pg_lsn data type can be used to
store LSN (Log Sequence Number) data which is a pointer to a
location in the WAL. This type is a representation of
XLogRecPtr and an internal system type of
Internally, an LSN is a 64-bit integer, representing a byte
position in the write-ahead log stream. It is printed as two
hexadecimal numbers of up to 8 digits each, separated by a slash;
pg_lsn type supports the standard
comparison operators, like
>. Two LSNs can be subtracted using
- operator; the result is the
number of bytes separating those write-ahead log locations.
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