Add reference pages for utilities and remove standalone chapters for same.
- (last updated 1999-04-08 )
+ (last updated 1999-05-19 )
-
PostgreSQL is copyright (
C ) 1998-9
+
PostgreSQL is copyright (
© ) 1998-9
by the Postgres Global Development Group.
&ports;
&config;
+ &layout;
&install;
&installw;
&runtime;
&security;
- &options;
&start-ag;
+ &trouble;
&recovery;
®ress;
&release;
--- /dev/null
+
+
System Layout
+
+
+
<ProductName>Postgres</ProductName> file layout
+
+
+
+
+shows how the
Postgres distribution is laid
+ out when installed in the default way. For simplicity,
+ we will assume that
Postgres + has been installed in the
+ directory /usr/local/pgsql . Therefore, wherever
+ you see the directory /usr/local/pgsql you should
+ substitute the name of the directory where
+ actually installed.
+ All
Postgres commands are installed
+ in the directory
+ /usr/local/pgsql/bin . Therefore, you should add
+ this directory to your shell command path. If you use
+ a variant of the Berkeley C shell, such as csh or tcsh,
+ you would add
+set path = ( /usr/local/pgsql/bin path )
+
+ in the .login file in your home directory. If you use
+ a variant of the Bourne shell, such as sh, ksh, or
+ bash, then you would add
+PATH=/usr/local/pgsql/bin:$PATH
+export PATH
+
+ to the .profile file in your home directory.
+ From now on, we will assume that you have added the
+
Postgres bin directory to your path.
+ In addition, we
+ will make frequent reference to "setting a shell
+ variable" or "setting an environment variable" throughout
+ this document. If you did not fully understand the
+ last paragraph on modifying your search path, you
+ should consult the UNIX manual pages that describe your
+ shell before going any further.
+
+
+If you have not set things up in the
+default way, you may have some more work to do.
+For example, if the database server machine is a remote machine, you
+will need to set the PGHOST environment variable to the name
+of the database server machine. The environment variable
+PGPORT may also have to be set. The bottom line is this: if
+you try to start an application program and it complains
+that it cannot connect to the
postmaster ,
+you must go back and make sure that your
+environment is properly set up.
+
+
+
+
+
-
-
-Massimo
-Dal Zotto
-
-
-Transcribed 1998-10-16
-
-
-Using </span>pg_options
-
-
-Contributed by
Massimo Dal Zotto -
-
-
-The optional file data/pg_options contains runtime
-options used by the backend to control trace messages and other backend
-tunable parameters.
-What makes this file interesting is the fact that it is re-read by a backend
-when it receives a SIGHUP signal, making thus possible to change run-time
-options on the fly without needing to restart
-The options specified in this file may be debugging flags used by the trace
-package (backend/utils/misc/trace.c ) or numeric
-parameters which can be used by the backend to control its behaviour.
-New options and parameters must be defined in
-backend/utils/misc/trace.c and
-backend/include/utils/trace.h .
-
-For example suppose we want to add conditional trace messages and a tunable
-numeric parameter to the code in file foo.c .
-All we need to do is to add the constant TRACE_FOO and OPT_FOO_PARAM into
-backend/include/utils/trace.h :
-
+
+
+ Massimo
+ Dal Zotto
+
+
+ Transcribed 1998-10-16
+
+
+ </span>pg_options
+
+
+
Contributed by
Massimo Dal Zotto +
+
+
+ The optional file data/pg_options contains runtime
+ options used by the backend to control trace messages and other backend
+ tunable parameters.
+ What makes this file interesting is the fact that it is re-read by a backend
+ when it receives a SIGHUP signal, making thus possible to change run-time
+ options on the fly without needing to restart
+ The options specified in this file may be debugging flags used by the trace
+ package (backend/utils/misc/trace.c ) or numeric
+ parameters which can be used by the backend to control its behaviour.
+ New options and parameters must be defined in
+ backend/utils/misc/trace.c and
+ backend/include/utils/trace.h .
+
+ For example suppose we want to add conditional trace messages and a tunable
+ numeric parameter to the code in file foo.c .
+ All we need to do is to add the constant TRACE_FOO and OPT_FOO_PARAM into
+ backend/include/utils/trace.h :
+
/* file trace.h */
enum pg_option_enum {
...
NUM_PG_OPTIONS /* must be the last item of enum */
};
-
+
-and a corresponding line in backend/utils/misc/trace.c :
+ and a corresponding line in backend/utils/misc/trace.c :
/* file trace.c */
static char *opt_names[] = {
...
"foo", /* trace foo functions */
"fooparam" /* foo tunable parameter */
};
-
+
-Options in the two files must be specified in exactly the same order.
-In the foo source files we can now reference the new flags with:
+ Options in the two files must be specified in exactly the same order.
+ In the foo source files we can now reference the new flags with:
/* file foo.c */
#include "trace.h"
#define foo_param pg_options[OPT_FOO_PARAM]
do_more_foo(x, y);
}
}
-
-
-Existing files using private trace flags can be changed by simply adding
-the following code:
+
+
+ Existing files using private trace flags can be changed by simply adding
+ the following code:
#include "trace.h"
/* int my_own_flag = 0; -- removed */
#define my_own_flag pg_options[OPT_MY_OWN_FLAG]
-
-
-All pg_options are initialized to zero at backend startup. If we need a
-different default value we must add some initialization code at the beginning
-of PostgresMain .
+
+
+ All pg_options are initialized to zero at backend startup. If we need a
+ different default value we must add some initialization code at the beginning
+ of PostgresMain .
-Now we can set the foo_param and enable foo trace by writing values into the
-data/pg_options file:
+ Now we can set the foo_param and enable foo trace by writing values into the
+ data/pg_options file:
# file pg_options
...
foo=1
fooparam=17
-
-
-The new options will be read by all new backends when they are started.
-To make effective the changes for all running backends we need to send a
-SIGHUP to the postmaster. The signal will be automatically sent to all the
-backends. We can also activate the changes only for a specific backend by
-sending the SIGHUP directly to it.
-
-pg_options can also be specified with the -T switch of
-
+
+
+ The new options will be read by all new backends when they are started.
+ To make effective the changes for all running backends we need to send a
+ SIGHUP to the postmaster. The signal will be automatically sent to all the
+ backends. We can also activate the changes only for a specific backend by
+ sending the SIGHUP directly to it.
+
+ pg_options can also be specified with the -T switch of
+
postgres options -T "verbose=2,query,hostlookup-"
-
-
-The functions used for printing errors and debug messages can now make use
-of the syslog(2) facility. Message printed to stdout
-or stderr are prefixed by a timestamp containing also the backend pid:
-
+
+
+ The functions used for printing errors and debug messages can now make use
+ of the syslog(2) facility. Message printed to stdout
+ or stderr are prefixed by a timestamp containing also the backend pid:
+
#timestamp #pid #message
980127.17:52:14.173 [29271] StartTransactionCommand
980127.17:52:14.174 [29271] ProcessUtility: drop table t;
980127.19:52:14.292 [29286] Async_NotifyFrontEnd
980127.19:52:14.413 [29286] Async_NotifyFrontEnd done
980127.19:52:14.466 [29286] Async_NotifyHandler done
-
-
-This format improves readability of the logs and allows people to understand
-exactly which backend is doing what and at which time. It also makes
-easier to write simple awk or perl scripts which monitor the log to
-detect database errors or problem, or to compute transaction time statistics.
-
-Messages printed to syslog use the log facility LOG_LOCAL0.
-The use of syslog can be controlled with the syslog pg_option.
-Unfortunately many functions call directly printf()
-to print their messages to stdout or stderr and this output can't be
-redirected to syslog or have timestamps in it.
-It would be advisable that all calls to printf would be replaced with the
-PRINTF macro and output to stderr be changed to use EPRINTF instead so that
-we can control all output in a uniform way.
-
-
-The new pg_options mechanism is more convenient than defining new backend
-option switches because:
-
-
-
-we don't have to define a different switch for each thing we want to control.
