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postgresql8.3-docs-8.3.6-2mdv2008.1.x86_64.rpm

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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="FUNCTIONS-INFO"
>9.22. System Information Functions</A
></H1
><P
>   <A
HREF="functions-info.html#FUNCTIONS-INFO-SESSION-TABLE"
>Table 9-44</A
> shows several
   functions that extract session and system information.
  </P
><P
>   In addition to the functions listed in this section, there are a number of
   functions related to the statistics system that also provide system
   information. See <A
HREF="monitoring-stats.html#MONITORING-STATS-VIEWS"
>Section 26.2.2</A
> for more
   information.
  </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-INFO-SESSION-TABLE"
></A
><P
><B
>Table 9-44. Session Information Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>current_database</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>name of current database</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>current_schema</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>name of current schema</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>current_schemas</CODE
>(<TT
CLASS="TYPE"
>boolean</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>name[]</TT
></TD
><TD
>names of schemas in search path optionally including implicit schemas</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>current_user</CODE
></TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>user name of current execution context</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>inet_client_addr</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>inet</TT
></TD
><TD
>address of the remote connection</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>inet_client_port</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>port of the remote connection</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>inet_server_addr</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>inet</TT
></TD
><TD
>address of the local connection</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>inet_server_port</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>int</TT
></TD
><TD
>port of the local connection</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_my_temp_schema</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
>OID of session's temporary schema, or 0 if none</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_is_other_temp_schema</CODE
>(<TT
CLASS="TYPE"
>oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is schema another session's temporary schema?</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_postmaster_start_time</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>timestamp with time zone</TT
></TD
><TD
>server start time</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>session_user</CODE
></TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>session user name</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>user</CODE
></TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>equivalent to <CODE
CLASS="FUNCTION"
>current_user</CODE
></TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>version</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
><SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> version information</TD
></TR
></TBODY
></TABLE
></DIV
><A
NAME="AEN15752"
></A
><A
NAME="AEN15755"
></A
><A
NAME="AEN15758"
></A
><A
NAME="AEN15761"
></A
><A
NAME="AEN15763"
></A
><A
NAME="AEN15765"
></A
><P
>    The <CODE
CLASS="FUNCTION"
>session_user</CODE
> is normally the user who initiated
    the current database connection; but superusers can change this setting
    with <A
HREF="sql-set-session-authorization.html"
><I
>SET SESSION AUTHORIZATION</I
></A
>.
    The <CODE
CLASS="FUNCTION"
>current_user</CODE
> is the user identifier
    that is applicable for permission checking. Normally, it is equal
    to the session user, but it can be changed with
    <A
HREF="sql-set-role.html"
><I
>SET ROLE</I
></A
>.
    It also changes during the execution of
    functions with the attribute <TT
CLASS="LITERAL"
>SECURITY DEFINER</TT
>.
    In Unix parlance, the session user is the <SPAN
CLASS="QUOTE"
>"real user"</SPAN
> and
    the current user is the <SPAN
CLASS="QUOTE"
>"effective user"</SPAN
>.
   </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>     <CODE
CLASS="FUNCTION"
>current_user</CODE
>, <CODE
CLASS="FUNCTION"
>session_user</CODE
>, and
     <CODE
CLASS="FUNCTION"
>user</CODE
> have special syntactic status in <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
>:
     they must be called without trailing parentheses.
    </P
></BLOCKQUOTE
></DIV
><P
>    <CODE
CLASS="FUNCTION"
>current_schema</CODE
> returns the name of the schema that is
    at the front of the search path (or a null value if the search path is
    empty).  This is the schema that will be used for any tables or
    other named objects that are created without specifying a target schema.
    <CODE
CLASS="FUNCTION"
>current_schemas(boolean)</CODE
> returns an array of the names of all
    schemas presently in the search path.  The Boolean option determines whether or not
    implicitly included system schemas such as <TT
CLASS="LITERAL"
>pg_catalog</TT
> are included in the search 
    path returned.
