diff --git a/doc/FAQ b/doc/FAQ
index 3c35b3c2ec6adb04ed7fb84d493bbed7d368f197..128d589f7c5f31f9557c24c91288db7ae8581f7e 100644
--- a/doc/FAQ
+++ b/doc/FAQ
@@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Mon Jan 31 20:41:21 EST 2005
+ Last updated: Mon Jan 31 21:31:39 EST 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@@ -68,19 +68,18 @@
4.11.3) Why aren't my sequence numbers reused on transaction abort?
Why are there gaps in the numbering of my sequence/SERIAL column?
4.12) What is an OID? What is a TID?
- 4.13) What is the meaning of some of the terms used in PostgreSQL?
- 4.14) Why do I get the error "ERROR: Memory exhausted in
+ 4.13) Why do I get the error "ERROR: Memory exhausted in
AllocSetAlloc()"?
- 4.15) How do I tell what PostgreSQL version I am running?
- 4.16) Why does my large-object operations get "invalid large obj
+ 4.14) How do I tell what PostgreSQL version I am running?
+ 4.15) Why does my large-object operations get "invalid large obj
descriptor"?
- 4.17) How do I create a column that will default to the current time?
- 4.18) How do I perform an outer join?
- 4.19) How do I perform queries using multiple databases?
- 4.20) How do I return multiple rows or columns from a function?
- 4.21) Why can't I reliably create/drop temporary tables in PL/PgSQL
+ 4.16) How do I create a column that will default to the current time?
+ 4.17) How do I perform an outer join?
+ 4.18) How do I perform queries using multiple databases?
+ 4.19) How do I return multiple rows or columns from a function?
+ 4.20) Why can't I reliably create/drop temporary tables in PL/PgSQL
functions?
- 4.22) What encryption options are available?
+ 4.21) What encryption options are available?
Extending PostgreSQL
@@ -394,6 +393,7 @@
properly. First, by running configure with the --enable-cassert
option, many assert()s monitor the progress of the backend and halt
the program when something unexpected occurs.
+
The postmaster has a -d option that allows even more detailed
information to be reported. The -d option takes a number that
specifies the debug level. Be warned that high debug level values
@@ -517,14 +517,16 @@
4.4) What is the maximum size for a row, a table, and a database?
These are the limits:
- Maximum size for a database? unlimited (32 TB databases exist)
- Maximum size for a table? 32 TB
- Maximum size for a row? 1.6TB
- Maximum size for a field? 1 GB
- Maximum number of rows in a table? unlimited
- Maximum number of columns in a table? 250-1600 depending on column types
- Maximum number of indexes on a table? unlimited
-
+
+ Maximum size for a database? unlimited (32 TB databases exist)
+ Maximum size for a table? 32 TB
+ Maximum size for a row? 1.6TB
+ Maximum size for a field? 1 GB
+ Maximum number of rows in a table? unlimited
+ Maximum number of columns in a table? 250-1600 depending on column
+ types
+ Maximum number of indexes on a table? unlimited
+
Of course, these are not actually unlimited, but limited to available
disk space and memory/swap space. Performance may suffer when these
values get unusually large.
@@ -611,15 +613,15 @@
* The search string can not start with a character class, e.g.
[a-e].
* Case-insensitive searches such as ILIKE and ~* do not utilize
- indexes. Instead, use functional indexes, which are described in
- section 4.10.
+ indexes. Instead, use expression indexes, which are described in
+ section 4.8.
* The default C locale must be used during initdb because it is not
- possible to know the next-greater character in a non-C locale. You
- can create a special text_pattern_ops index for such cases that
- work only for LIKE indexing.
+ possible to know the next-greatest character in a non-C locale.
+ You can create a special text_pattern_ops index for such cases
+ that work only for LIKE indexing.
In pre-8.0 releases, indexes often can not be used unless the data
- types exactly match the index's column types. This is particularly
+ types exactly match the index's column types. This was particularly
true of int2, int8, and numeric column indexes.
