Support DESCRIBE TABLE syntax

[dejanmltc]

Reference: https://clickhouse.com/docs/sql-reference/statements/describe-table

This PR updates the SQL parser to handle the official ClickHouse
DESCRIBE TABLE <table_name> syntax.

Previously, only DESCRIBE <table_name> was supported. With this change,
the parser now also accepts DESCRIBE TABLE <table_name>, which is the
syntax described in the official documentation.

Changes:

• Extend grammar to allow the optional TABLE keyword in DESCRIBE statements.
• Ensure both DESCRIBE <table_name> and DESCRIBE TABLE <table_name> parse correctly.
• Add or update tests to cover both forms.

Justification:

• The parser should fully align with ClickHouse’s supported syntax.
• This ensures compatibility with both the documented standard form
  (DESCRIBE TABLE) and the commonly used shorthand (DESCRIBE).

[Copilot]

Pull Request Overview

This PR enforces the official ClickHouse DESCRIBE TABLE syntax by requiring the TABLE keyword after DESC/DESCRIBE statements. The change ensures the parser strictly follows ClickHouse's documented syntax instead of accepting the invalid DESCRIBE <table_name> form.

• Updated parser to require TABLE keyword after DESC/DESCRIBE
• Added DescribeType field to track the describe statement type
• Updated all test files to use the correct DESCRIBE TABLE syntax

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
parser/ast.go	Added DescribeType field to DescribeStmt struct and updated String() method
parser/parser_table.go	Added validation to require TABLE keyword after DESC/DESCRIBE
parser/testdata/ddl/describe_table.sql	Updated test case to use DESCRIBE TABLE syntax
parser/testdata/ddl/desc_table.sql	Updated test case to use DESC TABLE syntax
parser/testdata/ddl/format/describe_table.sql	Updated expected format output for DESCRIBE TABLE
parser/testdata/ddl/format/desc_table.sql	Updated expected format output for DESC TABLE
parser/testdata/ddl/output/describe_table.sql.golden.json	Updated golden test output with new positions and DescribeType field
parser/testdata/ddl/output/desc_table.sql.golden.json	Updated golden test output with new positions and DescribeType field

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[coveralls]

Pull Request Test Coverage Report for Build 17151399017

Details

• 11 of 11 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 50.363%

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Totals
Change from base Build 16988786925:	0.03%
Covered Lines:	7358
Relevant Lines:	14610

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💛 - Coveralls

[git-hulk]

@dejanmltc Thanks for your fix.

From the ClickHouse antlr, it looks like the keyword TABLE is optional for DESCRIBE|DESC statement. I tried it at the ClickHouse playground and confirmed it's a valid syntax by omitting the keyword TABLE: https://sql.clickhouse.com/?query=REVTQyBhbWF6b24uYW1hem9uX3Jldmlld3M.

Would you mind making TABLE an option when parsing the statement?

[dejanmltc]

@git-hulk
Thanks for the clarification!
I’ve updated the PR so that TABLE is optional in the DESCRIBE statement.
Both DESCRIBE <table_name> and DESCRIBE TABLE <table_name> should now parse correctly.

[git-hulk]

@dejanmltc Thank you!