Re: [GENERAL] Enum in foreign table: error and correct way to handle.
Thank you for the message Tom; sounds great. I'll try that out, will check on the planner's resultant behavior and email back. Peter On Sat, May 23, 2015 at 12:35 PM, Tom Lane t...@sss.pgh.pa.us wrote: Peter Swartz peter.goodings.swa...@gmail.com writes: suppose the foreign database adds a value to the enum, and the foreign table now has rows with this new value, while the local definition of the enum remains unchanged. Obviously, the appropriate action on my part is to maintain consistency of enum definition between the foreign and local database, but I'm curious about what behavior would result if there was an error in this manual updating process. What I'd expect to happen is that you'd get errors when retrieving rows that had the values not known on the local side. One potential way around this is to declare the foreign table's columns as text rather than enums; you would lose some error checking on the local side, but the remote server would enforce validity whenever you stored something. (But I'm not sure whether this hack behaves desirably for WHERE conditions on the enum column; you'd need to test.) regards, tom lane
Re: [GENERAL] Enum in foreign table: error and correct way to handle.
Thank you for the note Ian. I definitely see your point about the onus being on the local database to maintain the definition of the remote table. Do you or anyone have this list have any experience with the resulting behavior if the definition of the enum were to become out of sync between the local database and the foreign database? In other words, suppose the foreign database adds a value to the enum, and the foreign table now has rows with this new value, while the local definition of the enum remains unchanged. Obviously, the appropriate action on my part is to maintain consistency of enum definition between the foreign and local database, but I'm curious about what behavior would result if there was an error in this manual updating process. I may dig into this a bit further myself in a few test databases, to see what happens. Will post a response if I do. With regards, Peter On Thu, May 21, 2015 at 8:06 PM, Ian Barwick i...@2ndquadrant.com wrote: On 21/05/15 04:23, Peter Swartz wrote: I'm creating a foreign table (foo_table) in database_a. foo_table lives in database_b.foo_table has an enum (bar_type) as one of its columns. Because this enum is in database_b, the creation of the foreign table fails in database_a. database_a doesn't understand the column type. Running the following in database_a CREATE FOREIGN TABLE foo_table (id integer NOT NULL, bar bar_type) SERVER database_b One gets the error: ERROR: type bar_type does not exist I could just create a copy of bar_type in database_a, but this feels duplicative and possibly a future cause of inconsistency / trouble. Would anyone have thoughts on best practices for handling? A foreign table is basically an ad-hoc remote data source for the local database, so the onus is on the local database to maintain its definition of the remote table, whether it's in another (or even the same) PostgreSQL server or a completely different data source, especially as the local definition can be different from the remote one. This does mean that there's no simple way of ensuring any remote dependencies are present on the local server. PostgreSQL 9.5 will provide the IMPORT FOREIGN SCHEMA command, however this is limited to table/view definitions. Regards Ian Barwick -- Ian Barwick http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training Services
Re: [GENERAL] Enum in foreign table: error and correct way to handle.
Peter Swartz peter.goodings.swa...@gmail.com writes: suppose the foreign database adds a value to the enum, and the foreign table now has rows with this new value, while the local definition of the enum remains unchanged. Obviously, the appropriate action on my part is to maintain consistency of enum definition between the foreign and local database, but I'm curious about what behavior would result if there was an error in this manual updating process. What I'd expect to happen is that you'd get errors when retrieving rows that had the values not known on the local side. One potential way around this is to declare the foreign table's columns as text rather than enums; you would lose some error checking on the local side, but the remote server would enforce validity whenever you stored something. (But I'm not sure whether this hack behaves desirably for WHERE conditions on the enum column; you'd need to test.) regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] Enum in foreign table: error and correct way to handle.
On 21/05/15 04:23, Peter Swartz wrote: I'm creating a foreign table (foo_table) in database_a. foo_table lives in database_b.foo_table has an enum (bar_type) as one of its columns. Because this enum is in database_b, the creation of the foreign table fails in database_a. database_a doesn't understand the column type. Running the following in database_a CREATE FOREIGN TABLE foo_table (id integer NOT NULL, bar bar_type) SERVER database_b One gets the error: ERROR: type bar_type does not exist I could just create a copy of bar_type in database_a, but this feels duplicative and possibly a future cause of inconsistency / trouble. Would anyone have thoughts on best practices for handling? A foreign table is basically an ad-hoc remote data source for the local database, so the onus is on the local database to maintain its definition of the remote table, whether it's in another (or even the same) PostgreSQL server or a completely different data source, especially as the local definition can be different from the remote one. This does mean that there's no simple way of ensuring any remote dependencies are present on the local server. PostgreSQL 9.5 will provide the IMPORT FOREIGN SCHEMA command, however this is limited to table/view definitions. Regards Ian Barwick -- Ian Barwick http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training Services -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