-All options are defined as keywords in an external file stored in the data
-directory.
-
-
-
-
-we don't have to restart
Postgres to change
- the setting of some option.
-Normally backend options are specified to the postmaster and passed to each
-backend when it is started. Now they are read from a file.
-
-
-
-
-we can change options on the fly while a backend is running. We can thus
-investigate some problem by activating debug messages only when the problem
-appears. We can also try different values for tunable parameters.
-
-
-
-
-The format of the pg_options file is as follows:
-
+
+
+ This format improves readability of the logs and allows people to understand
+ exactly which backend is doing what and at which time. It also makes
+ easier to write simple awk or perl scripts which monitor the log to
+ detect database errors or problem, or to compute transaction time statistics.
+
+ Messages printed to syslog use the log facility LOG_LOCAL0.
+ The use of syslog can be controlled with the syslog pg_option.
+ Unfortunately many functions call directly printf()
+ to print their messages to stdout or stderr and this output can't be
+ redirected to syslog or have timestamps in it.
+ It would be advisable that all calls to printf would be replaced with the
+ PRINTF macro and output to stderr be changed to use EPRINTF instead so that
+ we can control all output in a uniform way.
+
+
+ The new pg_options mechanism is more convenient than defining new backend
+ option switches because:
+
+
+
+ we don't have to define a different switch for each thing we want to control.
+ All options are defined as keywords in an external file stored in the data
+ directory.
+
+
+
+
+
we don't have to restart
Postgres to change
+ the setting of some option.
+ Normally backend options are specified to the postmaster and passed to each
+ backend when it is started. Now they are read from a file.
+
+
+
+
+ we can change options on the fly while a backend is running. We can thus
+ investigate some problem by activating debug messages only when the problem
+ appears. We can also try different values for tunable parameters.
+
+
+
+
+ The format of the pg_options file is as follows:
+
# comment
option =integer_value # set value for option
option # set option = 1
option + # set option = 1
option - # set option = 0
-
-
-Note that keyword can also be
-an abbreviation of the option name defined in
-backend/utils/misc/trace.c .
-
-
-The options currently defined in
-backend/utils/misc/trace.c are the following:
-
-
-
-
-all
-
-
-Global trace flag. Allowed values are:
-
-
-
-
-
-0
-
-
-Trace messages enabled individually
-
-
-
-
-
-
-1
-
-
-Enable all trace messages
-
-
-
-
-
-
--1
-
-
-Disable all trace messages
-
-
-
-
-
-
-
-
-
-
-verbose
-
-
-Verbosity flag. Allowed values are:
-
-
-
-
-
-0
-
-
-No messages. This is the default.
-
-
-
-
-
-
-1
-
-
-Print information messages.
-
-
-
-
-
-
-2
-
-
-Print more information messages.
-
-
-
-
-
-
-
-
-
-
-query
-
-
-Query trace flag. Allowed values are:
-
-
-
-
-
-0
-
-
-Don't print query.
-
-
-
-
-
-
-1
-
-
-Print a condensed query in one line.
-
-
-
-
-
-
-4
-
-
-Print the full query.
-
-
-
-
-
-
-
-
-
-
-plan
-
-
-Print query plan.
-
-
-
-
-
-
-parse
-
-
-Print parser output.
-
-
-
-
-
-
-rewritten
-
-
-Print rewritten query.
-
-
-
-
-
-
-parserstats
-
-
-Print parser statistics.
-
-
-
-
-
-
-plannerstats
-
-
-Print planner statistics.
-
-
-
-
-
-
-executorstats
-
-
-Print executor statistics.
-
-
-
-
-
-
-shortlocks
-
-
-Currently unused but needed to enable features in the future.
-
-
-
-
-
-
-locks
-
-
-Trace locks.
-
-
-
-
-
-
-userlocks
-
-
-Trace user locks.
-
-
-
-
-
-
-spinlocks
-
-
-Trace spin locks.
-
-
-
-
-
-
-notify
-
-
-Trace notify functions.
-
-
-
-
-
-
-malloc
-
-
-Currently unused.
-
-
-
-
-
-
-palloc
-
-
-Currently unused.
-
-
-
-
-
-
-lock_debug_oidmin
-
-
-Minimum relation oid traced by locks.
-
-
-
-
-
-
-lock_debug_relid
-
-
-oid, if not zero, of relation traced by locks.
-
-
-
-
-
-
-lock_read_priority
-
-
-Currently unused.
-
-
-
-
-
-
-deadlock_timeout
-
-
-Deadlock check timer.
-
-
-
-
-
-
-syslog
-
-
-syslog flag. Allowed values are:
-
-
-
-
-
-0
-
-
-Messages to stdout/stderr.
-
-
-
-
-
-
-1
-
-
-Messages to stdout/stderr and syslog.
-
-
-
-
-
-
-2
-
-
-Messages only to syslog.
-
-
-
-
-
-
-
-
-
-
-hostlookup
-
-
-Enable hostname lookup in ps_status.
-
-
-
-
-
-
-showportnumber
-
-
-Show port number in ps_status.
-
-
-
-
-
-
-notifyunlock
-
-
-Unlock of pg_listener after notify.
-
-
-
-
-
-
-notifyhack
-
-
-Remove duplicate tuples from pg_listener.
-
-
-
-
-
-
-For example my pg_options file contains the following values:
-
-verbose=2
-query
-hostlookup
-showportnumber
-
-
-
-
-
-Some of the existing code using private variables and option switches has
-been changed to make use of the pg_options feature, mainly in
-postgres.c . It would be advisable to modify
-all existing code
-in this way, so that we can get rid of many of the switches on
-the
Postgres command line
-and can have more tunable options
-with a unique place to put option values.
-
-
-
+
+
+ Note that keyword can also be
+ an abbreviation of the option name defined in
+ backend/utils/misc/trace.c .
+
+
+ Refer to The Administrator's Guide chapter
+ on runtime options for a complete list of currently supported
+ options.
+
+
+ Some of the existing code using private variables and option switches has
+ been changed to make use of the pg_options feature, mainly in
+ postgres.c . It would be advisable to modify
+ all existing code
+ in this way, so that we can get rid of many of the switches on
+ the
Postgres command line
+ and can have more tunable options
+ with a unique place to put option values.
+
+
+
+
+
+++ /dev/null
-
-
<Command>pgaccess</Command>
-
-This section needs to be written. Volunteers?
-
-
-
- (last updated 1998-02-23 )
+ (last updated 1998-05-19 )
- &sql;
- &environ;
- &manage;
- &syntax;
+ &sql;
+ &syntax;
&datatype;
&oper;
&func;
&typeconv;
- &keys;
+ &keys;
&array;
&inherit;
- &query-ug;
+ &environ;
+ &manage;
&storage;
- &psql;
- &pgaccess;
&commands;
&installw;
&runtime;
&security;
- &options;
&start-ag;
&recovery;
®ress;
&arch-dev;
+ &options;
&geqo;
&protocol;
&signals;
+
-
PostgreSQL Programmer's Guide
-
- Covering v6.4 for general release
-
- The PostgreSQL Development Team
-
+
PostgreSQL Programmer's Guide
+
+ Covering v6.5
+
+ The PostgreSQL Development Team
+
-
- Thomas
- Lockhart
- Caltech/JPL
-
-
+
+ Thomas
+ Lockhart
+ Caltech/JPL
+
+
-->
- (last updated 1998-10-27 )
-
+ (last updated 1999-05-19
+
-
-
PostgreSQL is copyright (C) 1998
-by the Postgres Global Development Group.
-
-
+
+
PostgreSQL is copyright (©) 1998-9
+ by the Postgres Global Development Group.
+
+
-
+
-
Summary
-
- developed originally in the UC Berkeley Computer Science Department,
- pioneered many of the object-relational concepts
- now becoming available in some commercial databases.
-It provides SQL92/SQL3 language support,
- transaction integrity, and type extensibility.
-
PostgreSQL is a public-domain,
- open source descendant of this original Berkeley code.