   </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>     The search path can be altered at run time.  The command is:
</P><PRE
CLASS="PROGRAMLISTING"
>SET search_path TO <TT
CLASS="REPLACEABLE"
><I
>schema</I
></TT
> [<SPAN
CLASS="OPTIONAL"
>, <TT
CLASS="REPLACEABLE"
><I
>schema</I
></TT
>, ...</SPAN
>]</PRE
><P>
    </P
></BLOCKQUOTE
></DIV
><A
NAME="AEN15791"
></A
><A
NAME="AEN15793"
></A
><A
NAME="AEN15795"
></A
><A
NAME="AEN15797"
></A
><P
>     <CODE
CLASS="FUNCTION"
>inet_client_addr</CODE
> returns the IP address of the
     current client, and <CODE
CLASS="FUNCTION"
>inet_client_port</CODE
> returns the
     port number.
     <CODE
CLASS="FUNCTION"
>inet_server_addr</CODE
> returns the IP address on which
     the server accepted the current connection, and
     <CODE
CLASS="FUNCTION"
>inet_server_port</CODE
> returns the port number.
     All these functions return NULL if the current connection is via a
     Unix-domain socket.
   </P
><A
NAME="AEN15804"
></A
><A
NAME="AEN15806"
></A
><P
>    <CODE
CLASS="FUNCTION"
>pg_my_temp_schema</CODE
> returns the OID of the current
    session's temporary schema, or 0 if it has none (because it has not
    created any temporary tables).
    <CODE
CLASS="FUNCTION"
>pg_is_other_temp_schema</CODE
> returns true if the
    given OID is the OID of any other session's temporary schema.
    (This can be useful, for example, to exclude other sessions' temporary
    tables from a catalog display.)
   </P
><A
NAME="AEN15811"
></A
><P
>     <CODE
CLASS="FUNCTION"
>pg_postmaster_start_time</CODE
> returns the
     <TT
CLASS="TYPE"
>timestamp with time zone</TT
> when the
     server started.
   </P
><A
NAME="AEN15816"
></A
><P
>    <CODE
CLASS="FUNCTION"
>version</CODE
> returns a string describing the
    <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server's version.
   </P
><A
NAME="AEN15821"
></A
><P
>   <A
HREF="functions-info.html#FUNCTIONS-INFO-ACCESS-TABLE"
>Table 9-45</A
> lists functions that
   allow the user to query object access privileges programmatically.
   See <A
HREF="ddl-priv.html"
>Section 5.6</A
> for more information about
   privileges.
  </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-INFO-ACCESS-TABLE"
></A
><P
><B
>Table 9-45. Access Privilege Inquiry Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_database_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>database</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for database</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_database_privilege</CODE
>(<TT
CLASS="PARAMETER"
>database</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for database</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_function_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>function</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for function</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_function_privilege</CODE
>(<TT
CLASS="PARAMETER"
>function</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for function</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_language_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>language</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for language</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_language_privilege</CODE
>(<TT
CLASS="PARAMETER"
>language</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for language</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_schema_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>schema</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for schema</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_schema_privilege</CODE
>(<TT
CLASS="PARAMETER"
>schema</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for schema</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>table</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for table</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>(<TT
CLASS="PARAMETER"
>table</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for table</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_tablespace_privilege</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>tablespace</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for tablespace</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>has_tablespace_privilege</CODE
>(<TT
CLASS="PARAMETER"
>tablespace</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for tablespace</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_has_role</CODE
>(<TT
CLASS="PARAMETER"
>user</TT
>,
                                  <TT
CLASS="PARAMETER"
>role</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does user have privilege for role</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_has_role</CODE
>(<TT
CLASS="PARAMETER"
>role</TT
>,
                                  <TT
CLASS="PARAMETER"
>privilege</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does current user have privilege for role</TD
></TR
></TBODY
></TABLE
></DIV
><A
NAME="AEN15969"
></A
><A
NAME="AEN15971"
></A
><A
NAME="AEN15973"
></A
><A
NAME="AEN15975"
></A
><A
NAME="AEN15977"
></A
><A
NAME="AEN15979"
></A
><A
NAME="AEN15981"
></A
><P
>    <CODE
CLASS="FUNCTION"
>has_database_privilege</CODE
> checks whether a user
    can access a database in a particular way.  The possibilities for its
    arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>CREATE</TT
>,
    <TT
CLASS="LITERAL"
>CONNECT</TT
>,
    <TT
CLASS="LITERAL"
>TEMPORARY</TT
>, or
    <TT
CLASS="LITERAL"
>TEMP</TT
> (which is equivalent to
    <TT
CLASS="LITERAL"
>TEMPORARY</TT
>).
