You can set options at three levels of scope:
Temporary options take precedence over user and PUBLIC settings. User level options take precedence over PUBLIC settings. If you set a user level option for the current user, the corresponding temporary option is set as well.
Some options (such as COMMIT behavior) are database-wide in scope. Setting these options requires specific privileges. Other options, such as the isolation_level option, can be applied to just the current connection and need no special privileges.
Changes to option settings take place at different times, depending on the option. Changing a global option such as the recovery_time option takes place the next time the database is started. Generally, only options that affect the current connection occur immediately. For example, you can change option settings in the middle of a transaction.
Do not change option values while a cursor is open. Changing the option values while a cursor is open can lead to inconsistent results within the cursor. For example, changing the date_format option while a cursor is open can result in some rows being returned in the old format and some rows returned in the new format. To ensure that the rows in the result set are computed consistently using the new option value, open the cursor after the option value is changed.
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