4.7) How do I see how the query optimizer is evaluating my query?
@@ -640,7 +642,7 @@
WHERE lower(col) = 'abc';
This will not use an standard index. However, if you create a
- functional index, it will be used:
+ expresssion index, it will be used:
CREATE INDEX tabindex ON tab (lower(col));
4.9) In a query, how do I detect if a field is NULL?
@@ -649,14 +651,13 @@
4.10) What is the difference between the various character types?
-Type Internal Name Notes
---------------------------------------------------
-VARCHAR(n) varchar size specifies maximum length, no padding
-CHAR(n) bpchar blank padded to the specified fixed length
-TEXT text no specific upper limit on length
-BYTEA bytea variable-length byte array (null-byte safe)
-"char" char one character
-
+ Type Internal Name Notes
+ VARCHAR(n) varchar size specifies maximum length, no padding
+ CHAR(n) bpchar blank padded to the specified fixed length
+ TEXT text no specific upper limit on length
+ BYTEA bytea variable-length byte array (null-byte safe)
+ "char" char one character
+
You will see the internal name when examining system catalogs and in
some error messages.
@@ -692,9 +693,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
);
See the create_sequence manual page for more information about
- sequences. You can also use each row's OID field as a unique value.
- However, if you need to dump and reload the database, you need to use
- pg_dump's -o option or COPY WITH OIDS option to preserve the OIDs.
+ sequences.
4.11.2) How do I get the value of a SERIAL insert?
@@ -716,16 +715,10 @@ BYTEA bytea variable-length byte array (null-byte safe)
execute("INSERT INTO person (name) VALUES ('Blaise Pascal')");
new_id = execute("SELECT currval('person_id_seq')");
- Finally, you could use the OID returned from the INSERT statement to
- look up the default value, though this is probably the least portable
- approach, and the oid value will wrap around when it reaches 4
- billion. In Perl, using DBI with the DBD::Pg module, the oid value is
- made available via $sth->{pg_oid_status} after $sth->execute().
-
4.11.3) Doesn't currval() lead to a race condition with other users?
- No. currval() returns the current value assigned by your backend, not
- by all users.
+ No. currval() returns the current value assigned by your session, not
+ by all sessions.
4.11.4) Why aren't my sequence numbers reused on transaction abort? Why are
there gaps in the numbering of my sequence/SERIAL column?
@@ -751,25 +744,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
values. TIDs change after rows are modified or reloaded. They are used
by index entries to point to physical rows.
- 4.13) What is the meaning of some of the terms used in PostgreSQL?
-
- Some of the source code and older documentation use terms that have
- more common usage. Here are some:
- * table, relation, class
- * row, record, tuple
- * column, field, attribute
- * retrieve, select
- * replace, update
- * append, insert
- * OID, serial value
- * portal, cursor
- * range variable, table name, table alias
-
- A list of general database terms can be found at:
- http://hea-www.harvard.edu/MST/simul/software/docs/pkgs/pgsql/glossary
- /glossary.html
-
- 4.14) Why do I get the error "ERROR: Memory exhausted in AllocSetAlloc()"?
+ 4.13) Why do I get the error "ERROR: Memory exhausted in AllocSetAlloc()"?
You probably have run out of virtual memory on your system, or your
kernel has a low limit for certain resources. Try this before starting
@@ -784,11 +759,11 @@ BYTEA bytea variable-length byte array (null-byte safe)
problem with the SQL client because the backend is returning too much
data, try it before starting the client.
- 4.15) How do I tell what PostgreSQL version I am running?
+ 4.14) How do I tell what PostgreSQL version I am running?
From psql, type SELECT version();
- 4.16) Why does my large-object operations get "invalid large obj
+ 4.15) Why does my large-object operations get "invalid large obj
descriptor"?