   </P
><P
>    <CODE
CLASS="FUNCTION"
>has_function_privilege</CODE
> checks whether a user
    can access a function in a particular way.  The possibilities for its
    arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    When specifying a function by a text string rather than by OID,
    the allowed input is the same as for the <TT
CLASS="TYPE"
>regprocedure</TT
> data type
    (see <A
HREF="datatype-oid.html"
>Section 8.16</A
>).
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>EXECUTE</TT
>.
    An example is:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute');</PRE
><P>
   </P
><P
>    <CODE
CLASS="FUNCTION"
>has_language_privilege</CODE
> checks whether a user
    can access a procedural language in a particular way.  The possibilities
    for its arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>USAGE</TT
>.
   </P
><P
>    <CODE
CLASS="FUNCTION"
>has_schema_privilege</CODE
> checks whether a user
    can access a schema in a particular way.  The possibilities for its
    arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>CREATE</TT
> or
    <TT
CLASS="LITERAL"
>USAGE</TT
>.
   </P
><P
>    <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
> checks whether a user
    can access a table in a particular way.  The user can be
    specified by name or by OID
    (<TT
CLASS="LITERAL"
>pg_authid.oid</TT
>), or if the argument is
    omitted
    <CODE
CLASS="FUNCTION"
>current_user</CODE
> is assumed.  The table can be specified
    by name or by OID.  (Thus, there are actually six variants of
    <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>, which can be distinguished by
    the number and types of their arguments.)  When specifying by name,
    the name can be schema-qualified if necessary.
    The desired access privilege type
    is specified by a text string, which must evaluate to one of the
    values <TT
CLASS="LITERAL"
>SELECT</TT
>, <TT
CLASS="LITERAL"
>INSERT</TT
>,
    <TT
CLASS="LITERAL"
>UPDATE</TT
>, <TT
CLASS="LITERAL"
>DELETE</TT
>,
    <TT
CLASS="LITERAL"
>REFERENCES</TT
>, or <TT
CLASS="LITERAL"
>TRIGGER</TT
>.
    (Case of the string is not significant, however.)
    An example is:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT has_table_privilege('myschema.mytable', 'select');</PRE
><P>
   </P
><P
>    <CODE
CLASS="FUNCTION"
>has_tablespace_privilege</CODE
> checks whether a user
    can access a tablespace in a particular way.  The possibilities for its
    arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>CREATE</TT
>.
   </P
><P
>    <CODE
CLASS="FUNCTION"
>pg_has_role</CODE
> checks whether a user
    can access a role in a particular way.  The possibilities for its
    arguments are analogous to <CODE
CLASS="FUNCTION"
>has_table_privilege</CODE
>.
    The desired access privilege type must evaluate to
    <TT
CLASS="LITERAL"
>MEMBER</TT
> or
    <TT
CLASS="LITERAL"
>USAGE</TT
>.
    <TT
CLASS="LITERAL"
>MEMBER</TT
> denotes direct or indirect membership in
    the role (that is, the right to do <TT
CLASS="COMMAND"
>SET ROLE</TT
>), while
    <TT
CLASS="LITERAL"
>USAGE</TT
> denotes whether the privileges of the role
    are immediately available without doing <TT
CLASS="COMMAND"
>SET ROLE</TT
>.
   </P
><P
>   To test whether a user holds a grant option on the privilege,
   append <TT
CLASS="LITERAL"
>WITH GRANT OPTION</TT
> to the privilege key
   word; for example <TT
CLASS="LITERAL"
>'UPDATE WITH GRANT OPTION'</TT
>.
  </P
><P
>   <A
HREF="functions-info.html#FUNCTIONS-INFO-SCHEMA-TABLE"
>Table 9-46</A
> shows functions that
   determine whether a certain object is <I
CLASS="FIRSTTERM"
>visible</I
> in the
   current schema search path.
