![]() For this reason, appropriate vacuum and analyze operations should be performed via session SQL commands. The autovacuum daemon cannot access and therefore cannot vacuum or analyze temporary tables. Any indexes created on a temporary table are automatically temporary as well. The default search_path includes the temporary schema first and so identically named existing permanent tables are not chosen for new plans while the temporary table exists, unless they are referenced with schema-qualified names. Temporary tables are automatically dropped at the end of a session, or optionally at the end of the current transaction (see ON COMMIT below). If specified, the table is created as a temporary table. To be able to create a table, you must have USAGE privilege on all column types or the type in the OF clause, respectively. Every column constraint can also be written as a table constraint a column constraint is only a notational convenience for use when the constraint only affects one column. A table constraint definition is not tied to a particular column, and it can encompass more than one column. A column constraint is defined as part of a column definition. There are two ways to define constraints: table constraints and column constraints. A constraint is an SQL object that helps define the set of valid values in the table in various ways. The optional constraint clauses specify constraints (tests) that new or updated rows must satisfy for an insert or update operation to succeed. Therefore, tables cannot have the same name as any existing data type in the same schema. The name of the table must be distinct from the name of any other relation (table, sequence, index, view, materialized view, or foreign table) in the same schema.ĬREATE TABLE also automatically creates a data type that represents the composite type corresponding to one row of the table. Temporary tables exist in a special schema, so a schema name cannot be given when creating a temporary table. Otherwise it is created in the current schema. ) then the table is created in the specified schema. If a schema name is given (for example, CREATE TABLE myschema.mytable. The table will be owned by the user issuing the command. Read the detailed explanation over there and pick the approach that best fits your use case.CREATE ĬREATE TABLE will create a new, initially empty table in the current database. Especially if the row frequently already exists, this is a bit faster. So here the overhead is slightly smaller (simpler queries), but the time frame for a race condition is slightly bigger. The alternative with CTEs runs as one SQL statement. This is assuming a UNIQUE constraint (or a UNIQUE index) on email, obviously. You only need the loop to deal with a possible race condition: If a concurrent transaction writes the same email value in between SELECT and INSERT, you would get a unique violation - which is handled properly here. ![]() ![]() ![]() ![]() RAISE NOTICE 'It actually happened!' - hardly ever happensĮXIT WHEN email_id IS NOT NULL - else keep looping RETURNING mailing_list.email_id INTO email_id ĮXCEPTION WHEN UNIQUE_VIOLATION THEN - inserted in concurrent session. INSERT INTO mailing_list (email) VALUES (_email) SELECT INTO email_id m.email_id FROM mailing_list m WHERE m.email = _email Is SELECT or INSERT in a function prone to race conditions?ĬREATE OR REPLACE FUNCTION f_email_insel(_email text, OUT email_id int) ASīEGIN - start inner block inside loop to handle possible exception.Here is a simple variant of the related version we have been referring to: Already explained how to avoid the error message you saw. ![]()
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