You need to put BEGIN WORK and COMMIT around any use of a large object
@@ -803,12 +778,12 @@ BYTEA bytea variable-length byte array (null-byte safe)
If you are using a client interface like ODBC you may need to set
auto-commit off.
- 4.17) How do I create a column that will default to the current time?
+ 4.16) How do I create a column that will default to the current time?
Use CURRENT_TIMESTAMP:
CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP );
- 4.18) How do I perform an outer join?
+ 4.17) How do I perform an outer join?
PostgreSQL supports outer joins using the SQL standard syntax. Here
are two examples:
@@ -838,7 +813,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
ORDER BY col1
- 4.19) How do I perform queries using multiple databases?
+ 4.18) How do I perform queries using multiple databases?
There is no way to query a database other than the current one.
Because PostgreSQL loads database-specific system catalogs, it is
@@ -848,12 +823,12 @@ BYTEA bytea variable-length byte array (null-byte safe)
course, a client can make simultaneous connections to different
databases and merge the results on the client side.
- 4.20) How do I return multiple rows or columns from a function?
+ 4.19) How do I return multiple rows or columns from a function?
In 7.3, you can easily return multiple rows or columns from a
function, http://techdocs.postgresql.org/guides/SetReturningFunctions.
- 4.21) Why can't I reliably create/drop temporary tables in PL/PgSQL
+ 4.20) Why can't I reliably create/drop temporary tables in PL/PgSQL
functions?
PL/PgSQL caches function contents, and an unfortunate side effect is
@@ -864,7 +839,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
table access in PL/PgSQL. This will cause the query to be reparsed
every time.
- 4.22) What encryption options are available?
+ 4.21) What encryption options are available?
* contrib/pgcrypto contains many encryption functions for use in SQL
queries.
diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html
index 71fd85771075d7f2e82deb2911ba675625ba8c43..d5e816926ccaf300e361bc52b0e2b631c5d7ddb1 100644
--- a/doc/src/FAQ/FAQ.html
+++ b/doc/src/FAQ/FAQ.html
@@ -10,7 +10,7 @@
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Mon Jan 31 20:41:21 EST 2005</P>
+ <P>Last updated: Mon Jan 31 21:31:39 EST 2005</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)
@@ -101,24 +101,22 @@
my sequence/SERIAL column?<BR>
<A href="#4.12">4.12</A>) What is an <SMALL>OID</SMALL>? What is a
<SMALL>TID</SMALL>?<BR>
- <A href="#4.13">4.13</A>) What is the meaning of some of the terms
- used in PostgreSQL?<BR>
- <A href="#4.14">4.14</A>) Why do I get the error <I>"ERROR: Memory
+ <A href="#4.12">4.13</A>) Why do I get the error <I>"ERROR: Memory
exhausted in AllocSetAlloc()"</I>?<BR>
- <A href="#4.15">4.15</A>) How do I tell what PostgreSQL version I
+ <A href="#4.14">4.14</A>) How do I tell what PostgreSQL version I
am running?<BR>
- <A href="#4.16">4.16</A>) Why does my large-object operations get
+ <A href="#4.15">4.15</A>) Why does my large-object operations get
<I>"invalid large obj descriptor"</I>?<BR>
- <A href="#4.17">4.17</A>) How do I create a column that will
+ <A href="#4.16">4.16</A>) How do I create a column that will
default to the current time?<BR>
- <A href="#4.18">4.18</A>) How do I perform an outer join?<BR>
- <A href="#4.19">4.19</A>) How do I perform queries using multiple
+ <A href="#4.17">4.17</A>) How do I perform an outer join?<BR>
+ <A href="#4.18">4.18</A>) How do I perform queries using multiple
databases?<BR>