-
-
-
-&intro-pg;
-&arch-pg;
-&extend;
-&xfunc;
-&xtypes;
-&xoper;
-&xaggr;
-&rules;
-&xindex;
-&gist;
-&xplang;
-&dfunc;
+
Summary
+
+ developed originally in the UC Berkeley Computer Science Department,
+ pioneered many of the object-relational concepts
+ now becoming available in some commercial databases.
+ It provides SQL92/SQL3 language support,
+ transaction integrity, and type extensibility.
+
PostgreSQL is a public-domain,
+ open source descendant of this original Berkeley code.
+
+
+
+ &intro-pg;
+ &arch-pg;
+ &extend;
+ &xfunc;
+ &xtypes;
+ &xoper;
+ &xaggr;
+ &rules;
+ &xindex;
+ &gist;
+ &xplang;
+ &dfunc;
&func-ref;
-->
-&trigger;
-&spi;
-&lobj;
-&libpq;
-&libpqpp;
-&libpgtcl;
-&ecpg;
-&odbc;
-&jdbc;
-
+ &trigger;
+ &spi;
+ &lobj;
+ &libpq;
+ &libpqpp;
+ &libpgtcl;
+ &ecpg;
+ &odbc;
+ &jdbc;
+
-
-&arch-dev;
-&geqo;
-&protocol;
-&signals;
-&compiler;
-&bki;
-&page;
+
+ &arch-dev;
+ &options;
+ &geqo;
+ &protocol;
+ &signals;
+ &compiler;
+ &bki;
+ &page;
-&docguide;
+ &docguide;
-&biblio;
+ &biblio;
[MELT93] and [DATE97].
- You should be aware that some language features
-
are not part of the
ANSI standard.
-
-
-
-
Interactive Monitor
-
- In the examples that follow, we assume that you have
- created the mydb database as described in the previous
-
subsection and have started
psql .
- Examples in this manual can also be found in
- /usr/local/pgsql/src/tutorial/ . Refer to the
- README file in that directory for how to use them. To
- start the tutorial, do the following:
-
+ You should be aware that some language features
+
are extensions to the
ANSI standard.
+
+
+
+
Interactive Monitor
+
+ In the examples that follow, we assume that you have
+ created the mydb database as described in the previous
+ subsection and have started
psql .
+ Examples in this manual can also be found in
+ /usr/local/pgsql/src/tutorial/ . Refer to the
+ README file in that directory for how to use them. To
+ start the tutorial, do the following:
+
% cd /usr/local/pgsql/src/tutorial
% psql -s mydb
Welcome to the POSTGRESQL interactive sql monitor:
You are currently connected to the database: postgres
mydb=> \i basics.sql
-
-
-
- The \i command read in queries from the specified
- files. The -s option puts you in single step mode which
- pauses before sending a query to the backend. Queries
- in this section are in the file basics.sql .
-
-
-has a variety of \d commands for showing system information.
-Consult these commands for more details;
-for a listing, type
\? at the
psql prompt.
-
-
-
-
-
Concepts
-
- The fundamental notion in
Postgres is that of a class,
- which is a named collection of object instances. Each
- instance has the same collection of named attributes,
- and each attribute is of a specific type. Furthermore,
- each instance has a permanent
object identifier (
OID )
- that is unique throughout the installation. Because
-
SQL syntax refers to tables, we will use the terms
- table and class interchangeably.
- Likewise, an
SQL row is an
-
instance and
SQL columns - are attributes .
- As previously discussed, classes are grouped into
- databases, and a collection of databases managed by a
- single
postmaster process constitutes an installation
- or site.
-
-
-
-
-
Creating a New Class
-
- You can create a new class by specifying the class
- name, along with all attribute names and their types:
-
+
+
+
+ The \i command read in queries from the specified
+ files. The -s option puts you in single step mode which
+ pauses before sending a query to the backend. Queries
+ in this section are in the file basics.sql .
+
+
+ has a variety of \d commands for showing system information.
+ Consult these commands for more details;
+ for a listing, type
\? at the
psql prompt.
+
+
+
+
+
Concepts
+
+ The fundamental notion in
Postgres is that of a class,
+ which is a named collection of object instances. Each
+ instance has the same collection of named attributes,
+ and each attribute is of a specific type. Furthermore,
+ each instance has a permanent object identifier
+ that is unique throughout the installation. Because
+
SQL syntax refers to tables, we will use the terms
+ table and class interchangeably.
+ Likewise, an
SQL row is an
+
instance and
SQL columns + are attributes .
+ As previously discussed, classes are grouped into
+ databases, and a collection of databases managed by a
+ single
postmaster process constitutes an installation
+ or site.
+
+
+
+
+
Creating a New Class
+
+ You can create a new class by specifying the class
+ name, along with all attribute names and their types:
+
CREATE TABLE weather (
city varchar(80),
temp_lo int, -- low temperature
prcp real, -- precipitation
date date
);
-
-
-
- Note that both keywords and identifiers are case-insensitive; identifiers can become
-case-sensitive by surrounding them with double-quotes as allowed by
SQL92 .
-
Postgres SQL supports the usual
- float , real , smallint , char(N) ,
- varchar(N) , date , time ,
-and timestamp , as well as other types of general utility and
-a rich set of geometric types. As we will
- see later,
Postgres can be customized with an
- arbitrary number of
- user-defined data types. Consequently, type names are
- not syntactical keywords, except where required to support special cases in the
SQL92 standard.
- So far, the
Postgres create command looks exactly like
- the command used to create a table in a traditional
- relational system. However, we will presently see that
- classes have properties that are extensions of the
- relational model.
-
-
-
-
-
Populating a Class with Instances
-
- The insert statement is used to populate a class with
- instances:
-
+
+
+
+ Note that both keywords and identifiers are case-insensitive; identifiers can become
+ case-sensitive by surrounding them with double-quotes as allowed
+
Postgres SQL supports the usual
+ float , real , smallint , char(N) ,
+ varchar(N) , date , time ,
+ and timestamp , as well as other types of general utility and
+ a rich set of geometric types. As we will
+ see later,
Postgres can be customized with an
+ arbitrary number of
+ user-defined data types. Consequently, type names are
+ not syntactical keywords, except where required to support special
+ cases in the
SQL92 standard.
+ So far, the
Postgres create command
+ looks exactly like
+ the command used to create a table in a traditional
+ relational system. However, we will presently see that
+ classes have properties that are extensions of the
+ relational model.
+
+
+
+
+
Populating a Class with Instances
+
+ The insert statement is used to populate a class with
+ instances:
+
INSERT INTO weather
VALUES ('San Francisco', 46, 50, 0.25, '11/27/1994')
-
-
-
- You can also use the copy command to perform load large
- amounts of data from flat (
ASCII ) files.
-
-
-
-
-
Querying a Class
-
- The weather class can be queried with normal relational
- selection and projection queries. A
SQL select - statement is used to do this. The statement is divided into
- a target list (the part that lists the attributes to be
- returned) and a qualification (the part that specifies
- any restrictions). For example, to retrieve all the
- rows of weather, type:
+
+
+
+ You can also use the copy command to perform load large
+ amounts of data from flat (
ASCII ) files.
+ This is usually faster because the data is read (or written) as a single atomic
+ transaction directly to or from the target table. An example would be:
+
+COPY INTO weather FROM '/home/user/weather.txt'
+ USING DELIMITERS '|';
+
+
+ where the path name for the source file must be available to the backend server
+ machine, not the client, since the backend server reads the file directly.