   For example, a table is said to be visible if its
   containing schema is in the search path and no table of the same
   name appears earlier in the search path.  This is equivalent to the
   statement that the table can be referenced by name without explicit
   schema qualification.  To list the names of all visible tables:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);</PRE
><P>
  </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-INFO-SCHEMA-TABLE"
></A
><P
><B
>Table 9-46. Schema Visibility Inquiry Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_conversion_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>conversion_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is conversion visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_function_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>function_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is function visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_operator_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>operator_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is operator visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_opclass_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>opclass_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is operator class visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_table_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>table_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is table visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_ts_config_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>config_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is text search configuration visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_ts_dict_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>dict_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is text search dictionary visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_ts_parser_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>parser_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is text search parser visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_ts_template_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>template_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is text search template visible in search path</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_type_is_visible</CODE
>(<TT
CLASS="PARAMETER"
>type_oid</TT
>)</TT
>
       </TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is type (or domain) visible in search path</TD
></TR
></TBODY
></TABLE
></DIV
><A
NAME="AEN16128"
></A
><A
NAME="AEN16130"
></A
><A
NAME="AEN16132"
></A
><A
NAME="AEN16134"
></A
><A
NAME="AEN16136"
></A
><A
NAME="AEN16138"
></A
><A
NAME="AEN16140"
></A
><A
NAME="AEN16142"
></A
><A
NAME="AEN16144"
></A
><A
NAME="AEN16146"
></A
><P
>    Each function performs the visibility check for one type of database
    object.  Note that <CODE
CLASS="FUNCTION"
>pg_table_is_visible</CODE
> can also be used
    with views, indexes and sequences; <CODE
CLASS="FUNCTION"
>pg_type_is_visible</CODE
>
    can also be used with domains. For functions and operators, an object in
    the search path is visible if there is no object of the same name
    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>and argument data type(s)</I
></SPAN
> earlier in the path.  For operator
    classes, both name and associated index access method are considered.
   </P
><P
>    All these functions require object OIDs to identify the object to be
    checked.  If you want to test an object by name, it is convenient to use
    the OID alias types (<TT
CLASS="TYPE"
>regclass</TT
>, <TT
CLASS="TYPE"
>regtype</TT
>,
    <TT
CLASS="TYPE"
>regprocedure</TT
>, <TT
CLASS="TYPE"
>regoperator</TT
>, <TT
CLASS="TYPE"
>regconfig</TT
>,
    or <TT
CLASS="TYPE"
>regdictionary</TT
>),
    for example:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT pg_type_is_visible('myschema.widget'::regtype);</PRE
><P>
    Note that it would not make much sense to test an unqualified name in
    this way &mdash; if the name can be recognized at all, it must be visible.
   </P
><A
NAME="AEN16160"
></A
><A
NAME="AEN16162"
></A
><A
NAME="AEN16164"
></A
><A
NAME="AEN16166"
></A
><A
NAME="AEN16168"
></A
><A
NAME="AEN16170"
></A
><A
NAME="AEN16172"
></A
><A
NAME="AEN16174"
></A
><A
NAME="AEN16176"
></A
><A
NAME="AEN16178"
></A
><P
>   <A
HREF="functions-info.html#FUNCTIONS-INFO-CATALOG-TABLE"
>Table 9-47</A
> lists functions that
   extract information from the system catalogs.
