Does cstore_fdw get around Postgres 8kb row size limit?

[Lee Hachadoorian]

Postgres tables are limited to 250 - 1600 columns depending on data type and whether the data types are TOASTable. One advantage to column-store databases is that they can support wide tables. Therefore:

1) Is there a hard limit to the number of columns a cstore foreign table can have?
2) Is there a row size limit (Postgres' 8kb, or another limit imposed by cstore)?

[Murat Tuncer]

Hi Lee

1 - number of columns is limited by postgresql,  cstore_fdw itself does not impose any limits. 

2 - there is no preset limit on row size, however,  due to how cstore works,  active "stripe" has to fit in a work memory. If you are planning to use large rows you may hit out of memory issues. If that happens you can 

• reduce number of size in a stripe. Default is 150 000 rows, you should set server option "stripe_row_count" to a lower value when creating cstore table, or
• increase  work_mem  in postgresql configuration. Depending on how many concurrent connections you want to allow in you server you can even set it to order of GBs.

[Jose Sanchez]

Hey Mirat,

so there is no limit in the number of columns right? as long as I have enough memory.

Thanks!

[Murat Tuncer]

cstore itself does not enforce a maximum but PG limits column count to  1600. 

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