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PostgreSQL Reference Manual

Volume 1: SQL Language Reference

for version 8.2.4.

June 2007

The PostgreSQL Global Development Group

(1) Actually, PostgreSQL uses the default B-tree operator class for the expression's data type to determine the sort ordering for ASC and DESC. Conventionally, data types will be set up so that the < and > operators correspond to this sort ordering, but a user-defined data type's designer could choose to do something different.

(2) The conversion names follow a standard naming scheme: The official name of the source encoding with all non-alphanumeric characters replaced by underscores followed by _to_ followed by the equally processed destination encoding name. Therefore the names might deviate from the customary encoding names.

(3) 60 if leap seconds are implemented by the operating system

(4) Essentially, a predicate-locking system prevents phantom reads by restricting what is written, whereas MVCC prevents them by restricting what is read.

(5) Examples in this section are drawn from the regression test database after doing a VACUUM ANALYZE, using 8.2 development sources. You should be able to get similar results if you try the examples yourself, but your estimated costs and row counts will probably vary slightly because ANALYZE's statistics are random samples rather than being exact.

(6) You can get the effect of disabling foreign keys by using the --disable-triggers option--but realize that that eliminates, rather than just postponing, foreign key validation, and so it is possible to insert bad data if you use it.

ISBN 0954612027PostgreSQL Reference Manual - Volume 1 - SQL Language ReferenceSee the print edition