From fc9b6451a5ee4ae88cf751c7923f270dd50be0c1 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Thu, 1 Sep 2005 16:18:08 +0000
Subject: [PATCH] Update disk space computation because oids are now optional.
---
doc/FAQ | 16 ++++++++--------
doc/src/FAQ/FAQ.html | 16 ++++++++--------
2 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/doc/FAQ b/doc/FAQ
index 23994765bf4..dae4beef81d 100644
--- a/doc/FAQ
+++ b/doc/FAQ
@@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Thu Aug 11 09:21:58 EDT 2005
+ Last updated: Thu Sep 1 12:17:52 EDT 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@@ -489,23 +489,23 @@
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:
- 32 bytes: each row header (approximate)
+ 28 bytes: each row header (approximate)
24 bytes: one int field and one text field
+ 4 bytes: pointer on page to tuple
----------------------------------------
- 60 bytes per row
+ 56 bytes per row
The data page size in PostgreSQL is 8192 bytes (8 KB), so:
8192 bytes per page
- ------------------- = 136 rows per database page (rounded down)
- 60 bytes per row
+ ------------------- = 146 rows per database page (rounded down)
+ 56 bytes per row
100000 data rows
- -------------------- = 735 database pages (rounded up)
- 128 rows per page
+ -------------------- = 685 database pages (rounded up)
+ 146 rows per page
-735 database pages * 8192 bytes per page = 6,021,120 bytes (6 MB)
+685 database pages * 8192 bytes per page = 5,611,520 bytes (5.6 MB)
Indexes do not require as much overhead, but do contain the data that
is being indexed, so they can be large also.
diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html
index 2d46904eb32..d1e8af9f1e0 100644
--- a/doc/src/FAQ/FAQ.html
+++ b/doc/src/FAQ/FAQ.html
@@ -10,7 +10,7 @@
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Thu Aug 11 09:21:58 EDT 2005</P>
+ <P>Last updated: Thu Sep 1 12:17:52 EDT 2005</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)
@@ -635,23 +635,23 @@ table?</TD><TD>unlimited</TD></TR>
The size of the PostgreSQL database file containing this data can
be estimated as 6.4 MB:</P>
<PRE>
- 32 bytes: each row header (approximate)
+ 28 bytes: each row header (approximate)
24 bytes: one int field and one text field
+ 4 bytes: pointer on page to tuple
----------------------------------------
- 60 bytes per row
+ 56 bytes per row
The data page size in PostgreSQL is 8192 bytes (8 KB), so:
8192 bytes per page
- ------------------- = 136 rows per database page (rounded down)
- 60 bytes per row
+ ------------------- = 146 rows per database page (rounded down)
+ 56 bytes per row
100000 data rows
- -------------------- = 735 database pages (rounded up)
- 128 rows per page
+ -------------------- = 685 database pages (rounded up)
+ 146 rows per page
-735 database pages * 8192 bytes per page = 6,021,120 bytes (6 MB)
+685 database pages * 8192 bytes per page = 5,611,520 bytes (5.6 MB)
</PRE>
<P>Indexes do not require as much overhead, but do contain the data
--
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