+
+
+
+
+
+
+
+
Querying a Class
+
+ The weather class can be queried with normal relational
+ selection and projection queries. A
SQL select + statement is used to do this. The statement is divided into
+ a target list (the part that lists the attributes to be
+ returned) and a qualification (the part that specifies
+ any restrictions). For example, to retrieve all the
+ rows of weather, type:
SELECT * FROM WEATHER;
-
+
- and the output should be:
+ and the output should be:
+--------------+---------+---------+------+------------+
|city | temp_lo | temp_hi | prcp | date |
+--------------+---------+---------+------+------------+
+--------------+---------+---------+------+------------+
|Hayward | 37 | 54 | | 11-29-1994 |
+--------------+---------+---------+------+------------+
-
- You may specify any arbitrary expressions in the target list. For example, you can do:
+
+ You may specify any arbitrary expressions in the target list. For example, you can do:
SELECT city, (temp_hi+temp_lo)/2 AS temp_avg, date FROM weather;
-
-
+
+
- Arbitrary Boolean operators
- (and , or and not ) are
- allowed in the qualification of any query. For example,
+ Arbitrary Boolean operators
+ (and , or and not ) are
+ allowed in the qualification of any query. For example,
SELECT * FROM weather
WHERE city = 'San Francisco'
AND prcp > 0.0;
-
+
+results in:
+--------------+---------+---------+------+------------+
|city | temp_lo | temp_hi | prcp | date |
+--------------+---------+---------+------+------------+
|San Francisco | 46 | 50 | 0.25 | 11-27-1994 |
+--------------+---------+---------+------+------------+
-
-
+
+
- As a final note, you can specify that the results of a
- select can be returned in a sorted order
- or with duplicate instances removed.
+ As a final note, you can specify that the results of a
+ select can be returned in a sorted order
+ or with duplicate instances removed.
SELECT DISTINCT city
FROM weather
ORDER BY city;
-
-
-
+
+
+
-
-
Redirecting SELECT Queries
+
+
Redirecting SELECT Queries
- Any select query can be redirected to a new class
+ Any select query can be redirected to a new class
SELECT * INTO TABLE temp FROM weather;
-
-
-
- This forms an implicit create command, creating a new
- class temp with the attribute names and types specified
- in the target list of the select into command. We can
- then, of course, perform any operations on the resulting
- class that we can perform on other classes.
-
-
-
-
-
Joins Between Classes
-
- Thus far, our queries have only accessed one class at a
- time. Queries can access multiple classes at once, or
- access the same class in such a way that multiple
- instances of the class are being processed at the same
- time. A query that accesses multiple instances of the
- same or different classes at one time is called a join
- query.
- As an example, say we wish to find all the records that
- are in the temperature range of other records. In
- effect, we need to compare the temp_lo and temp_hi
- attributes of each EMP instance to the temp_lo and
- temp_hi attributes of all other EMP instances.
-
-This is only a conceptual model. The actual join may
- be performed in a more efficient manner, but this is invisible to the user.
-
-
-
- We can do this with the following query:
-
+
+
+
+ This forms an implicit create command, creating a new
+ class temp with the attribute names and types specified
+ in the target list of the select into command. We can
+ then, of course, perform any operations on the resulting
+ class that we can perform on other classes.
+
+
+
+
+
Joins Between Classes
+
+ Thus far, our queries have only accessed one class at a
+ time. Queries can access multiple classes at once, or
+ access the same class in such a way that multiple
+ instances of the class are being processed at the same
+ time. A query that accesses multiple instances of the
+ same or different classes at one time is called a join
+ query.
+ As an example, say we wish to find all the records that
+ are in the temperature range of other records. In
+ effect, we need to compare the temp_lo and temp_hi
+ attributes of each EMP instance to the temp_lo and
+ temp_hi attributes of all other EMP instances.
+
+ This is only a conceptual model. The actual join may
+ be performed in a more efficient manner, but this is invisible to the user.
+
+
+
+ We can do this with the following query:
+
SELECT W1.city, W1.temp_lo AS low, W1.temp_hi AS high,
W2.city, W2.temp_lo AS low, W2.temp_hi AS high
FROM weather W1, weather W2
+--------------+-----+------+---------------+-----+------+
|San Francisco | 37 | 54 | San Francisco | 46 | 50 |
+--------------+-----+------+---------------+-----+------+
-
-
-
-The semantics of such a join are
- that the qualification
- is a truth expression defined for the Cartesian product of
- the classes indicated in the query. For those instances in
- the Cartesian product for which the qualification is true,
-
Postgres computes and returns the values specified in the
- target list.
Postgres SQL does not assign any meaning to
- duplicate values in such expressions. This means that
Postgres - sometimes recomputes the same target list several times;
- this frequently happens when Boolean expressions are connected
- with an "or". To remove such duplicates, you must use
- the select distinct statement.
-
-
-
-
- In this case, both W1 and W2 are surrogates for an
- instance of the class weather, and both range over all
- instances of the class. (In the terminology of most
- database systems, W1 and W2 are known as range variables .)
- A query can contain an arbitrary number of
- class names and surrogates.
-
-
-
-
-
Updates
-
- You can update existing instances using the update command.
- Suppose you discover the temperature readings are
- all off by 2 degrees as of Nov 28, you may update the
- data as follow:
-
+
+
+
+ The semantics of such a join are
+ that the qualification
+ is a truth expression defined for the Cartesian product of
+ the classes indicated in the query. For those instances in
+ the Cartesian product for which the qualification is true,
+
Postgres computes and returns the
+ values specified in the target list.
+ does not assign any meaning to
+ duplicate values in such expressions.
+ This means that
Postgres + sometimes recomputes the same target list several times;
+ this frequently happens when Boolean expressions are connected
+ with an "or". To remove such duplicates, you must use
+ the select distinct statement.
+
+
+
+
+ In this case, both W1 and W2 are surrogates for an
+ instance of the class weather, and both range over all
+ instances of the class. (In the terminology of most
+ database systems, W1 and W2 are known as range variables .)
+ A query can contain an arbitrary number of
+ class names and surrogates.
+
+
+
+
+
Updates
+
+ You can update existing instances using the update command.
+ Suppose you discover the temperature readings are
+ all off by 2 degrees as of Nov 28, you may update the
+ data as follow:
+
UPDATE weather
SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
WHERE date > '11/28/1994';
-
-
-
+
+
+
-
-
Deletions
+
+
Deletions
- Deletions are performed using the delete command:
+ Deletions are performed using the delete command:
DELETE FROM weather WHERE city = 'Hayward';
-
+
- All weather recording belongs to Hayward is removed.
- One should be wary of queries of the form
+ All weather recording belongs to Hayward is removed.
+ One should be wary of queries of the form
DELETE FROM classname;
-
-
- Without a qualification, delete will simply
- remove all instances of the given class, leaving it
- empty. The system will not request confirmation before
- doing this.
-
-
-
-
-
Using Aggregate Functions
-
- Like most other query languages,
PostgreSQL supports
- aggregate functions.
-The current implementation of
Postgres aggregate functions have some limitations.
- Specifically, while there are aggregates to compute
- such functions as the count , sum ,
- avg (average), max (maximum) and
- min (minimum) over a set of instances, aggregates can only
- appear in the target list of a query and not directly in the
- qualification (the where clause). As an example,
-
+
+
+ Without a qualification, delete will simply
+ remove all instances of the given class, leaving it
+ empty. The system will not request confirmation before
+ doing this.
+
+
+
+
+
Using Aggregate Functions
+
+ Like most other query languages,
+ aggregate functions.
+ The current implementation of
+
Postgres aggregate functions have some limitations.
+ Specifically, while there are aggregates to compute
+ such functions as the count , sum ,
+ avg (average), max (maximum) and
+ min (minimum) over a set of instances, aggregates can only
+ appear in the target list of a query and not directly in the
+ qualification (the where clause). As an example,
+
SELECT max(temp_lo) FROM weather;
-
+
-is allowed, while
+ is allowed, while
SELECT city FROM weather WHERE temp_lo = max(temp_lo);
-
+
-is not. However, as is often the case the query can be restated to accomplish
-the intended result; here by using a subselect :
+ is not. However, as is often the case the query can be restated to accomplish
+ the intended result; here by using a subselect :
SELECT city FROM weather WHERE temp_lo = (SELECT max(temp_lo) FROM weather);
-
-
+
+
- Aggregates may also have group by clauses:
+ Aggregates may also have group by clauses:
SELECT city, max(temp_lo)
FROM weather
GROUP BY city;
-
-
-
-
+
+
+
+
+
+
-
-
Runtime Environment
-
-This chapter outlines the interaction between
Postgres and
-the operating system.
