From 865d26fdd632890167035dac905b6379d4383209 Mon Sep 17 00:00:00 2001
From: Bruce Momjian Last updated: Thu Feb 14 12:14:47 EST 2002 Last updated: Mon Feb 18 00:08:54 EST 2002 Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) As an example, consider a file of 100,000 lines with an integer
and text description on each line. Suppose the text string avergages
- twenty characters in length. The flat file would be 2.8 MB. The size
+ twenty bytes in length. The flat file would be 2.8 MB. The size
of the PostgreSQL database file containing this data can be
- estimated as 6.6 MB:Frequently Asked Questions (FAQ) for PostgreSQL
-
@@ -855,27 +855,27 @@
36 bytes: each row header (approximate) - 26 bytes: two int fields @ 4 bytes each + 24 bytes: one int field and one text filed + 4 bytes: pointer on page to tuple ---------------------------------------- - 66 bytes per row + 64 bytes per row The data page size in PostgreSQL is 8192 bytes (8 KB), so: 8192 bytes per page - ------------------- = 124 rows per database page (rounded down) - 66 bytes per row + ------------------- = 128 rows per database page (rounded down) + 64 bytes per row 100000 data rows - -------------------- = 807 database pages (rounded up) - 124 rows per page + -------------------- = 782 database pages (rounded up) + 128 rows per page -807 database pages * 8192 bytes per page = 6,610,944 bytes (6.6 MB) +782 database pages * 8192 bytes per page = 6,406,144 bytes (6.4 MB)
Indexes do not require as much overhead, but do contain the data -- cgit v1.2.3