Update FAQ.

doc/FAQ

 
                 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.

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