  </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-INFO-CATALOG-TABLE"
></A
><P
><B
>Table 9-47. System Catalog Information Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>format_type</CODE
>(<TT
CLASS="PARAMETER"
>type_oid</TT
>, <TT
CLASS="PARAMETER"
>typemod</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get SQL name of a data type</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_constraintdef</CODE
>(<TT
CLASS="PARAMETER"
>constraint_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get definition of a constraint</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_constraintdef</CODE
>(<TT
CLASS="PARAMETER"
>constraint_oid</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get definition of a constraint</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_expr</CODE
>(<TT
CLASS="PARAMETER"
>expr_text</TT
>, <TT
CLASS="PARAMETER"
>relation_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>decompile internal form of an expression, assuming that any Vars
       in it refer to the relation indicated by the second parameter</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_expr</CODE
>(<TT
CLASS="PARAMETER"
>expr_text</TT
>, <TT
CLASS="PARAMETER"
>relation_oid</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>decompile internal form of an expression, assuming that any Vars
       in it refer to the relation indicated by the second parameter</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_indexdef</CODE
>(<TT
CLASS="PARAMETER"
>index_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get <TT
CLASS="COMMAND"
>CREATE INDEX</TT
> command for index</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_indexdef</CODE
>(<TT
CLASS="PARAMETER"
>index_oid</TT
>, <TT
CLASS="PARAMETER"
>column_no</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get <TT
CLASS="COMMAND"
>CREATE INDEX</TT
> command for index,
       or definition of just one index column when
       <TT
CLASS="PARAMETER"
>column_no</TT
> is not zero</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_ruledef</CODE
>(<TT
CLASS="PARAMETER"
>rule_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get <TT
CLASS="COMMAND"
>CREATE RULE</TT
> command for rule</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_ruledef</CODE
>(<TT
CLASS="PARAMETER"
>rule_oid</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get <TT
CLASS="COMMAND"
>CREATE RULE</TT
> command for rule</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_serial_sequence</CODE
>(<TT
CLASS="PARAMETER"
>table_name</TT
>, <TT
CLASS="PARAMETER"
>column_name</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get name of the sequence that a <TT
CLASS="TYPE"
>serial</TT
> or <TT
CLASS="TYPE"
>bigserial</TT
> column
       uses</TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>pg_get_triggerdef</CODE
>(<TT
CLASS="PARAMETER"
>trigger_oid</TT
>)</TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get <TT
CLASS="COMMAND"
>CREATE [ CONSTRAINT ] TRIGGER</TT
> command for trigger</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_userbyid</CODE
>(<TT
CLASS="PARAMETER"
>roleid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>get role name with given ID</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_viewdef</CODE
>(<TT
CLASS="PARAMETER"
>view_name</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get underlying <TT
CLASS="COMMAND"
>SELECT</TT
> command for view (<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>deprecated</I
></SPAN
>)</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_viewdef</CODE
>(<TT
CLASS="PARAMETER"
>view_name</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get underlying <TT
CLASS="COMMAND"
>SELECT</TT
> command for view (<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>deprecated</I
></SPAN
>)</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_viewdef</CODE
>(<TT
CLASS="PARAMETER"
>view_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get underlying <TT
CLASS="COMMAND"
>SELECT</TT
> command for view</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_get_viewdef</CODE
>(<TT
CLASS="PARAMETER"
>view_oid</TT
>, <TT
CLASS="PARAMETER"
>pretty_bool</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get underlying <TT
CLASS="COMMAND"
>SELECT</TT
> command for view</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>pg_tablespace_databases</CODE
>(<TT
CLASS="PARAMETER"
>tablespace_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>setof oid</TT
></TD
><TD
>get the set of database OIDs that have objects in the tablespace</TD
></TR
></TBODY
></TABLE
></DIV
><P
>   <CODE
CLASS="FUNCTION"
>format_type</CODE
> returns the SQL name of a data type that
   is identified by its type OID and possibly a type modifier.  Pass NULL
   for the type modifier if no specific modifier is known.
  </P
><P
>   <CODE
CLASS="FUNCTION"
>pg_get_constraintdef</CODE
>,
   <CODE
CLASS="FUNCTION"
>pg_get_indexdef</CODE
>, <CODE
CLASS="FUNCTION"
>pg_get_ruledef</CODE
>,
   and <CODE
CLASS="FUNCTION"
>pg_get_triggerdef</CODE
>, respectively reconstruct the
   creating command for a constraint, index, rule, or trigger. (Note that this
   is a decompiled reconstruction, not the original text of the command.)
   <CODE
CLASS="FUNCTION"
>pg_get_expr</CODE
> decompiles the internal form of an
   individual expression, such as the default value for a column.  It can be
   useful when examining the contents of system catalogs.
   <CODE
CLASS="FUNCTION"
>pg_get_viewdef</CODE
> reconstructs the <TT
CLASS="COMMAND"
>SELECT</TT
>
   query that defines a view. Most of these functions come in two variants,
   one of which can optionally <SPAN
CLASS="QUOTE"
>"pretty-print"</SPAN
> the result.  The
   pretty-printed format is more readable, but the default format is more
   likely to be interpreted the same way by future versions of
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>; avoid using pretty-printed output for dump
   purposes.  Passing <TT
CLASS="LITERAL"
>false</TT
> for the pretty-print parameter yields
   the same result as the variant that does not have the parameter at all.
