I would like to obtain from database B, by querying its database tables, the original schemas and table names of its foreign tables (i.e. those in the original database A where they actually reside, as their name can be changed when created with the available fdw).
Any hint greatly appreciated!
Currently I am only able to find columns names and datatypes of the foreign tables (in database B) ...
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I've got PostgreSQL DB with multiple schemas and tables in that schemas. Every row in table have PRIMARY UUID like "Ref_Key" => "41bf3b1e-91f0-491c-a6bd-c48a17e7c252"
Is it possible to find row only by it UUID, without specifying schema and table?
No, that is not possible. You can only query tables that explicitly appear in the FROM clause of a SELECT statement.
I'm new to DBIC. I've imported data into a database. It's not possible to create relationships between the tables because, apparently, not all the values in the child table's foreign key column have a corresponding value in the parent table.
So is it possible to still do joins between the tables? I've skimmed through the tutorial and documentation but found nothing that addresses this problem.
You can of course define relationships in your DBIC schema that don't have a matching constraint in the database.
If you use $schema->deploy it will automatically generate constraints for all foreign key columns.
We have two copies of a simple application that is based on SQLite. The application has 10 tables with a variety of relations between the tables. We would like to merge the databases to a single Postgres database with the same schema. We can use Talend to facilitate this, however the issue is that there would be duplicate keys (as both the source databases are independent). Is there a systematic method by which we can insert data into Postgres with the original key plus an offset resulting from loading the first database?
Step 1. Restore the first database.
Step 2. Change foreign keys of all tables by adding the option on update cascade.
For example, if the column table_b.a_id refers to the column table_a.id:
alter table table_b
drop constraint table_b_a_id_fkey,
add constraint table_b_a_id_fkey
foreign key (a_id) references table_a(id)
on update cascade;
Step 3. Update primary keys of the tables by adding the desired offset, e.g.:
update table_a
set id = 10000+ id;
Step 4. Restore the second database.
If you have the possibility to edit the script with database schema (or do the transfer manually with your own script), you can merge steps 1 and 2 and edit the script before the restore (adding the option on update cascade for foreign keys in tables declarations).
I was wondering, if it is possible to have two temp tables with the same name in two separate queries without them conflicting when called upon later in the queries.
Query 1: Create Temp Table Tmp1 as ...
Query 2: Create Temp Table Tmp1 as ...
Query 1: Do something with Tmp1 ...
I am wondering if postgresql distinguishes between those two tables, maybe through addressing them as Query1.Tmp1 and Query2.Tmp1
Each connection to the database gets its own special temporary schema name, and temp tables are created in that schema. So there will not be any conflict between concurrent queries from separate connections, even if the tables have the same names. https://dba.stackexchange.com/a/5237 for more info
The PostgreSQL docs for creating tables states:
Temporary tables exist in a special schema, so a schema name cannot be given when creating a temporary table.
How to get exported keys (database metadata).Even though redshift does not support foreign keys and primary keys I am able to see them in system tables.
The problem here is in the system table the multiple columns of a foreign key exist as an array in one column(though redshift doesn't support arrays). Is it possible to extract them in one query.
Use table_constraints table:
SELECT * FROM information_schema.table_constraints;