diff options
| author | Bruce Momjian <bruce@momjian.us> | 2002-01-04 05:44:45 +0000 | 
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2002-01-04 05:44:45 +0000 | 
| commit | 0b79ed27457bda0f2545257225923488ca72a453 (patch) | |
| tree | 640ba6b9986a254de24df39b4fa23123ef9f9afc /doc/src/FAQ/FAQ.html | |
| parent | b5213b5c3715d96dd8f8fd1d33a8d0d0adf17147 (diff) | |
Update FAQ.
Diffstat (limited to 'doc/src/FAQ/FAQ.html')
| -rw-r--r-- | doc/src/FAQ/FAQ.html | 121 | 
1 files changed, 55 insertions, 66 deletions
| diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html index dd5eb71073a..1133ab77d2f 100644 --- a/doc/src/FAQ/FAQ.html +++ b/doc/src/FAQ/FAQ.html @@ -11,7 +11,7 @@    alink="#0000FF">      <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> -    <P>Last updated: Wed Dec  5 00:41:12 EST 2001</P> +    <P>Last updated: Fri Jan  4 00:44:42 EST 2002</P>      <P>Current maintainer: Bruce Momjian (<A href=      "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR> @@ -89,57 +89,55 @@      <CENTER>        <H2>Operational Questions</H2>      </CENTER> -    <A href="#4.1">4.1</A>) Why is the system confused about commas, -    decimal points, and date formats.<BR> -     <A href="#4.2">4.2</A>) What is the exact difference between +     <A href="#4.1">4.1</A>) What is the difference between      binary cursors and normal cursors?<BR> -     <A href="#4.3">4.3</A>) How do I <SMALL>SELECT</SMALL> only the +     <A href="#4.2">4.2</A>) How do I <SMALL>SELECT</SMALL> only the      first few rows of a query?<BR> -     <A href="#4.4">4.4</A>) How do I get a list of tables or other +     <A href="#4.3">4.3</A>) How do I get a list of tables or other      things I can see in <I>psql?</I><BR> -     <A href="#4.5">4.5</A>) How do you remove a column from a +     <A href="#4.4">4.4</A>) How do you remove a column from a      table?<BR> -     <A href="#4.6">4.6</A>) What is the maximum size for a row, table, +     <A href="#4.5">4.5</A>) What is the maximum size for a row, table,      database?<BR> -     <A href="#4.7">4.7</A>) How much database disk space is required +     <A href="#4.6">4.6</A>) How much database disk space is required      to store data from a typical text file?<BR> -     <A href="#4.8">4.8</A>) How do I find out what tables or indexes +     <A href="#4.7">4.7</A>) How do I find out what tables or indexes      are defined in the database?<BR> -     <A href="#4.9">4.9</A>) My queries are slow or don't make use of +     <A href="#4.8">4.8</A>) My queries are slow or don't make use of      the indexes. Why?<BR> -     <A href="#4.10">4.10</A>) How do I see how the query optimizer is +     <A href="#4.9">4.9</A>) How do I see how the query optimizer is      evaluating my query?<BR> -     <A href="#4.11">4.11</A>) What is an R-tree index?<BR> -     <A href="#4.12">4.12</A>) What is the Genetic Query Optimizer?<BR> -     <A href="#4.13">4.13</A>) How do I perform regular expression +     <A href="#4.10">4.10</A>) What is an R-tree index?<BR> +     <A href="#4.11">4.11</A>) What is the Genetic Query Optimizer?<BR> +     <A href="#4.12">4.12</A>) How do I perform regular expression      searches and case-insensitive regular expression searches? How do I      use an index for case-insensitive searches?<BR> -     <A href="#4.14">4.14</A>) In a query, how do I detect if a field +     <A href="#4.13">4.13</A>) In a query, how do I detect if a field      is <SMALL>NULL</SMALL>?<BR> -     <A href="#4.15">4.15</A>) What is the difference between the +     <A href="#4.14">4.14</A>) What is the difference between the      various character types?<BR> -     <A href="#4.16.1">4.16.1</A>) How do I create a +     <A href="#4.15.1">4.15.1</A>) How do I create a      serial/auto-incrementing field?<BR> -     <A href="#4.16.2">4.16.2</A>) How do I get the value of a +     <A href="#4.15.2">4.15.2</A>) How do I get the value of a      <SMALL>SERIAL</SMALL> insert?