diff options
| author | Bruce Momjian | 2004-07-27 03:27:48 +0000 |
|---|---|---|
| committer | Bruce Momjian | 2004-07-27 03:27:48 +0000 |
| commit | b1ee93884d528672fbce446a38659954a86219e1 (patch) | |
| tree | 3cb6bcc06e85cba9e1825636472093b99141bde0 /doc/FAQ | |
| parent | 0177f430701744432e4b5c4e145cd669fd3054cf (diff) | |
Update tuple header size.
Diffstat (limited to 'doc/FAQ')
| -rw-r--r-- | doc/FAQ | 14 |
1 files changed, 7 insertions, 7 deletions
@@ -1,7 +1,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL - Last updated: Mon Jul 19 16:28:37 EDT 2004 + Last updated: Mon Jul 26 23:27:08 EDT 2004 Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) @@ -735,23 +735,23 @@ 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 6.4 MB: - 36 bytes: each row header (approximate) + 32 bytes: each row header (approximate) 24 bytes: one int field and one text field + 4 bytes: pointer on page to tuple ---------------------------------------- - 64 bytes per row + 60 bytes per row The data page size in PostgreSQL is 8192 bytes (8 KB), so: 8192 bytes per page - ------------------- = 128 rows per database page (rounded down) - 64 bytes per row + ------------------- = 136 rows per database page (rounded down) + 60 bytes per row 100000 data rows - -------------------- = 782 database pages (rounded up) + -------------------- = 735 database pages (rounded up) 128 rows per page -782 database pages * 8192 bytes per page = 6,406,144 bytes (6.4 MB) +735 database pages * 8192 bytes per page = 6,021,120 bytes (6 MB) Indexes do not require as much overhead, but do contain the data that is being indexed, so they can be large also. |