Update FAQ.

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.
+   A PostgreSQL database may require up to five times the disk space to
+   store data from a text 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:
+   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.