NameCHECKPOINT -- force a transaction log checkpoint Synopsis CHECKPOINT Description A checkpoint is a point in the transaction log sequence at which all data files have been updated to reflect the information in the log. All data files will be flushed to disk. Refer to Section 30.4 for more details about what happens during a checkpoint. The CHECKPOINT command forces an immediate checkpoint when the command is issued, without waiting for a regular checkpoint scheduled by the system (

Namepg_test_fsync -- determine fastest wal_sync_method for PostgreSQL Synopsis pg_test_fsync [option...] Description pg_test_fsync is intended to give you a reasonable idea of what the fastest wal_sync_method is on your specific system, as well as supplying diagnostic information in the event of an identified I/O problem. However, differences shown by pg_test_fsync might not make any significant difference in real database throughput, especially since many database servers are not speed

The planner classifies operations involved in a query as either parallel safe, parallel restricted, or parallel unsafe. A parallel safe operation is one which does not conflict with the use of parallel query. A parallel restricted operation is one which cannot be performed in a parallel worker, but which can be performed in the leader while parallel query is in use. Therefore, parallel restricted operations can never occur below a Gather node, but can occur elsewhere in a plan which contains a

For enum types (described in Section 8.7), there are several functions that allow cleaner programming without hard-coding particular values of an enum type. These are listed in Table 9-32. The examples assume an enum type created as: CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple'); Table 9-32. Enum Support Functions Function Description Example Example Result enum_first(anyenum) Returns the first value of the input enum type enum_first(null::rainbow) red e

A column can be assigned a default value. When a new row is created and no values are specified for some of the columns, those columns will be filled with their respective default values. A data manipulation command can also request explicitly that a column be set to its default value, without having to know what that value is. (Details about data manipulation commands are in Chapter 6.) If no default value is declared explicitly, the default value is the null value. This usually makes sense be

PostgreSQL is a relational database management system (RDBMS). That means it is a system for managing data stored in relations. Relation is essentially a mathematical term for table. The notion of storing data in tables is so commonplace today that it might seem inherently obvious, but there are a number of other ways of organizing databases. Files and directories on Unix-like operating systems form an example of a hierarchical database. A more modern development is the object-oriented database

Recall the weather and cities tables from Chapter 2. Consider the following problem: You want to make sure that no one can insert rows in the weather table that do not have a matching entry in the cities table. This is called maintaining the referential integrity of your data. In simplistic database systems this would be implemented (if at all) by first looking at the cities table to check if a matching record exists, and then inserting or rejecting the new weather records. This approach has a

NameALTER EVENT TRIGGER -- change the definition of an event trigger Synopsis ALTER EVENT TRIGGER name DISABLE ALTER EVENT TRIGGER name ENABLE [ REPLICA | ALWAYS ] ALTER EVENT TRIGGER name OWNER TO { new_owner | CURRENT_USER | SESSION_USER } ALTER EVENT TRIGGER name RENAME TO new_name Description ALTER EVENT TRIGGER changes properties of an existing event trigger. You must be superuser to alter an event trigger. Parameters name The name of an existing trigger to alter. new_owner

NameDROP TABLESPACE -- remove a tablespace Synopsis DROP TABLESPACE [ IF EXISTS ] name Description DROP TABLESPACE removes a tablespace from the system. A tablespace can only be dropped by its owner or a superuser. The tablespace must be empty of all database objects before it can be dropped. It is possible that objects in other databases might still reside in the tablespace even if no objects in the current database are using the tablespace. Also, if the tablespace is listed in the t

The pg_enum catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in pg_enum. Table 50-20. pg_enum Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) enumtypid oid pg_type.oid The OID of the pg_type entry owning this enum value enumsortorder float4 The sort position of this enum value within its enum type enumlabel na