Add parsing support for Postgres "EXPLAIN" statement

[roblevy]

The first example from the Postgres EXPLAIN docs is:

EXPLAIN SELECT * FROM foo;

Expected Behaviour

>>> sqlfluff.parse("EXPLAIN SELECT * FROM foo;", dialect="postgres")
ParsedString(...)

Observed Behaviour

SQLParseError: Found unparsable section: 'EXPLAIN SELECT * FROM foo'

Steps to Reproduce

import sqlfluff
sqlfluff.parse("EXPLAIN SELECT * FROM foo;", dialect="postgres")

Version

sqlfluff: 0.4.1
Python: 3.8.6

Configuration

No configuration file.

[alanmcruickshank]

@roblevy , thanks for the Issue report! We might have to implement this seperately for different dialects, each one seems to have a slightly different syntax. So that we cover your use case, which dialects are you most likely to use?

Docs for reference:

• mysql: https://dev.mysql.com/doc/refman/5.7/en/explain.html
• postgres: https://www.postgresql.org/docs/9.1/sql-explain.html
• snowflake https://docs.snowflake.com/en/sql-reference/sql/explain.html
• bigquery doesn't even support it 🤷 https://cloud.google.com/bigquery/query-plan-explanation

[roblevy]

Hi Alan, Thanks for responding so quickly! We're using Postgres over here... Thanks Rob

…

On Fri, 26 Mar 2021, 11:01 Alan Cruickshank, ***@***.***> wrote: @roblevy <https://github.com/roblevy> , thanks for the Issue report! We might have to implement this seperately for different dialects, each one seems to have a slightly different syntax. So that we cover your use case, which dialects are you most likely to use? Docs for reference: - mysql: https://dev.mysql.com/doc/refman/5.7/en/explain.html - postgres: https://www.postgresql.org/docs/9.1/sql-explain.html - snowflake https://docs.snowflake.com/en/sql-reference/sql/explain.html - bigquery doesn't even support it 🤷 https://cloud.google.com/bigquery/query-plan-explanation — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#893 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABELHV2FV2GXXQ3UBB2UFETTFRSPFANCNFSM4Z2IJHFA> .

[dmateusp]

@alanmcruickshank I ended up implementing the MySQL flavor as ANSI (it's the simplest case), and separately implemented a Snowflake and Postgres version, with Postgres being the most complicated (I actually had to spin up a Postgres on Docker to wrap my head around what's valid there)

#951