What is pt-archiver?
DESCRIPTION. pt-archiver is the tool I use to archive tables as described in http://tinyurl.com/mysql-archiving. The goal is a low-impact, forward-only job to nibble old data out of the table without impacting OLTP queries much. You can insert the data into another table, which need not be on the same server.
How does PT-Archiver work?
How does pt-archiver select records to archive? Pt-archiver uses the index to select records from the table. The index is used to optimize repeated accesses to the table. Pt-archiver remembers the last row it retrieves from each SELECT statement, and uses it to construct a WHERE clause.
What are foreign keys in Postgres?
Introduction to PostgreSQL Foreign Key Constraint A foreign key is a column or a group of columns in a table that reference the primary key of another table. The table that contains the foreign key is called the referencing table or child table.
Are foreign keys automatically unique?
2 Answers. All databases allow foreign keys to be NULLable and non-UNIQUE. How you choose to declare a particular foreign key depends on the business case.
Which is the referenced table with the foreign key?
The table that contains the foreign key is called the referencing table or child table. And the table referenced by the foreign key is called the referenced table or parent table. A table can have multiple foreign keys depending on its relationships with other tables. In PostgreSQL, you define a foreign key using the foreign key constraint.
How to create and manage foreign key relationships?
When you use this syntax, Cloud Spanner generates a name for you. To discover the names of all foreign keys, refer to View properties of a foreign key relationship. We also want to make sure that orders can only be created for products that exist. We’ll use ALTER TABLE to add another foreign key constraint to the orders table as follows:
Is it good to always index foreign keys?
That’s a good sign, though. Our foreign key is strong. Strong like lab rat. Even with no supporting indexes, we can still get join elimination. And this makes total sense. The constraint is there, and it’s trusted. Maybe the advice to always index foreign keys is more like “usually” or “it depends”.
Why do you need a foreign key in PostgreSQL?
A table can have multiple foreign keys depending on its relationships with other tables. In PostgreSQL, you define a foreign key using the foreign key constraint. The foreign key constraint helps maintain the referential integrity of data between the child and parent tables.