I'm trying to replicate few tables from one server to another using foreign data wrappers and creating materialized views on foreign tables but it's not real time. How can I replicate it real time, upgrading or other replication tools is not an option.
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I've created a DMS task of CDC and Full Load, migrating data from postgres 14 to Redshift. According to the documentation, when using pglogical and creating postgres publication with 'publish_via_partition_root' parameter of my partitioned table, changes should be published to the parent table and to to child tables. However, the data is still migrated to the child tables in Redshift and not to the parent table. Am I missing something thats needs to be configured or is it just not possible in DMS?
I have a use case where I am splitting one service into multiple and want to migrate tables (with huge data) from one RDS Postgres schema to another within the same DB Instance with ongoing replication and ~zero downtime, I am exploring AWS DMS service, I can see it is possible to migrate the entire DB, is it possible to migrate only a specific schema and how?
Using alter table query is not an option because I cannot move the table in one shot in production, it needs to happen gradually. An AWS DMS-like solution will fit the use-case.
Thanks in advance.
Moving a table from one schema to another schema, can be done by just altering the schema:
ALTER TABLE [ IF EXISTS ] name
SET SCHEMA new_schema
I have created a db long ago using django. Now as we are migrating the application, so I need all the CREATE TABLE sql queries which django might have run to create the entire db for our service (which has around 70-80 tables and each table has avg 30-70 columns).
Both the servers old and new are using Postgres for databases.
But the technology stack is completely different (A 3rd party proprietary application which will host the service) instead of django.
If I start to write all the tables again from scratch, it will take at least a week or two.
Is there any way either from Postgres or from django which can generate the CREATE TABLE sql schema for an entire db keeping all the relationship as is?
Also, I have to do minor modification to that schema as per customer requirement.
p.s - pg_dump won't work as I need actual schema itself to get it reviewed from client.
I need to create a slave for BI purposes and I need to modify some tables (e.g., remove all passwords or sensitive data). My database is PostgreSQL. I wonder if I can do it in database layer or I should do it programmatically by writing a code to do the replication.
You could use logical replication and have replica enabled triggers (that fire ony on replication) that modify the data when they are applied:
ALTER TABLE mytab DISABLE TRIGGER mytrig;
ALTER TABLE mytab ENABLE REPLICA TRIGGER mytrig;
You have to make sure that no replication conflicts can arise from these modifications. For example, never modify a key column.
Replication conflicts would stop replication and break your system.
The traditional way to solve this problem is to use an ETL process. That way you can have a different data model on the target database and for example pre-aggregate data so that the data warehouse doesn't grow too big and has a data model optimized for analytical queries.
I'd like to preface this by saying I'm not a DBA, so sorry for any gaps in technical knowledge.
I am working within a microservices architecture, where we have about a dozen or applications, each supported by its Postgres database instance (which is in RDS, if that helps). Each of the microservices' databases contains a few tables. It's safe to assume that there's no naming conflicts across any of the schemas/tables, and that there's no sharding of any data across the databases.
One of the issues we keep running into is wanting to analyze/join data across the databases. Right now, we're relying on a 3rd Party tool that caches our data and makes it possible to query across multiple database sources (via the shared cache).
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Are there any other ways to configure Postgres or RDS to make joining across our databases possible?
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Yes, that's possible and it's actually quite easy.
Setup one Postgres server that acts as the master.
For each remote server, create a foreign server then you then use to create a foreign table that makes the data accessible from the master server.
If you have multiple tables in multiple server that should be viewed as a single table in the master, you can setup inheritance to make all those tables appear like one. If you can define a "sharding" key that identifies a distinct attribute between those server, you can even make Postgres request the data only from the specific server.
All foreign tables can be joined as if they were local tables. Depending on the kind of query, some (or a lot) of the filter and join criteria can even be pushed down to the remote server to distribute the work.
As the Postgres Foreign Data Wrapper is writeable, you can even update the remote tables from the master server.
If the remote access and joins is too slow, you can create materialized views based on the remote tables to create a local copy of the data. This however means that it's not a real time copy and you have to manage the regular refresh of the tables.
Other (more complicated) options are the BDR project or pglogical. It seems that logical replication will be built into the next Postgres version (to be released a the end of this year).
Or you could use a distributed, shared-nothing system like Postgres-XL (which probably is the most complicated system to setup and maintain)