- <A href="#4.20">4.20</A>) How do I return multiple rows or columns
+ <A href="#4.19">4.19</A>) How do I return multiple rows or columns
from a function?<BR>
- <A href="#4.21">4.21</A>) Why can't I reliably create/drop
+ <A href="#4.20">4.20</A>) Why can't I reliably create/drop
temporary tables in PL/PgSQL functions?<BR>
- <A href="#4.22">4.22</A>) What encryption options are available?<BR>
+ <A href="#4.21">4.21</A>) What encryption options are available?<BR>
<H2 align="center">Extending PostgreSQL</H2>
@@ -531,7 +529,7 @@
option, many <I>assert()</I>s monitor the progress of the backend
and halt the program when something unexpected occurs.</P>
- The <I>postmaster</I> has a <I>-d</I> option that allows even more
+ <P>The <I>postmaster</I> has a <I>-d</I> option that allows even more
detailed information to be reported. The <I>-d</I> option takes a
number that specifies the debug level. Be warned that high debug
level values generate large log files.</P>
@@ -567,7 +565,7 @@
<H4><A name="3.5">3.5</A>) Why do I get <I>"Sorry, too many
clients"</I> when trying to connect?</H4>
- You have reached the default limit is 100 database sessions. You
+ <P>You have reached the default limit is 100 database sessions. You
need to increase the <I>postmaster</I>'s limit on how many
concurrent backend processes it can start by changing the
<I>max_connections</I> value in <I>postgresql.conf</I> and
@@ -672,19 +670,25 @@
table, and a database?</H4>
<P>These are the limits:</P>
-<PRE>
- Maximum size for a database? unlimited (32 TB databases exist)
- Maximum size for a table? 32 TB
- Maximum size for a row? 1.6TB
- Maximum size for a field? 1 GB
- Maximum number of rows in a table? unlimited
- Maximum number of columns in a table? 250-1600 depending on column types
- Maximum number of indexes on a table? unlimited
-</PRE>
-
- Of course, these are not actually unlimited, but limited to
+<CENTER>
+<TABLE BORDER=1>
+<TR><TD>Maximum size for a database?</TD><TD>unlimited (32 TB databases
+exist)</TD></TR>
+<TR><TD>Maximum size for a table?</TD><TD>32 TB</TD></TR>
+<TR><TD>Maximum size for a row?</TD><TD>1.6TB</TD></TR>
+<TR><TD>Maximum size for a field?</TD><TD>1 GB</TD></TR>
+<TR><TD>Maximum number of rows in a table?</TD><TD>unlimited</TD></TR>
+<TR><TD>Maximum number of columns in a table?</TD><TD>250-1600 depending
+on column types</TD></TR>
+<TR><TD>Maximum number of indexes on a
+table?</TD><TD>unlimited</TD></TR>
+</TABLE>
+</CENTER>
+<BR>
+
+ <P>Of course, these are not actually unlimited, but limited to
available disk space and memory/swap space. Performance may suffer
- when these values get unusually large.
+ when these values get unusually large.</P>
<P>The maximum table size of 32 TB does not require large file
support from the operating system. Large tables are stored as
@@ -781,10 +785,10 @@
<LI>The search string can not start with a character class,
e.g. [a-e].</LI>
<LI>Case-insensitive searches such as <SMALL>ILIKE</SMALL> and
- <I>~*</I> do not utilize indexes. Instead, use functional
- indexes, which are described in section <a href="#4.10">4.10</a>.</LI>
+ <I>~*</I> do not utilize indexes. Instead, use expression
+ indexes, which are described in section <a href="#4.8">4.8</a>.</LI>
<LI>The default <I>C</I> locale must be used during
- <i>initdb</i> because it is not possible to know the next-greater
+ <i>initdb</i> because it is not possible to know the next-greatest
character in a non-C locale. You can create a special
<CODE>text_pattern_ops</CODE> index for such cases that work only
for <SMALL>LIKE</SMALL> indexing.