  </P
><P
>   <CODE
CLASS="FUNCTION"
>pg_get_serial_sequence</CODE
> returns the name of the
   sequence associated with a column, or NULL if no sequence is associated
   with the column.  The first input parameter is a table name with
   optional schema, and the second parameter is a column name.  Because
   the first parameter is potentially a schema and table, it is not treated
   as a double-quoted identifier, meaning it is lowercased by default,
   while the second parameter, being just a column name, is treated as
   double-quoted and has its case preserved.  The function returns a value
   suitably formatted for passing to the sequence functions (see <A
HREF="functions-sequence.html"
>Section 9.15</A
>).  This association can be modified or
   removed with <TT
CLASS="COMMAND"
>ALTER SEQUENCE OWNED BY</TT
>.  (The function
   probably should have been called
   <CODE
CLASS="FUNCTION"
>pg_get_owned_sequence</CODE
>; its name reflects the fact
   that it's typically used with <TT
CLASS="TYPE"
>serial</TT
> or <TT
CLASS="TYPE"
>bigserial</TT
>
   columns.)
  </P
><P
>   <CODE
CLASS="FUNCTION"
>pg_get_userbyid</CODE
> extracts a role's name given
   its OID.
  </P
><P
>   <CODE
CLASS="FUNCTION"
>pg_tablespace_databases</CODE
> allows a tablespace to be
   examined. It returns the set of OIDs of databases that have objects stored
   in the tablespace. If this function returns any rows, the tablespace is not
   empty and cannot be dropped. To display the specific objects populating the
   tablespace, you will need to connect to the databases identified by
   <CODE
CLASS="FUNCTION"
>pg_tablespace_databases</CODE
> and query their
   <TT
CLASS="STRUCTNAME"
>pg_class</TT
> catalogs.
  </P
><A
NAME="AEN16377"
></A
><A
NAME="AEN16379"
></A
><A
NAME="AEN16381"
></A
><A
NAME="AEN16383"
></A
><P
>    The functions shown in <A
HREF="functions-info.html#FUNCTIONS-INFO-COMMENT-TABLE"
>Table 9-48</A
>
    extract comments previously stored with the <A
HREF="sql-comment.html"
><I
>COMMENT</I
></A
> command.  A null value is returned if no
    comment could be found matching the specified parameters.
   </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-INFO-COMMENT-TABLE"
></A
><P
><B
>Table 9-48. Comment Information Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>col_description</CODE
>(<TT
CLASS="PARAMETER"
>table_oid</TT
>, <TT
CLASS="PARAMETER"
>column_number</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get comment for a table column</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>obj_description</CODE
>(<TT
CLASS="PARAMETER"
>object_oid</TT
>, <TT
CLASS="PARAMETER"
>catalog_name</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get comment for a database object</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>obj_description</CODE
>(<TT
CLASS="PARAMETER"
>object_oid</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get comment for a database object (<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>deprecated</I
></SPAN
>)</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>shobj_description</CODE
>(<TT
CLASS="PARAMETER"
>object_oid</TT
>, <TT
CLASS="PARAMETER"
>catalog_name</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>get comment for a shared database object</TD
></TR
></TBODY
></TABLE
></DIV
><P
>    <CODE
CLASS="FUNCTION"
>col_description</CODE
> returns the comment for a table column,
    which is specified by the OID of its table and its column number.
    <CODE
CLASS="FUNCTION"
>obj_description</CODE
> cannot be used for table columns since
    columns do not have OIDs of their own.
   </P
><P
>    The two-parameter form of <CODE
CLASS="FUNCTION"
>obj_description</CODE
> returns the
    comment for a database object specified by its OID and the name of the
    containing system catalog.  For example,
    <TT
CLASS="LITERAL"
>obj_description(123456,'pg_class')</TT
>
    would retrieve the comment for a table with OID 123456.
    The one-parameter form of <CODE
CLASS="FUNCTION"
>obj_description</CODE
> requires only
    the object OID.  It is now deprecated since there is no guarantee that
    OIDs are unique across different system catalogs; therefore, the wrong
    comment could be returned.
   </P
><P
>    <CODE
CLASS="FUNCTION"
>shobj_description</CODE
> is used just like
    <CODE
CLASS="FUNCTION"
>obj_description</CODE
> only that it is used for retrieving
    comments on shared objects.  Some system catalogs are global to all
    databases within each cluster and their descriptions are stored globally
    as well.
