diff --git a/doc/FAQ b/doc/FAQ
index 55c229725f08d53106488881fc1b82221225260e..20a03f9b152adea120c5a3bd9e56640a7f1c451a 100644
--- a/doc/FAQ
+++ b/doc/FAQ
@@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Tue Feb 12 12:18:09 EST 2002
+ Last updated: Thu Feb 14 12:14:47 EST 2002
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@@ -48,13 +48,11 @@
Why?
3.4) When I try to start postmaster, I get IpcSemaphoreCreate errors.
Why?
- 3.5) How do I prevent other hosts from accessing my PostgreSQL
- database?
- 3.6) Why can't I connect to my database from another machine?
- 3.7) How do I tune the database engine for better performance?
- 3.8) What debugging features are available?
- 3.9) Why do I get "Sorry, too many clients" when trying to connect?
- 3.10) What are the pg_sorttempNNN.NN files in my database directory?
+ 3.5) How do I control connections from other hosts?
+ 3.6) How do I tune the database engine for better performance?
+ 3.7) What debugging features are available?
+ 3.8) Why do I get "Sorry, too many clients" when trying to connect?
+ 3.9) What are the pg_sorttempNNN.NN files in my database directory?
Operational Questions
@@ -484,7 +482,7 @@
Administrator's Guide for more detailed information about shared
memory and semaphores.
- 3.5) How do I prevent other hosts from accessing my PostgreSQL database?
+ 3.5) How do I control connections from other hosts?
By default, PostgreSQL only allows connections from the local machine
using Unix domain sockets. Other machines will not be able to connect
@@ -492,14 +490,7 @@
authentication by modifying the file $PGDATA/pg_hba.conf accordingly.
This will allow TCP/IP connections.
- 3.6) Why can't I connect to my database from another machine?
-
- The default configuration allows only Unix domain socket connections
- from the local machine. To enable TCP/IP connections, make sure
- postmaster has been started with the -i option, and add an appropriate
- host entry to the file pgsql/data/pg_hba.conf.
-
- 3.7) How do I tune the database engine for better performance?
+ 3.6) How do I tune the database engine for better performance?
Certainly, indexes can speed up queries. The EXPLAIN command allows
you to see how PostgreSQL is interpreting your query, and which
@@ -530,7 +521,7 @@
You can also use the CLUSTER command to group data in tables to match
an index. See the CLUSTER manual page for more details.
- 3.8) What debugging features are available?
+ 3.7) What debugging features are available?
PostgreSQL has several features that report status information that
can be valuable for debugging purposes.
@@ -577,7 +568,7 @@
pgsql/data/base/dbname directory. The client profile file will be put
in the client's current directory.
- 3.9) Why do I get "Sorry, too many clients" when trying to connect?
+ 3.8) Why do I get "Sorry, too many clients" when trying to connect?
You need to increase postmaster's limit on how many concurrent backend
processes it can start.
@@ -601,7 +592,7 @@
was 64, and changing it required a rebuild after altering the
MaxBackendId constant in include/storage/sinvaladt.h.
- 3.10) What are the pg_sorttempNNN.NN files in my database directory?
+ 3.9) What are the pg_sorttempNNN.NN files in my database directory?
They are temporary files generated by the query executor. For example,
if a sort needs to be done to satisfy an ORDER BY, and the sort
@@ -671,29 +662,31 @@
4.6) How much database disk space is required to store data from a typical
text file?
- A PostgreSQL database may need six-and-a-half times the disk space
- required to store the data in a flat file.
-
- Consider a file of 300,000 lines with two integers on each line. The
- flat file is 2.4 MB. The size of the PostgreSQL database file
- containing this data can be estimated at 14 MB:
+ A PostgreSQL database may require up to five times the disk space to
+ store data from a text file.