<BR> -     <A href="#4.16.3">4.16.3</A>) Don't <I>currval()</I> and +     <A href="#4.15.3">4.15.3</A>) Don't <I>currval()</I> and      <I>nextval()</I> lead to a race condition with other users?<BR> -     <A href="#4.17">4.17</A>) What is an <SMALL>OID</SMALL>? What is a +     <A href="#4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is a      <SMALL>TID</SMALL>?<BR> -     <A href="#4.18">4.18</A>) What is the meaning of some of the terms +     <A href="#4.17">4.17</A>) What is the meaning of some of the terms      used in PostgreSQL?<BR> -     <A href="#4.19">4.19</A>) Why do I get the error <I>"ERROR:  +     <A href="#4.18">4.18</A>) Why do I get the error <I>"ERROR:        Memory exhausted in AllocSetAlloc()?"</I><BR> -     <A href="#4.20">4.20</A>) How do I tell what PostgreSQL version I +     <A href="#4.19">4.19</A>) How do I tell what PostgreSQL version I      am running? <BR> -     <A href="#4.21">4.21</A>) My large-object operations get +     <A href="#4.20">4.20</A>) My large-object operations get      <I>invalid large obj descriptor.</I> Why?<BR> -     <A href="#4.22">4.22</A>) How do I create a column that will +     <A href="#4.21">4.21</A>) How do I create a column that will      default to the current time?<BR> -     <A href="#4.23">4.23</A>) Why are my subqueries using +     <A href="#4.22">4.22</A>) Why are my subqueries using      <CODE><SMALL>IN</SMALL></CODE> so slow?<BR> -     <A href="#4.24">4.24</A>) How do I perform an outer join?<BR> -     <A href="#4.25">4.25</A>) How do I perform queries using multiple databases?<BR> +     <A href="#4.23">4.23</A>) How do I perform an outer join?<BR> +     <A href="#4.24">4.24</A>) How do I perform queries using multiple databases?<BR>      <CENTER> @@ -788,22 +786,13 @@        <H2>Operational Questions</H2>      </CENTER> -    <H4><A name="4.1">4.1</A>) Why is system confused about commas, -    decimal points, and date formats.</H4> - -    <P>Check your locale configuration. PostgreSQL uses the locale -    setting of the user that ran the <I>postmaster</I> process. There -    are postgres and psql <SMALL>SET</SMALL> commands to control the -    date format. Set those accordingly for your operating -    environment.</P> - -    <H4><A name="4.2">4.2</A>) What is the exact difference between +    <H4><A name="4.1">4.1</A>) What is the difference between      binary cursors and normal cursors?</H4>      <P>See the <SMALL>DECLARE</SMALL> manual page for a      description.</P> -    <H4><A name="4.3">4.3</A>) How do I <SMALL>SELECT</SMALL> only the +    <H4><A name="4.2">4.2</A>) How do I <SMALL>SELECT</SMALL> only the      first few rows of a query?</H4>      <P>See the <SMALL>FETCH</SMALL> manual page, or use @@ -816,7 +805,7 @@      records requested, or the entire query may have to be evaluated      until the desired rows have been generated.</P> -    <H4><A name="4.4">4.4</A>) How do I get a list of tables or other +    <H4><A name="4.3">4.3</A>) How do I get a list of tables or other      things I can see in <I>psql?</I><BR>      </H4> @@ -827,7 +816,7 @@      <I>-E</I> option so it will print out the queries it uses to      execute the commands you give.</P> -    <H4><A name="4.5">4.5</A>) How do you remove a column from a +    <H4><A name="4.4">4.4</A>) How do you remove a column from a      table?</H4>      <P>We do not support <SMALL>ALTER TABLE DROP COLUMN,</SMALL> but do @@ -840,7 +829,7 @@      ALTER TABLE new_table RENAME TO old_table;  </PRE> -    <H4><A name="4.6">4.6</A>) What is the maximum size for a row, +    <H4><A name="4.5">4.5</A>) What is the maximum size for a row,      table, database?</H4>      <P>These are the limits:</P> @@ -864,7 +853,7 @@      <P>The maximum table size and maximum number of columns can be      increased if the default block size is increased to 32k.