@@ -792,7 +796,7 @@
</UL>
<P>In pre-8.0 releases, indexes often can not be used unless the data
- types exactly match the index's column types. This is particularly
+ types exactly match the index's column types. This was particularly
true of int2, int8, and numeric column indexes.</P>
<H4><A name="4.7">4.7</A>) How do I see how the query optimizer is
@@ -818,7 +822,7 @@
</PRE>
This will not use an standard index. However, if you create a
- functional index, it will be used:
+ expresssion index, it will be used:
<PRE>
CREATE INDEX tabindex ON tab (lower(col));
</PRE>
@@ -831,16 +835,20 @@
<H4><A name="4.10">4.10</A>) What is the difference between the
various character types?</H4>
-<PRE>
-Type Internal Name Notes
---------------------------------------------------
-VARCHAR(n) varchar size specifies maximum length, no padding
-CHAR(n) bpchar blank padded to the specified fixed length
-TEXT text no specific upper limit on length
-BYTEA bytea variable-length byte array (null-byte safe)
-"char" char one character
-</PRE>
-
+<CENTER>
+<TABLE BORDER=1>
+<TR><TH>Type</TH><TH>Internal Name</TH><TH>Notes</TH></TR>
+<TR><TD>VARCHAR(n)</TD><TD>varchar</TD><TD>size specifies maximum
+length, no padding</TD></TR>
+<TR><TD>CHAR(n)</TD><TD>bpchar</TD><TD>blank padded to the specified
+fixed length</TD></TR>
+<TR><TD>TEXT</TD><TD>text</TD><TD>no specific upper limit on
+length</TD></TR>
+<TR><TD>BYTEA</TD><TD>bytea</TD><TD>variable-length byte array
+(null-byte safe)</TD></TR>
+<TR><TD>"char"</TD><TD>char</TD><TD>one character</TD></TR>
+</TABLE>
+</CENTER>
<P>You will see the internal name when examining system catalogs
and in some error messages.</P>
@@ -884,10 +892,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
</PRE>
See the <I>create_sequence</I> manual page for more information
- about sequences. You can also use each row's <I>OID</I> field as a
- unique value. However, if you need to dump and reload the database,
- you need to use <I>pg_dump</I>'s <I>-o</I> option or <SMALL>COPY
- WITH OIDS</SMALL> option to preserve the <SMALL>OID</SMALL>s.
+ about sequences.
<H4><A name="4.11.2">4.11.2</A>) How do I get the value of a
<SMALL>SERIAL</SMALL> insert?</H4>
@@ -918,19 +923,11 @@ BYTEA bytea variable-length byte array (null-byte safe)
new_id = execute("SELECT currval('person_id_seq')");
</PRE>
- <P>Finally, you could use the <A href="#4.12"><SMALL>OID</SMALL></A>
- returned from the <SMALL>INSERT</SMALL> statement to look up the
- default value, though this is probably the least portable approach,
- and the oid value will wrap around when it reaches 4 billion.
- In Perl, using DBI with the DBD::Pg module, the oid value is made
- available via <I>$sth->{pg_oid_status}</I> after
- <I>$sth->execute()</I>.</P>
-
<H4><A name="4.11.3">4.11.3</A>) Doesn't <I>currval()</I>
lead to a race condition with other users?</H4>
<P>No. <I>currval()</I> returns the current value assigned by your
- backend, not by all users.</P>
+ session, not by all sessions.</P>
<H4><A name="4.11.4">4.11.4</A>) Why aren't my sequence numbers
reused on transaction abort? Why are there gaps in the numbering of
@@ -964,36 +961,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
are modified or reloaded. They are used by index entries to point
to physical rows.</P>
- <H4><A name="4.13">4.13</A>) What is the meaning of some of the
- terms used in PostgreSQL?</H4>
-
- <P>Some of the source code and older documentation use terms that
- have more common usage. Here are some:</P>
-
- <UL>
- <LI>table, relation, class</LI>
-
- <LI>row, record, tuple</LI>
-
- <LI>column, field, attribute</LI>
-
- <LI>retrieve, select</LI>
-
- <LI>replace, update</LI>
-
- <LI>append, insert</LI>
-
- <LI><SMALL>OID</SMALL>, serial value</LI>
-
- <LI>portal, cursor</LI>
-
- <LI>range variable, table name, table alias</LI>
- </UL>
-
- <P>A list of general database terms can be found at: <A href=
- "http://hea-www.harvard.edu/MST/simul/software/docs/pkgs/pgsql/glossary/glossary.html">http://hea-www.harvard.edu/MST/simul/software/docs/pkgs/pgsql/glossary/glossary.html</A></P>
-
- <H4><A name="4.14">4.14</A>) Why do I get the error <I>"ERROR:
+ <H4><A name="4.13">4.13</A>) Why do I get the error <I>"ERROR:
Memory exhausted in AllocSetAlloc()"</I>?</H4>
<P>You probably have run out of virtual memory on your system,
@@ -1012,12 +980,12 @@ BYTEA bytea variable-length byte array (null-byte safe)
backend is returning too much data, try it before starting the
client.