+
+ 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
+ of the PostgreSQL database file containing this data can be estimated
+ as 6.6 MB:
36 bytes: each row header (approximate)
- + 8 bytes: two int fields @ 4 bytes each
+ 26 bytes: two int fields @ 4 bytes each
+ 4 bytes: pointer on page to tuple
----------------------------------------
- 48 bytes per row
+ 66 bytes per row
The data page size in PostgreSQL is 8192 bytes (8 KB), so:
8192 bytes per page
- ------------------- = 171 rows per database page (rounded up)
- 48 bytes per row
+ ------------------- = 124 rows per database page (rounded down)
+ 66 bytes per row
- 300000 data rows
- -------------------- = 1755 database pages
- 171 rows per page
+ 100000 data rows
+ -------------------- = 807 database pages (rounded up)
+ 124 rows per page
-1755 database pages * 8192 bytes per page = 14,376,960 bytes (14 MB)
+807 database pages * 8192 bytes per page = 6,610,944 bytes (6.6 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 40ad62917a7f4b4e287b1866a70cbb33ec2a1b10..9ad2d5089c231e9606aaeb58264db7eefdecb0d7 100644
--- a/doc/src/FAQ/FAQ.html
+++ b/doc/src/FAQ/FAQ.html
@@ -14,7 +14,7 @@
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Tue Feb 12 12:18:09 EST 2002</P>
+ <P>Last updated: Thu Feb 14 12:14:47 EST 2002</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
@@ -72,16 +72,13 @@
get <I>IpcMemoryCreate</I> errors. Why?<BR>
<A href="#3.4">3.4</A>) When I try to start <I>postmaster</I>, I
get <I>IpcSemaphoreCreate</I> errors. Why?<BR>
- <A href="#3.5">3.5</A>) How do I prevent other hosts from
- accessing my PostgreSQL database?<BR>
- <A href="#3.6">3.6</A>) Why can't I connect to my database from
- another machine?<BR>
- <A href="#3.7">3.7</A>) How do I tune the database engine for
+ <A href="#3.5">3.5</A>) How do I control connections from other hosts?<BR>
+ <A href="#3.6">3.6</A>) How do I tune the database engine for
better performance?<BR>
- <A href="#3.8">3.8</A>) What debugging features are available?<BR>
- <A href="#3.9">3.9</A>) Why do I get <I>"Sorry, too many
+ <A href="#3.7">3.7</A>) What debugging features are available?<BR>
+ <A href="#3.8">3.8</A>) Why do I get <I>"Sorry, too many
clients"</I> when trying to connect?<BR>
- <A href="#3.10">3.10</A>) What are the <I>pg_sorttempNNN.NN</I>
+ <A href="#3.9">3.9</A>) What are the <I>pg_sorttempNNN.NN</I>
files in my database directory?<BR>
@@ -633,8 +630,8 @@
PostgreSQL Administrator's Guide for more detailed information
about shared memory and semaphores.</P>
- <H4><A name="3.5">3.5</A>) How do I prevent other hosts from
- accessing my PostgreSQL database?</H4>
+ <H4><A name="3.5">3.5</A>) How do I control connections from other
+ hosts?</H4>
<P>By default, PostgreSQL only allows connections from the local
machine using Unix domain sockets. Other machines will not be able
@@ -643,16 +640,7 @@
<I>$PGDATA/pg_hba.conf</I> accordingly. This will allow TCP/IP
connections.</P>
- <H4><A name="3.6">3.6</A>) Why can't I connect to my database from
- another machine?</H4>
-
- <P>The default configuration allows only Unix domain socket
- connections from the local machine. To enable TCP/IP connections,
- make sure <I>postmaster</I> has been started with the <I>-i</I>
- option, and add an appropriate host entry to the file
- <I>pgsql/data/pg_hba.conf</I>.</P>
-
- <H4><A name="3.7">3.7</A>) How do I tune the database engine for
+ <H4><A name="3.6">3.6</A>) How do I tune the database engine for
better performance?</H4>
<P>Certainly, indexes can speed up queries. The
@@ -689,7 +677,7 @@
data in tables to match an index. See the <SMALL>CLUSTER</SMALL>
manual page for more details.</P>
- <H4><A name="3.8">3.8</A>) What debugging features are
+ <H4><A name="3.7">3.7</A>) What debugging features are
available?</H4>
<P>PostgreSQL has several features that report status information
@@ -745,7 +733,7 @@
in the <I>pgsql/data/base/dbname</I> directory. The client profile
file will be put in the client's current directory.</P>
- <H4><A name="3.9">3.9</A>) Why do I get <I>"Sorry, too many
+ <H4><A name="3.8">3.8</A>) Why do I get <I>"Sorry, too many
clients"</I> when trying to connect?</H4>
<P>You need to increase <I>postmaster</I>'s limit on how many
@@ -775,7 +763,7 @@
the MaxBackendId constant in
<I>include/storage/sinvaladt.h</I>.</P>
- <H4><A name="3.10">3.10</A>) What are the <I>pg_sorttempNNN.NN</I>
+ <H4><A name="3.9">3.9</A>) What are the <I>pg_sorttempNNN.NN</I>
files in my database directory?</H4>
<P>They are temporary files generated by the query executor. For
@@ -862,30 +850,32 @@
<H4><A name="4.6">4.6</A>) How much database disk space is required
to store data from a typical text file?</H4>
- <P>A PostgreSQL database may need six-and-a-half times the disk
- space required to store the data in a flat file.</P>
+ <P>A PostgreSQL database may require up to five times the disk space
+ to store data from a text file.</P>
- <P>Consider a file of 300,000 lines with two integers on each line.
- The flat file is 2.4 MB. The size of the PostgreSQL database file
- containing this data can be estimated at 14 MB:</P>
+ <P>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
+ of the PostgreSQL database file containing this data can be
+ estimated as 6.6 MB:</P>
<PRE>
36 bytes: each row header (approximate)
- + 8 bytes: two int fields @ 4 bytes each
+ 26 bytes: two int fields @ 4 bytes each
+ 4 bytes: pointer on page to tuple
----------------------------------------
- 48 bytes per row
+ 66 bytes per row
The data page size in PostgreSQL is 8192 bytes (8 KB), so:
8192 bytes per page
- ------------------- = 171 rows per database page (rounded up)
- 48 bytes per row
+ ------------------- = 124 rows per database page (rounded down)
+ 66 bytes per row
- 300000 data rows
- -------------------- = 1755 database pages
- 171 rows per page
+ 100000 data rows
+ -------------------- = 807 database pages (rounded up)
+ 124 rows per page
-1755 database pages * 8192 bytes per page = 14,376,960 bytes (14 MB)
+807 database pages * 8192 bytes per page = 6,610,944 bytes (6.6 MB)
</PRE>
<P>Indexes do not require as much overhead, but do contain the data