From 44f7afba79348883da110642d230a13003b75f62 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Wed, 4 Jan 2017 16:30:16 -0500 Subject: [PATCH] Improve documentation of timestamp internal representation. Be more clear that we represent timestamps in microseconds when integer timestamps are used, and in fractional seconds when floating-point timestamps are used. Discussion: http://postgr.es/m/20161212135045.GB15488@e733.localdomain Report by Alexander Alekseev. Wording by me with a suggestion from Tom Lane. --- doc/src/sgml/datatype.sgml | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 464ce83d30..3bc6854be6 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1651,13 +1651,14 @@ SELECT E'\\xDEADBEEF'; When timestamp values are stored as eight-byte integers (currently the default), microsecond precision is available over - the full range of values. When timestamp values are - stored as double precision floating-point numbers instead (a - deprecated compile-time option), the effective limit of precision - might be less than 6. timestamp values are stored as - seconds before or after midnight 2000-01-01. When - timestamp values are implemented using floating-point - numbers, microsecond precision is achieved for dates within a few + the full range of values. In this case, the internal representation + is the number of microseconds before or after midnight 2000-01-01. + When timestamp values are stored as double precision + floating-point numbers (a deprecated compile-time option), the + internal representation is the number of seconds before or after + midnight 2000-01-01. With this representation, the effective limit + of precision might be less than 6; in practice, + microsecond precision is achieved for dates within a few years of 2000-01-01, but the precision degrades for dates further away. Note that using floating-point datetimes allows a larger range of timestamp values to be represented than -- 2.40.0