</P> -    <H4><A name="4.7">4.7</A>) How much database disk space is required +    <H4><A name="4.6">4.6</A>) How much database disk space is required      to store data from a typical text file?<BR>      </H4> @@ -897,7 +886,7 @@      <P>Indexes do not require as much overhead, but do contain the data      that is being indexed, so they can be large also.</P> -    <H4><A name="4.8">4.8</A>) How do I find out what tables or indexes +    <H4><A name="4.7">4.7</A>) How do I find out what tables or indexes      are defined in the database?</H4>      <P><I>psql</I> has a variety of backslash commands to show such @@ -907,7 +896,7 @@      illustrates many of the <SMALL>SELECT</SMALL>s needed to get      information from the database system tables.</P> -    <H4><A name="4.9">4.9</A>) My queries are slow or don't make use of +    <H4><A name="4.8">4.8</A>) My queries are slow or don't make use of      the indexes. Why?</H4>      <P>PostgreSQL does not automatically maintain statistics. @@ -937,12 +926,12 @@      <I>~</I>(regular expression searches) should start with      <I>^.</I></P> -    <H4><A name="4.10">4.10</A>) How do I see how the query optimizer +    <H4><A name="4.9">4.9</A>) How do I see how the query optimizer      is evaluating my query?</H4>      <P>See the <SMALL>EXPLAIN</SMALL> manual page.</P> -    <H4><A name="4.11">4.11</A>) What is an R-tree index?</H4> +    <H4><A name="4.10">4.10</A>) What is an R-tree index?</H4>      <P>An R-tree index is used for indexing spatial data. A hash index      can't handle range searches. A B-tree index only handles range @@ -967,7 +956,7 @@      practice, extending R-trees requires a bit of work and we don't      currently have any documentation on how to do it.</P> -    <H4><A name="4.12">4.12</A>) What is the Genetic Query +    <H4><A name="4.11">4.11</A>) What is the Genetic Query      Optimizer?</H4>      <P>The <SMALL>GEQO</SMALL> module speeds query optimization when @@ -975,7 +964,7 @@      the handling of large join queries through nonexhaustive      search.</P> -    <H4><A name="4.13">4.13</A>) How do I perform regular expression +    <H4><A name="4.12">4.12</A>) How do I perform regular expression      searches and case-insensitive regular expression searches?  How do I      use an index for case-insensitive searches?</H4> @@ -999,12 +988,12 @@      CREATE INDEX tabindex on tab (lower(col));      </PRE> -    <H4><A name="4.14">4.14</A>) In a query, how do I detect if a field +    <H4><A name="4.13">4.13</A>) In a query, how do I detect if a field      is <SMALL>NULL</SMALL>?</H4>      <P>You test the column with <SMALL>IS NULL</SMALL>IS NOT NULL.</P> -    <H4><A name="4.15">4.15</A>) What is the difference between the +    <H4><A name="4.14">4.14</A>) What is the difference between the      various character types?</H4>  <PRE>  Type            Internal Name   Notes @@ -1034,7 +1023,7 @@ BYTEA           bytea           variable-length byte array (null-safe)      binary data, particularly values that include <SMALL>NULL</SMALL>      bytes.</P> -    <H4><A name="4.16.1">4.16.1</A>) How do I create a +    <H4><A name="4.15.1">4.15.1</A>) How do I create a      serial/auto-incrementing field?</H4>      <P>PostgreSQL supports a <SMALL>SERIAL</SMALL> data type. It @@ -1064,13 +1053,13 @@ BYTEA           bytea           variable-length byte array (null-safe)      <P><A href="http://www.PostgreSQL.org/docs/aw_pgsql_book">Numbering      Rows.</A></P> -    <H4><A name="4.16.2">4.16.2</A>) How do I get the value of a +    <H4><A name="4.15.2">4.15.2</A>) How do I get the value of a      <SMALL>SERIAL</SMALL> insert?