Feature/information schema support

[iPeluwa]

@sunng87

Add information_schema support and enhance PostgreSQL compatibility

• Added information_schema.schemata, tables, and columns in information_schema.rs for schema introspection using DataFusion catalogs.
• Integrated information_schema queries in handlers.rs with schemata_df, tables_df, and columns_df.
• Implemented mock pg_catalog.pg_namespace in handlers.rs to return catalog_name, improving pgcli compatibility.
• Enhanced handlers.rs with SHOW search_path support, returning catalog_name as the search path.
• Refined query qualification in do_query to exclude information_schema and pg_catalog, preventing planning errors.
• Added debug logging in handlers.rs for incoming queries (requires log dependency).
• Updated main.rs with basic table registration and catalog name handling, setting the stage for further enhancements.
• Updated datafusion-postgres/Cargo.toml to include log dependency for debugging.

Note: main.rs still uses println! and lacks log integration; to be addressed in a future commit.

[sunng87]

Awesome! This looks great to me. Thank you @iPeluwa for this great patch!

[sunng87]

We'd better use arrow re-exported from datafusion. Otherwise we will have to trace arrow compatibility with datafusion.

[iPeluwa]

Oh yes, definitely agree with you.

[sunng87]

The integration test is broken. It seems we can no longer access the table from default catalog/schema.

Also it would be nice if you can include some integration tests for show statements and information_schema

[iPeluwa]

The integration test is broken. It seems we can no longer access the table from default catalog/schema.

Also it would be nice if you can include some integration tests for show statements and information_schema

Yes ofcourse, I'd fix this and push in a bit

[sunng87]

@iPeluwa just connect you on linkedin. I'm curious about your use of this library (I guess you are using it in a project, right?). We can talk more about this.

[iPeluwa]

@iPeluwa just connect you on linkedin. I'm curious about your use of this library (I guess you are using it in a project, right?). We can talk more about this.

Yes Definitely.

[gauravverma]

Hi @sunng87 !

Is there any plan to merge this? If there is any more capabilities required for this to be merged, maybe me and my team can contribute. Would love to hear your thoughts.

[sunng87]

We just need to get CI pass.

@iPeluwa do you have time working on this? I can pick this up and move on.

[iPeluwa]

We just need to get CI pass.

@iPeluwa do you have time working on this? I can pick this up and move on.

Yeah I would work on the CI passing today

[sunng87]

@iPeluwa I just merged this in #71. I will do some refactoring in near future. Thank you so much for the contribution!

[iPeluwa]

@sunng87 Currently working on this at the moment.

[sunng87]

@iPeluwa No problem. You can rebase to master and create a new PR. Thank you!