-
-
-
Using <Productname>Postgres</Productname> from Unix
-
-All
Postgres commands that are executed
-directly from a Unix shell are
-found in the directory .../bin
. Including this directory in
-your search path will make executing the commands easier.
-
-A collection of system catalogs exist at each site. These include a
-class (pg_user ) that contains an instance for each valid
-
Postgres user. The instance specifies a set of
-
Postgres privileges, such as
-the ability to act as
Postgres super-user,
- the ability to create/destroy
-databases, and the ability to update the system catalogs. A Unix
-user cannot do anything with
Postgres -until an appropriate instance is
-installed in this class. Further information on the system catalogs
-is available by running queries on the appropriate classes.
-
-
-
-
-
-
System Layout
-
-
-
<ProductName>Postgres</ProductName> file layout
-
-
-
-
-shows how the
Postgres distribution is laid
- out when installed in the default way. For simplicity,
- we will assume that
Postgres - has been installed in the
- directory /usr/local/pgsql . Therefore, wherever
- you see the directory /usr/local/pgsql you should
- substitute the name of the directory where
- actually installed.
- All
Postgres commands are installed
- in the directory
- /usr/local/pgsql/bin . Therefore, you should add
- this directory to your shell command path. If you use
- a variant of the Berkeley C shell, such as csh or tcsh,
- you would add
-set path = ( /usr/local/pgsql/bin path )
-
- in the .login file in your home directory. If you use
- a variant of the Bourne shell, such as sh, ksh, or
- bash, then you would add
-PATH=/usr/local/pgsql/bin:$PATH
-export PATH
-
- to the .profile file in your home directory.
- From now on, we will assume that you have added the
-
Postgres bin directory to your path.
- In addition, we
- will make frequent reference to "setting a shell
- variable" or "setting an environment variable" throughout
- this document. If you did not fully understand the
- last paragraph on modifying your search path, you
- should consult the UNIX manual pages that describe your
- shell before going any further.
-
-
-If you have not set things up in the
-default way, you may have some more work to do.
-For example, if the database server machine is a remote machine, you
-will need to set the PGHOST environment variable to the name
-of the database server machine. The environment variable
-PGPORT may also have to be set. The bottom line is this: if
-you try to start an application program and it complains
-that it cannot connect to the
postmaster ,
-you must go back and make sure that your
-environment is properly set up.
-
+
+
Runtime Environment
+
+ This chapter outlines the interaction between
Postgres and
+ the operating system.
+
+
+
+
Using <Productname>Postgres</Productname> from Unix
+
+ All
Postgres commands that are executed
+ directly from a Unix shell are
+ found in the directory .../bin
. Including this directory in
+ your search path will make executing the commands easier.
+
+
+ A collection of system catalogs exist at each site. These include a
+ class (pg_user ) that contains an instance for each valid
+
Postgres user. The instance specifies a set of
+
Postgres privileges, such as
+ the ability to act as
Postgres super-user,
+ the ability to create/destroy
+ databases, and the ability to update the system catalogs. A Unix
+ user cannot do anything with
Postgres + until an appropriate instance is
+ installed in this class. Further information on the system catalogs
+ is available by running queries on the appropriate classes.
+
+
+
+
+
Starting <Application>postmaster</Application>
+
+ Nothing can happen to a database unless the
+ process is running. As the site administrator, there
+ are a number of things you should remember before
+ starting the
postmaster .
+ These are discussed in the installation and configuration sections
+ of this manual.
+ However, if
Postgres has been installed by following
+ the installation instructions exactly as written, the
+ following simple command is all you should
+ need to start the
postmaster :
+
+% postmaster
+
+
+
+ The
postmaster occasionally prints out
+ messages which
+ are often helpful during troubleshooting. If you wish
+ to view debugging messages from the
postmaster ,
+ you can
+ start it with the -d option and redirect the output to
+ the log file:
+
+% postmaster -d >& pm.log &
+
+
+ If you do not wish to see these messages, you can type
+% postmaster -S
+
+ and the
postmaster will be "S"ilent.
+ Notice that there
+ is no ampersand ("&") at the end of the last example so
+ postmaster will be running in the foreground.
+
+
+
+
+ Using pg_options
+
+
+ Contributed by
Massimo Dal Zotto +
+
+
+ The optional file data/pg_options contains runtime
+ options used by the backend to control trace messages and other backend
+ tunable parameters.
+ The file is re-read by a backend
+ when it receives a SIGHUP signal, making thus possible to change run-time
+ options on the fly without needing to restart
+ The options specified in this file may be debugging flags used by the trace
+ package (backend/utils/misc/trace.c ) or numeric
+ parameters which can be used by the backend to control its behaviour.
+
+
+ All pg_options are initialized to zero at backend startup.
+ New or modified options will be read by all new backends when they are started.
+ To make effective any changes for all running backends we need to send a
+ SIGHUP to the postmaster. The signal will be automatically sent to all the
+ backends. We can also activate the changes only for a specific backend by
+ sending the SIGHUP directly to it.
+
+ pg_options can also be specified with the -T switch of
+
+postgres options -T "verbose=2,query,hostlookup-"
+
+
+
+ The functions used for printing errors and debug messages can now make use
+ of the syslog(2) facility. Message printed to stdout
+ or stderr are prefixed by a timestamp containing also the backend pid:
+
+#timestamp #pid #message
+980127.17:52:14.173 [29271] StartTransactionCommand
+980127.17:52:14.174 [29271] ProcessUtility: drop table t;
+980127.17:52:14.186 [29271] SIIncNumEntries: table is 70% full
+980127.17:52:14.186 [29286] Async_NotifyHandler
+980127.17:52:14.186 [29286] Waking up sleeping backend process
+980127.19:52:14.292 [29286] Async_NotifyFrontEnd
+980127.19:52:14.413 [29286] Async_NotifyFrontEnd done
+980127.19:52:14.466 [29286] Async_NotifyHandler done
+
+
+ This format improves readability of the logs and allows people to understand
+ exactly which backend is doing what and at which time. It also makes
+ easier to write simple awk or perl scripts which monitor the log to
+ detect database errors or problem, or to compute transaction time statistics.
+
+ Messages printed to syslog use the log facility LOG_LOCAL0.
+ The use of syslog can be controlled with the syslog pg_option.
+ Unfortunately many functions call directly printf()
+ to print their messages to stdout or stderr and this output can't be
+ redirected to syslog or have timestamps in it.
+ It would be advisable that all calls to printf would be replaced with the
+ PRINTF macro and output to stderr be changed to use EPRINTF instead so that
+ we can control all output in a uniform way.
+
+
+ The format of the pg_options file is as follows:
+
+# comment
+option =integer_value # set value for option
+option # set option = 1
+option + # set option = 1
+option - # set option = 0
+
+
+ Note that keyword can also be
+ an abbreviation of the option name defined in
+ backend/utils/misc/trace.c .
+
+
+
pg_options File
+
+ For example my pg_options file contains the following values:
+
+verbose=2
+query
+hostlookup
+showportnumber
+
+
+
+
+
+
+
Recognized Options
+
+ The options currently defined are:
+
+
+
+
+ all
+
+
+ Global trace flag. Allowed values are:
+
+
+
+
+
+ 0
+
+
+ Trace messages enabled individually
+
+
+
+
+
+
+ 1
+
+
+ Enable all trace messages
+
+
+
+
+
+
+ -1
+
+
+ Disable all trace messages
+
+
+
+
+
+
+
+
+
+
+ verbose
+
+
+ Verbosity flag. Allowed values are:
+
+
+
+
+
+ 0
+
+
+ No messages. This is the default.
+
+
+
+
+
+
+ 1
+
+
+ Print information messages.
+
+
+
+
+
+
+ 2
+
+
+ Print more information messages.