</H4>      <P>One approach is to to retrieve the next <SMALL>SERIAL</SMALL>      value from the sequence object with the <I>nextval()</I> function      <I>before</I> inserting and then insert it explicitly. Using the -    example table in <A href="#4.16.1">4.16.1</A>, that might look like +    example table in <A href="#4.15.1">4.15.1</A>, that might look like      this in Perl:</P>  <PRE>      new_id = output of "SELECT nextval('person_id_seq')" @@ -1091,20 +1080,20 @@ BYTEA           bytea           variable-length byte array (null-safe)      INSERT INTO person (name) VALUES ('Blaise Pascal');      new_id = output of "SELECT currval('person_id_seq')";  </PRE> -    Finally, you could use the <A href="#4.17"><SMALL>OID</SMALL></A> +    Finally, you could use the <A href="#4.16"><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.      In Perl, using DBI with Edmund Mergl's DBD::Pg module, the oid      value is made available via <I>$sth->{pg_oid_status} after      $sth->execute().</I>  -    <H4><A name="4.16.3">4.16.3</A>) Don't <I>currval()</I> and +    <H4><A name="4.15.3">4.15.3</A>) Don't <I>currval()</I> and      <I>nextval()</I> lead to a race condition with other users?</H4>      <P>No. Currval() returns the current value assigned by your      backend, not by all users.</P> -    <H4><A name="4.17">4.17</A>) What is an <SMALL>OID</SMALL>? What is +    <H4><A name="4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is      a <SMALL>TID</SMALL>?</H4>      <P><SMALL>OID</SMALL>s are PostgreSQL's answer to unique row ids. @@ -1149,7 +1138,7 @@ BYTEA           bytea           variable-length byte array (null-safe)      or reloaded. They are used by index entries to point to physical      rows.</P> -    <H4><A name="4.18">4.18</A>) What is the meaning of some of the +    <H4><A name="4.17">4.17</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 @@ -1178,7 +1167,7 @@ BYTEA           bytea           variable-length byte array (null-safe)      <P>A list of general database terms can be found at: <A href=      "http://www.comptechnews.com/~reaster/dbdesign.html">http://www.comptechnews.com/~reaster/dbdesign.html</A></P> -    <H4><A name="4.19">4.19</A>) Why do I get the error <I>"ERROR:  +    <H4><A name="4.18">4.18</A>) Why do I get the error <I>"ERROR:        Memory exhausted in AllocSetAlloc()?"</I><BR>      </H4> @@ -1198,13 +1187,13 @@ BYTEA           bytea           variable-length byte array (null-safe)      backend is returning too much data, try it before starting the      client.  -    <H4><A name="4.20">4.20</A>) How do I tell what PostgreSQL version +    <H4><A name="4.19">4.19</A>) How do I tell what PostgreSQL version      I am running?<BR>      </H4>      <P>From <I>psql,</I> type <CODE>select version();</CODE></P> -    <H4><A name="4.21">4.21</A>) My large-object operations get +    <H4><A name="4.20">4.20</A>) My large-object operations get      <I>invalid large obj descriptor.</I> Why?<BR>      </H4> @@ -1221,7 +1210,7 @@ BYTEA           bytea           variable-length byte array (null-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="4.22">4.22</A>) How do I create a column that will +    <H4><A name="4.21">4.21</A>) How do I create a column that will      default to the current time?<BR>      </H4> @@ -1231,7 +1220,7 @@ BYTEA           bytea           variable-length byte array (null-safe)  </CODE>  </PRE> -    <H4><A name="4.23">4.23</A>) Why are my subqueries using +    <H4><A name="4.22">4.22</A>) Why are my subqueries using      <CODE><SMALL>IN</SMALL></CODE> so slow?<BR>      </H4> @@ -1254,7 +1243,7 @@ BYTEA           bytea           variable-length byte array (null-safe)  </PRE>      We hope to fix this limitation in a future release.  -    <H4><A name="4.24">4.24</A>) How do I perform an outer join?<BR> +    <H4><A name="4.23">4.23</A>) How do I perform an outer join?<BR>      </H4>      <P>PostgreSQL 7.1 and later supports outer joins using the SQL @@ -1295,7 +1284,7 @@ BYTEA           bytea           variable-length byte array (null-safe)      ORDER BY col1  </PRE> -    <H4><A href="#4.25">4.25</A>) How do I perform queries +    <H4><A href="#4.24">4.24</A>) How do I perform queries      using multiple databases?</H4>      <P>There is no way to query any database except the current one. | 
