Document schema size limitation in Postgres Source connector docs

[grishick]

Tell us about the documentation you'd like us to add or update.

Platform is currently not able to handle schemas larger than 4MB. This is a platform-wide limitation. However, it should be documented for GA connectors that are likely to produce such large schemas.

If applicable, add links to the relevant docs that should be updated

• Postgres Source docs page

[grishick]

To close this issue:

• identify the exact size limit
• create an approximate estimate in the form of "number of tables with average number of columns per table" that reflects the upper limit that source postgres connector can work with

[kimerinn]

@grishick , should this task be closed? I could not find any info about postgres table metadata size, so unfortunately, I could not define max number of tables/columns per table for 4Mb limit

[grishick]

@kimerinn could you do some testing to find an approximate number of columns x tables that would hit the limit? I could expect that if a schema is approaching some number X of columns across all tables it will start hitting this limit.

[kimerinn]

@grishick I added some rough calculations that I found playing with my Windows PostgreSQL 12. Review please
#14602