   </P
><A
NAME="AEN16444"
></A
><A
NAME="AEN16446"
></A
><A
NAME="AEN16448"
></A
><A
NAME="AEN16450"
></A
><A
NAME="AEN16452"
></A
><A
NAME="AEN16454"
></A
><P
>    The functions shown in <A
HREF="functions-info.html#FUNCTIONS-TXID-SNAPSHOT"
>Table 9-49</A
>
    export server internal transaction information to user level.  The main
    use of these functions is to determine which transactions were committed
    between two snapshots.
   </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-TXID-SNAPSHOT"
></A
><P
><B
>Table 9-49. Transaction IDs and snapshots</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Return Type</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_current</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>get current transaction ID</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_current_snapshot</CODE
>()</TT
></TD
><TD
><TT
CLASS="TYPE"
>txid_snapshot</TT
></TD
><TD
>get current snapshot</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_snapshot_xmin</CODE
>(<TT
CLASS="PARAMETER"
>txid_snapshot</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>get xmin of snapshot</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_snapshot_xmax</CODE
>(<TT
CLASS="PARAMETER"
>txid_snapshot</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>bigint</TT
></TD
><TD
>get xmax of snapshot</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_snapshot_xip</CODE
>(<TT
CLASS="PARAMETER"
>txid_snapshot</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>setof bigint</TT
></TD
><TD
>get in-progress transaction IDs in snapshot</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
><CODE
CLASS="FUNCTION"
>txid_visible_in_snapshot</CODE
>(<TT
CLASS="PARAMETER"
>bigint</TT
>, <TT
CLASS="PARAMETER"
>txid_snapshot</TT
>)</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is transaction ID visible in snapshot?</TD
></TR
></TBODY
></TABLE
></DIV
><P
>    The internal transaction ID type (<TT
CLASS="TYPE"
>xid</TT
>) is 32 bits wide and so
    it wraps around every 4 billion transactions.  However, these functions
    export a 64-bit format that is extended with an <SPAN
CLASS="QUOTE"
>"epoch"</SPAN
> counter
    so that it will not wrap around for the life of an installation.
    The data type used by these functions, <TT
CLASS="TYPE"
>txid_snapshot</TT
>,
    stores information about transaction ID
    visibility at a particular moment in time.  Its components are
    described in <A
HREF="functions-info.html#FUNCTIONS-TXID-SNAPSHOT-PARTS"
>Table 9-50</A
>.
   </P
><DIV
CLASS="TABLE"
><A
NAME="FUNCTIONS-TXID-SNAPSHOT-PARTS"
></A
><P
><B
>Table 9-50. Snapshot components</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="TYPE"
>xmin</TT
></TD
><TD
>         Earliest transaction ID (txid) that is still active.  All earlier
         transactions will either be committed and visible, or rolled
         back and dead.
       </TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>xmax</TT
></TD
><TD
>        First as-yet-unassigned txid.  All txids later than this one are
        not yet started as of the time of the snapshot, and thus invisible.
       </TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>xip_list</TT
></TD
><TD
>        Active txids at the time of the snapshot.  All of them are between
        <TT
CLASS="LITERAL"
>xmin</TT
> and <TT
CLASS="LITERAL"
>xmax</TT
>.  A txid that is
        <TT
CLASS="LITERAL"
>xmin &lt;= txid &lt; xmax</TT
> and not in this list was
        already completed at the time of the snapshot, and thus either visible
        or dead according to its commit status.
       </TD
></TR
></TBODY
></TABLE
></DIV
><P
>    <TT
CLASS="TYPE"
>txid_snapshot</TT
>'s textual representation is
    <TT
CLASS="LITERAL"
><TT
CLASS="REPLACEABLE"
><I
>xmin</I
></TT
>:<TT
CLASS="REPLACEABLE"
><I
>xmax</I
></TT
>:<TT
CLASS="REPLACEABLE"
><I
>xip_list</I
></TT
></TT
>.
    For example <TT
CLASS="LITERAL"
>10:20:10,14,15</TT
> means
    <TT
CLASS="LITERAL"
>xmin=10, xmax=20, xip_list=10, 14, 15</TT
>.
   </P
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