a column. But:

• I don't know if we actually support that in Trino
• Maybe that's too much of a SQL fundamentals thing that it's overkill for us to document

Thoughts?

[ebyhr]

DEFAULT isn't a reserved keyword in Trino at this time. That is why docs-checks job is failing.
https://github.com/trinodb/trino/blob/master/core/trino-parser/src/main/antlr4/io/trino/sql/parser/SqlBase.g4#L707-L712

[jhlodin]

Maybe I'm misunderstanding, I thought that DEFAULT being an accepted keyword in, at least, the ... SET PROPERTIES foo = DEFAULT context would mean that it's reserved?

[kasiafi]

We generally try not to make keywords reserved unless there's a potential ambiguity. I don't think that's the case with DEFAULT. Also, making it reserved would likely cause backwards-compatibility issues.

[findepi]

cc @martint @kasiafi

[jhlodin]

Closing as inaccurate

[kasiafi]

I considered adding a note about using DEFAULT in the CREATE TABLE and CREATE TABLE AS pages, to say that you can use it to set a default column value when defining a column. But:
I don't know if we actually support that in Trino

We don't support it.