- <H4><A name="4.15">4.15</A>) How do I tell what PostgreSQL version
+ <H4><A name="4.14">4.14</A>) How do I tell what PostgreSQL version
I am running?</H4>
<P>From <I>psql</I>, type <CODE>SELECT version();</CODE></P>
- <H4><A name="4.16">4.16</A>) Why does my large-object operations
+ <H4><A name="4.15">4.15</A>) Why does my large-object operations
get <I>"invalid large obj descriptor"</I>?</H4>
<P>You need to put <CODE>BEGIN WORK</CODE> and <CODE>COMMIT</CODE>
@@ -1033,7 +1001,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
<P>If you are using a client interface like <SMALL>ODBC</SMALL> you
may need to set <CODE>auto-commit off.</CODE></P>
- <H4><A name="4.17">4.17</A>) How do I create a column that will
+ <H4><A name="4.16">4.16</A>) How do I create a column that will
default to the current time?</H4>
<P>Use <I>CURRENT_TIMESTAMP</I>:</P>
@@ -1041,7 +1009,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP );
</PRE>
- <H4><A name="4.18">4.18</A>) How do I perform an outer join?</H4>
+ <H4><A name="4.17">4.17</A>) How do I perform an outer join?</H4>
<P>PostgreSQL supports outer joins using the SQL standard syntax.
Here are two examples:</P>
@@ -1081,7 +1049,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
ORDER BY col1
</PRE>
- <H4><A name="4.19">4.19</A>) How do I perform queries using
+ <H4><A name="4.18">4.18</A>) How do I perform queries using
multiple databases?</H4>
<P>There is no way to query a database other than the current one.
@@ -1093,7 +1061,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
connections to different databases and merge the results on the
client side.</P>
- <H4><A name="4.20">4.20</A>) How do I return multiple rows or
+ <H4><A name="4.19">4.19</A>) How do I return multiple rows or
columns from a function?</H4>
<P>In 7.3, you can easily return multiple rows or columns from a
@@ -1101,7 +1069,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
<a href="http://techdocs.postgresql.org/guides/SetReturningFunctions">
http://techdocs.postgresql.org/guides/SetReturningFunctions</a>.
- <H4><A name="4.21">4.21</A>) Why can't I reliably create/drop
+ <H4><A name="4.20">4.20</A>) Why can't I reliably create/drop
temporary tables in PL/PgSQL functions?</H4>
<P>PL/PgSQL caches function contents, and an unfortunate side effect
is that if a PL/PgSQL function accesses a temporary table, and that
@@ -1111,7 +1079,7 @@ BYTEA bytea variable-length byte array (null-byte safe)
<SMALL>EXECUTE</SMALL> for temporary table access in PL/PgSQL. This
will cause the query to be reparsed every time.</P>
- <H4><A name="4.22">4.22</A>) What encryption options are available?
+ <H4><A name="4.21">4.21</A>) What encryption options are available?
</H4>
<UL>
<LI><I>contrib/pgcrypto</I> contains many encryption functions for