+
+
+
+
+
+
+
+
+
+
+ query
+
+
+ Query trace flag. Allowed values are:
+
+
+
+
+
+ 0
+
+
+ Don't print query.
+
+
+
+
+
+
+ 1
+
+
+ Print a condensed query in one line.
+
+
+
+
+
+
+ 4
+
+
+ Print the full query.
+
+
+
+
+
+
+
+
+
+
+ plan
+
+
+ Print query plan.
+
+
+
+
+
+
+ parse
+
+
+ Print parser output.
+
+
+
+
+
+
+ rewritten
+
+
+ Print rewritten query.
+
+
+
+
+
+
+ parserstats
+
+
+ Print parser statistics.
+
+
+
+
+
+
+ plannerstats
+
+
+ Print planner statistics.
+
+
+
+
+
+
+ executorstats
+
+
+ Print executor statistics.
+
+
+
+
+
+
+ shortlocks
+
+
+ Currently unused but needed to enable features in the future.
+
+
+
+
+
+
+ locks
+
+
+ Trace locks.
+
+
+
+
+
+
+ userlocks
+
+
+ Trace user locks.
+
+
+
+
+
+
+ spinlocks
+
+
+ Trace spin locks.
+
+
+
+
+
+
+ notify
+
+
+ Trace notify functions.
+
+
+
+
+
+
+ malloc
+
+
+ Currently unused.
+
+
+
+
+
+
+ palloc
+
+
+ Currently unused.
+
+
+
+
+
+
+ lock_debug_oidmin
+
+
+ Minimum relation oid traced by locks.
+
+
+
+
+
+
+ lock_debug_relid
+
+
+ oid, if not zero, of relation traced by locks.
+
+
+
+
+
+
+ lock_read_priority
+
+
+ Currently unused.
+
+
+
+
+
+
+ deadlock_timeout
+
+
+ Deadlock check timer.
+
+
+
+
+
+
+ syslog
+
+
+ syslog flag. Allowed values are:
+
+
+
+
+
+ 0
+
+
+ Messages to stdout/stderr.
+
+
+
+
+
+
+ 1
+
+
+ Messages to stdout/stderr and syslog.
+
+
+
+
+
+
+ 2
+
+
+ Messages only to syslog.
+
+
+
+
+
+
+
+
+
+
+ hostlookup
+
+
+ Enable hostname lookup in ps_status.
+
+
+
+
+
+
+ showportnumber
+
+
+ Show port number in ps_status.
+
+
+
+
+
+
+ notifyunlock
+
+
+ Unlock of pg_listener after notify.
+
+
+
+
+
+
+ notifyhack
+
+
+ Remove duplicate tuples from pg_listener.
+
+
+
+
+
+
+
+
+
+
two exceptions: manual system catalog updates are not permitted if the
user does not have pg_user.usecatupd set, and destruction of
system catalogs (or modification of their schemas) is never allowed.
+
+
+
for each attribute
- 1 ≤ i &le ; k ,
+ 1 <&equal; i <&equal ; k ,
where the values of the attributes are taken from. We often write
a relation scheme as
integers. We define this by assigning a data type to each
attribute. The type of SNAME will be
VARCHAR(20) (this is the
SQL type
- for character strings of length ≤ 20), the type of SNO will be
+ for character strings of length <&equal; 20),
+ the type of SNO will be
INTEGER . With the assignment of a data type we also have selected
a domain for an attribute. The domain of SNAME is the set of all
- character strings of length ≤ 20, the domain of SNO is the set of
+ character strings of length <&equal; 20,
+ the domain of SNO is the set of
all integer numbers.
Model
- In section
+ In
we defined the mathematical notion of
the relational model. Now we know how the data can be stored using a
relational data model but we do not know what to do with all these
projecting out the duplicate column.
- Let's have a look at the tables that are produced by evaluating the steps
- necessary for a join.
- Let the following two tables be given:
+
+
An Inner Join
+ Let's have a look at the tables that are produced by evaluating the steps
+ necessary for a join.
+ Let the following two tables be given:
+
R A | B | C S C | D | E
---+---+--- ---+---+---
1 | 2 | 3 3 | a | b
4 | 5 | 6 6 | c | d
7 | 8 | 9
-
-
+
+
+
First we calculate the Cartesian product
- - thomas 1998-02-24
-->
-
-
Starting <Application>postmaster</Application>
-
- Nothing can happen to a database unless the
- process is running. As the site administrator, there
- are a number of things you should remember before
- starting the
postmaster .
-These are discussed in the installation and configuration sections
-of this manual.
- However, if
Postgres has been installed by following
- the installation instructions exactly as written, the
- following simple command is all you should
- need to start the
postmaster :
-% postmaster
-
- The
postmaster occasionally prints out
-messages which
- are often helpful during troubleshooting. If you wish
- to view debugging messages from the
postmaster ,
-you can
- start it with the -d option and redirect the output to
- the log file:
-% postmaster -d >& pm.log &
-
- If you do not wish to see these messages, you can type
-% postmaster -S
-
- and the
postmaster will be "S"ilent.
-Notice that there
- is no ampersand ("&") at the end of the last example.
-
-
-
-
-
Adding and Deleting Users
-
-
createuser enables specific users to access
-
destroyuser removes users and
- prevents them from accessing
Postgres .
-Note that these
- commands only affect users with respect to
- they have no effect on users other privileges or status with regards
-to the underlying
- operating system.
-
-
-
-
-
Disk Management
-
-
-
-
-
Alternate Locations
-
-It is possible to create a database in a location other than the default
-location for the installation. Remember that all database access actually
-occurs through the database backend, so that any location specified must
-be accessible by the backend.
-
- Alternate database locations are created and referenced by an environment variable
- which gives the absolute path to the intended storage location.
-This environment variable must have been defined before the backend was started
-and must be writable by the postgres administrator account.
-Any valid environment variable name may be used to reference an alternate
-location, although using variable name with a prefix of PGDATA is recommended
-to avoid confusion and conflict with other variables.
-
-
- In previous versions of
Postgres ,
-it was also permissable to use an absolute path name to specify an alternate storage location.
-The environment variable style of specification
-is to be preferred since it allows the site administrator more flexibility in
-managing disk storage.
-If you prefer using absolute paths, you may do so by defining
-"ALLOW_ABSOLUTE_DBPATHS" and recompiling
Postgres - To do this, either add this line
+
+
Adding and Deleting Users
+
+
createuser enables specific users to access
+
destroyuser removes users and
+ prevents them from accessing
Postgres .
+ Note that these
+ commands only affect users with respect to
+ they have no effect on users other privileges or status with regards
+ to the underlying
+ operating system.
+
+
+
+
+
Disk Management
+
+
+
Alternate Locations
+
+ It is possible to create a database in a location other than the default
+ location for the installation. Remember that all database access actually
+ occurs through the database backend, so that any location specified must
+ be accessible by the backend.
+
+
+ Alternate database locations are created and referenced by an environment variable
+ which gives the absolute path to the intended storage location.
+ This environment variable must have been defined before the backend was started
+ and must be writable by the postgres administrator account.
+ Any valid environment variable name may be used to reference an alternate
+ location, although using variable name with a prefix of PGDATA is recommended
+ to avoid confusion and conflict with other variables.
+
+
+
+ In previous versions of
Postgres ,
+ it was also permissable to use an absolute path name
+ to specify an alternate storage location.
+ The environment variable style of specification
+ is to be preferred since it allows the site administrator more flexibility in
+ managing disk storage.
+ If you prefer using absolute paths, you may do so by defining
+ "ALLOW_ABSOLUTE_DBPATHS" and recompiling
Postgres + To do this, either add this line
+
#define ALLOW_ABSOLUTE_DBPATHS 1
-
-to the file src/include/config.h , or by specifying
+
+
+ to the file src/include/config.h , or by specifying
+
CFLAGS+= -DALLOW_ABSOLUTE_DBPATHS
-
-in your Makefile.custom .
