You can use a sequence to generate values that are unique across multiple tables or that are different from a set of natural numbers. A sequence is created using the CREATE SEQUENCE statement. Sequence values are returned as BIGINT values.
For each connection, the most recent use of the next value is saved as the current value.
When you create a sequence, its definition includes the number of sequence values the database server holds in memory. When this cache is exhausted, the sequence cache is repopulated. If the database server fails, then sequence values that were held in the cache may be skipped.
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