-
-
-
-Remember that database creation is actually performed by the database backend.
-Therefore, any environment variable specifying an alternate location must have
-been defined before the backend was started. To define an alternate location
-PGDATA2 pointing to /home/postgres/data , first type
+
+
+ in your Makefile.custom .
+
+
+
+ Remember that database creation is actually performed by the database backend.
+ Therefore, any environment variable specifying an alternate location must have
+ been defined before the backend was started. To define an alternate location
+ PGDATA2 pointing to /home/postgres/data , first type
+
% setenv PGDATA2 /home/postgres/data
-
-to define the environment variable to be used with subsequent commands.
-Usually, you will want to define this variable in the
-.profile
-or
-.cshrc
-initialization file to ensure that it is defined upon system startup.
-Any environment variable can be used to reference alternate location,
-although it is preferred that the variables be prefixed with "PGDATA"
-to eliminate confusion and the possibility of conflicting with or
-overwriting other variables.
-
-To create a data storage area in PGDATA2, ensure
-that /home/postgres already exists and is writable
-by the postgres administrator.
-Then from the command line, type
+
+
+ to define the environment variable to be used with subsequent commands.
+ Usually, you will want to define this variable in the
+ .profile
+ or
+ .cshrc
+ initialization file to ensure that it is defined upon system startup.
+ Any environment variable can be used to reference alternate location,
+ although it is preferred that the variables be prefixed with "PGDATA"
+ to eliminate confusion and the possibility of conflicting with or
+ overwriting other variables.
+
+
+ To create a data storage area in PGDATA2, ensure
+ that /home/postgres already exists and is writable
+ by the postgres administrator.
+ Then from the command line, type
+
% setenv PGDATA2 /home/postgres/data
% initlocation $PGDATA2
Creating Postgres database system directory /home/postgres/data
Creating Postgres database system directory /home/postgres/data/base
-
-
-To test the new location, create a database test by typing
+
+
+
+ To test the new location, create a database test by typing
+
% createdb -D PGDATA2 test
% destroydb test
-
-
-
-
-
-
-
Troubleshooting
-
- Assuming that your site administrator has properly
- started the
postmaster process
-and authorized you to use the database, you (as a user) may begin to start up
- applications. As previously mentioned, you should add
- /usr/local/pgsql/bin to your shell search path.
- In most cases, this is all you should have to do in
- terms of preparation.
-
- If you get the following error message from a
- command (such as
psql or
-connectDB() failed: Is the postmaster running at 'localhost' on port '5432'?
-
- it is usually because either the
postmaster is not running,
- or you are attempting to connect to the wrong server host.
- If you get the following error message:
-FATAL 1:Feb 17 23:19:55:process userid (2360) != database owner (268)
-
- it means that the site administrator started the
postmaster - as the wrong user. Tell him to restart it as
- the
Postgres superuser.
-
-
-
-
-
Managing a Database
-
- Now that
Postgres is up and running we can create
- some databases to experiment with. Here, we describe the
- basic commands for managing a database.
-
-
-
-
Creating a Database
-
- Let's say you want to create a database named mydb.
- You can do this with the following command:
+
+
+
+
+
+
+
+
Managing a Database
+
+ Now that
Postgres is up and running we can create
+ some databases to experiment with. Here, we describe the
+ basic commands for managing a database.
+
+
+
+
Creating a Database
+
+ Let's say you want to create a database named mydb.
+ You can do this with the following command:
+
% createdb mydb
-
-
-
Postgres allows you to create
-any number of databases
- at a given site and you automatically become the
- database administrator of the database you just created.
-Database names must have an alphabetic first
- character and are limited to 16 characters in length.
- Not every user has authorization to become a database
- administrator. If
Postgres -refuses to create databases
- for you, then the site administrator needs to grant you
- permission to create databases. Consult your site
- administrator if this occurs.
-
-
-
-
-
Accessing a Database
-
- Once you have constructed a database, you can access it
- by:
-
-
-
-running the
Postgres terminal monitor program
-(
psql ) which allows you to interactively
- enter, edit, and execute
SQL commands.
-
-
-
- writing a C program using the libpq subroutine
- library. This allows you to submit
SQL commands
- from C and get answers and status messages back to
- your program. This interface is discussed further
- in the PostgreSQL Programmer's Guide .
-
-
-
-
- You might want to start up
psql ,
-to try out the examples in this manual. It can be activated for the mydb
- database by typing the command:
+
+
+
Postgres allows you to create
+ any number of databases
+ at a given site and you automatically become the
+ database administrator of the database you just created.
+ Database names must have an alphabetic first
+ character and are limited to 16 characters in length.
+ Not every user has authorization to become a database
+ administrator. If
Postgres + refuses to create databases
+ for you, then the site administrator needs to grant you
+ permission to create databases. Consult your site
+ administrator if this occurs.
+
+
+
+
+
Accessing a Database
+
+ Once you have constructed a database, you can access it
+ by:
+
+
+
+ running the
Postgres terminal monitor program
+ (
psql ) which allows you to interactively
+ enter, edit, and execute
SQL commands.
+
+
+
+ writing a C program using the libpq subroutine
+ library. This allows you to submit
SQL commands
+ from C and get answers and status messages back to
+ your program. This interface is discussed further
+ in the PostgreSQL Programmer's Guide .
+
+
+
+
+ You might want to start up
psql ,
+ to try out the examples in this manual. It can be activated for the mydb
+ database by typing the command:
+
% psql mydb
-
+
- You will be greeted with the following message:
+ You will be greeted with the following message:
Welcome to the Postgres interactive sql monitor:
type \? for help on slash commands
You are currently connected to the database: mydb
mydb=>
-
-
-
-This prompt indicates that the terminal monitor is listening
-to you and that you can type
SQL queries into a
- workspace maintained by the terminal monitor.
- The
psql program responds to escape
- codes that begin
- with the backslash character, "\". For example, you
- can get help on the syntax of various
-
Postgres SQL commands by typing:
+
+
+
+ This prompt indicates that the terminal monitor is listening
+ to you and that you can type
SQL queries into a
+ workspace maintained by the terminal monitor.
+ The
psql program responds to escape
+ codes that begin
+ with the backslash character, "\". For example, you
+ can get help on the syntax of various
+
Postgres SQL commands by typing:
+
mydb=> \h
-
+
- Once you have finished entering your queries into the
- workspace, you can pass the contents of the workspace
- to the
Postgres server by typing:
+ Once you have finished entering your queries into the
+ workspace, you can pass the contents of the workspace
+ to the
Postgres server by typing:
+
mydb=> \g
-
-
- This tells the server to process the query. If you
- terminate your query with a semicolon, the backslash-g is not
- necessary.
psql will automatically
-process semicolon terminated queries.
- To read queries from a file, say myFile, instead of
- entering them interactively, type:
+
+
+ This tells the server to process the query. If you
+ terminate your query with a semicolon, the backslash-g is not
+ necessary.
psql will automatically
+ process semicolon terminated queries.
+ To read queries from a file, say myFile, instead of
+ entering them interactively, type:
+
mydb=> \i fileName
-
+
+
+ To get out of
psql and return to UNIX, type
- To get out of
psql and return to UNIX, type
mydb=> \q
-
-
- and
psql will quit and return
-you to your command
- shell. (For more escape codes, type backslash-h at the monitor
- prompt.)
- White space (i.e., spaces, tabs and newlines) may be
- used freely in
SQL queries.
-Single-line comments are denoted by
- --
. Everything after the dashes up to the end of the
- line is ignored. Multiple-line comments, and comments within a line,
- are denoted by /* ... */
-
-
+
+
+ and
psql will quit and return
+ you to your command
+ shell. (For more escape codes, type backslash-h at the monitor
+ prompt.)
+ White space (i.e., spaces, tabs and newlines) may be
+ used freely in
SQL queries.
+ Single-line comments are denoted by two dashes
+ (--
). Everything after the dashes up to the end of the
+ line is ignored. Multiple-line comments, and comments within a line,
+ are denoted by /* ... */
, a convention borrowed
+
+
-
-
Destroying a Database
+
+
Destroying a Database
- If you are the database administrator for the database
- mydb, you can destroy it using the following UNIX command:
+ If you are the database administrator for the database
+ mydb, you can destroy it using the following UNIX command:
+
% destroydb mydb
-
- This action physically removes all of the UNIX files
- associated with the database and cannot be undone, so
- this should only be done with a great deal of forethought.
-
-
-
-
+
+
+ This action physically removes all of the UNIX files
+ associated with the database and cannot be undone, so
+ this should only be done with a great deal of forethought.
+
+
+
+
+
+
--- /dev/null
+
+
Troubleshooting
+
+
+
Client Connections
+ If you get the following error message from a
+ command (such as
psql or
+
+connectDB() failed: Is the postmaster running at 'localhost' on port '5432'?
+
+
+ it is usually because either the
postmaster is not running,
+ or you are attempting to connect to the wrong server host.
+ If you get the following error message:
+
+FATAL 1:Feb 17 23:19:55:process userid (2360) != database owner (268)
+
+
+ it means that the site administrator started the
postmaster + as the wrong user. Tell him to restart it as
+ the
Postgres superuser.
+
+
+
+
+
Debugging Messages
+
+ The
postmaster occasionally prints out
+ messages which
+ are often helpful during troubleshooting. If you wish
+ to view debugging messages from the
postmaster ,
+ you can
+ start it with the -d option and redirect the output to
+ the log file:
+
+% postmaster -d >& pm.log &
+
+
+ If you do not wish to see these messages, you can type
+% postmaster -S
+
+ and the
postmaster will be "S"ilent.
+ Notice that there
+ is no ampersand ("&") at the end of the last example so
+ postmaster will be running in the foreground.
+
+
+
+
pg_options
+
+
+ Contributed by
Massimo Dal Zotto +
+
+
+ The optional file data/pg_options contains runtime
+ options used by the backend to control trace messages and other backend
+ tunable parameters.
+ What makes this file interesting is the fact that it is re-read by a backend
+ when it receives a SIGHUP signal, making thus possible to change run-time
+ options on the fly without needing to restart
+ The options specified in this file may be debugging flags used by the trace
+ package (backend/utils/misc/trace.c ) or numeric
+ parameters which can be used by the backend to control its behaviour.
+ New options and parameters must be defined in
+ backend/utils/misc/trace.c and
+ backend/include/utils/trace.h .
+
+
+ pg_options can also be specified with the -T switch of
+
+postgres options -T "verbose=2,query,hostlookup-"
+
+
+
+ The functions used for printing errors and debug messages can now make use
+ of the syslog(2) facility. Message printed to stdout
+ or stderr are prefixed by a timestamp containing also the backend pid:
+
+#timestamp #pid #message
+980127.17:52:14.173 [29271] StartTransactionCommand
+980127.17:52:14.174 [29271] ProcessUtility: drop table t;
+980127.17:52:14.186 [29271] SIIncNumEntries: table is 70% full
+980127.17:52:14.186 [29286] Async_NotifyHandler
+980127.17:52:14.186 [29286] Waking up sleeping backend process
+980127.19:52:14.292 [29286] Async_NotifyFrontEnd
+980127.19:52:14.413 [29286] Async_NotifyFrontEnd done
+980127.19:52:14.466 [29286] Async_NotifyHandler done
+
+
+
+ This format improves readability of the logs and allows people to understand
+ exactly which backend is doing what and at which time. It also makes
+ easier to write simple awk or perl scripts which monitor the log to
+ detect database errors or problem, or to compute transaction time statistics.
+
+
+ Messages printed to syslog use the log facility LOG_LOCAL0.
+ The use of syslog can be controlled with the syslog pg_option.
+ Unfortunately many functions call directly printf()
+ to print their messages to stdout or stderr and this output can't be
+ redirected to syslog or have timestamps in it.
+ It would be advisable that all calls to printf would be replaced with the
+ PRINTF macro and output to stderr be changed to use EPRINTF instead so that
+ we can control all output in a uniform way.
+
+
+ The format of the pg_options file is as follows:
+
+# comment
+option =integer_value # set value for option
+option # set option = 1
+option + # set option = 1
+option - # set option = 0
+
+
+ Note that keyword can also be
+ an abbreviation of the option name defined in
+ backend/utils/misc/trace.c .
+
+
+ Refer to
+ for a complete list of option keywords and possible values.
+
+
+
+
+
+
-
PostgreSQL Tutorial
-
- Covering v6.3 for general release
-
- The PostgreSQL Development Team
-
+
PostgreSQL Tutorial
+
+ Covering v6.5
+
+ The PostgreSQL Development Team
+
-
- Thomas
- Lockhart
- Caltech/JPL
-
-
+
+ Thomas
+ Lockhart
+ Caltech/JPL
+
+
-->
- (last updated 1998-02-23 )
-
+ (last updated 1999-05-19
+
-
-
PostgreSQL is copyright (C) 1998 by the Postgres Global Development Group.
-
-
+
+
PostgreSQL is copyright (©) 1998-9
+ by the Postgres Global Development Group.
+
+
-
+
-
Summary
-
- developed originally in the UC Berkeley Computer Science Department,
- pioneered many of the object-relational concepts
- now becoming available in some commercial databases.
-It provides SQL92/SQL3 language support,
- transaction integrity, and type extensibility.
-
PostgreSQL is a public-domain, open source descendant
- of this original Berkeley code.
-
-
-
-&intro;
-&arch;
-&start;
-&query;
-&advanced;
-
-&biblio;
+
Summary
+
+ developed originally in the UC Berkeley Computer Science Department,
+ pioneered many of the object-relational concepts
+ now becoming available in some commercial databases.
+ It provides SQL92/SQL3 language support,
+ transaction integrity, and type extensibility.
+
PostgreSQL is a public-domain, open source descendant
+ of this original Berkeley code.
+
+
+
+ &intro;
+ &arch;
+ &start;
+ &query;
+ &advanced;
+
+ &biblio;
+
+
-
PostgreSQL User's Guide
-
- Covering v6.4 for general release
-
- The PostgreSQL Development Team
-
+
PostgreSQL User's Guide
+
+ Covering v6.5
+
+ The PostgreSQL Development Team
+
-
- Thomas
- Lockhart
- Caltech/JPL
-
-
+
+ Thomas
+ Lockhart
+ Caltech/JPL
+
+
- (last updated 1998-02-23 )
-
+ (last updated 1999-05-19
+
-
-
PostgreSQL is copyright (C) 1998
-by the Postgres Global Development Group.
-
-
+
+
PostgreSQL is copyright (©) 1998-9
+ by the Postgres Global Development Group.
+
+
-
+
-
Summary
-
- developed originally in the UC Berkeley Computer Science Department,
- pioneered many of the object-relational concepts
- now becoming available in some commercial databases.
-It provides SQL92/SQL3 language support,
- transaction integrity, and type extensibility.
-
PostgreSQL is a public-domain, open source descendant
- of this original Berkeley code.
-
-
-
- &intro;
+
Summary
+
+ developed originally in the UC Berkeley Computer Science Department,
+ pioneered many of the object-relational concepts
+ now becoming available in some commercial databases.
+ It provides SQL92/SQL3 language support,
+ transaction integrity, and type extensibility.
+
PostgreSQL is a public-domain, open source descendant
+ of this original Berkeley code.
+
+
+
+ &intro;
&sql;
- &environ;
- &manage;
&syntax;
- &datatype;
- &oper;
- &func;
- &typeconv;
+ &datatype;
+ &oper;
+ &func;
+ &typeconv;
&keys;
- &array;
- &inherit;
- &query-ug;
- &storage;
- &psql;
- &pgaccess;
- &commands;
-
-
+ &array;
+ &inherit;
+ &environ;
+ &manage;
+ &storage;
+ &commands;
+
+
&biblio;
projects / postgresql.git / commitdiff