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<H2>
<A NAME="Database Commands"></A>Database Commands</H2>
The database commands provide a conduit into the DB method functions.
They are all fairly straightforward and I describe them in terms of their
DB functions briefly here, with a link to the DB page where appropriate.
The first set of commands are those I believe will be the primary functions
used by most databases. Some are directly related to their DB counterparts,
and some are higher level functions that are useful to provide the user.
<P><B>> berkdb open [-env <I>env</I>]</B>
<BR><B> [-btree|-hash|-recno|-queue|-unknown]</B>
<BR><B> [-create] [-excl] [-nommap] [-rdonly] [-truncate]
[-mode
<I>mode</I>] [-errfile <I>filename</I>]</B>
<BR><B> [-dup] [-dupsort] [-recnum] [-renumber] [-revsplitoff]
[-snapshot]</B>
<BR><B> [-extent <I>size</I>]</B>
<BR><B> [-ffactor <I>density</I>]</B>
<BR><B> [-nelem <I>size</I>]</B>
<BR><B> [-lorder <I>order</I>]</B>
<BR><B> [-delim <I>delim</I>]</B>
<BR><B> [-len <I>len</I>]</B>
<BR><B> [-pad <I>pad</I>]</B>
<BR><B> [-source <I>file</I>]</B>
<BR><B> [-minkey <I>minkey</I>]</B>
<BR><B> [-cachesize {<I>gbytes bytes ncaches</I>}]</B>
<BR><B> [-pagesize <I>pagesize</I>]</B>
<BR><B> [--]</B>
<BR><B> [<I>filename </I>[<I>subdbname</I>]]</B>
<P>This command will invoke the <A HREF="../../docs/api_c/db_create.html">db_create</A>
function. If the command is given the <B>-env</B> option, then we
will accordingly creating the database within the context of that environment.
After it successfully gets a handle to a database, we bind it to a new
Tcl command of the form <B><I>dbX, </I></B>where X is an integer starting
at 0 (e.g. <B>db0, db1, </B>etc). We use the <I>Tcl_CreateObjCommand() </I>
to create the top level database function. It is through this handle
that the user can access all of the commands described in the <A HREF="#Database Commands">Database
Commands</A> section. Internally, the database handle is sent as
the <I>ClientData</I> portion of the new command set so that all future
database calls access the appropriate handle.
<P>After parsing all of the optional arguments affecting the setup of the
database and making the appropriate calls to DB to manipulate those values,
we open the database for the user. It translates to the
<A HREF="../../docs/api_c/db_open.html">DB->open</A>
method call after parsing all of the various optional arguments.
We automatically set the DB_THREAD flag. The arguments are:
<UL>
<LI>
<B>-- </B>- Terminate the list of options and use remaining arguments as
the file or subdb names (thus allowing the use of filenames beginning with
a dash '-')</LI>
<LI>
<B>-btree</B> - DB_BTREE database</LI>
<LI>
<B>-hash</B> - DB_HASH database</LI>
<LI>
<B>-recno </B> - DB_RECNO database</LI>
<LI>
<B>-queue</B> - DB_QUEUE database</LI>
<LI>
<B>-create</B> selects the DB_CREATE flag to create underlying files</LI>
<LI>
<B>-excl</B> selects the DB_EXCL flag to exclusively create underlying
files</LI>
<LI>
<B>-nommap</B> selects the DB_NOMMAP flag to forbid mmaping of files</LI>
<LI>
<B>-rdonly</B> selects the DB_RDONLY flag for opening in read-only mode</LI>
<LI>
<B>-truncate</B> selects the DB_TRUNCATE flag to truncate the database</LI>
<LI>
<B>-mode<I> mode</I></B> specifies the mode for created files</LI>
<LI>
<B>-errfile </B>specifies the error file to use for this environment to
<B><I>filename</I></B>
by calling <A HREF="../../docs/api_c/db_set_errfile.html">DB->set_errfile</A><B><I>.
</I></B>If
the file already exists then we will append to the end of the file</LI>
<LI>
<B>-dup </B>selects the DB_DUP flag to permit duplicates in the database</LI>
<LI>
<B>-dupsort</B> selects the DB_DUPSORT flag to support sorted duplicates</LI>
<LI>
<B>-recnum</B> selects the DB_RECNUM flag to support record numbers in
btrees</LI>
<LI>
<B>-renumber </B>selects the DB_RENUMBER flag to support mutable record
numbers</LI>
<LI>
<B>-revsplitoff </B>selects the DB_REVSPLITOFF flag to suppress reverse
splitting of pages on deletion</LI>
<LI>
<B>-snapshot </B>selects the DB_SNAPSHOT flag to support database snapshots</LI>
<LI>
<B>-extent </B>sets the size of a Queue database extent to the given <B><I>size
</I></B>using
the <A HREF="../../docs/api_c/db_set_q_extentsize.html">DB->set_q_extentsize</A>
method</LI>
<LI>
<B>-ffactor</B> sets the hash table key density to the given <B><I>density
</I></B>using
the <A HREF="../../docs/api_c/db_set_h_ffactor.html">DB->set_h_ffactor</A>
method</LI>
<LI>
<B>-nelem </B>sets the hash table size estimate to the given <B><I>size
</I></B>using
the <A HREF="../../docs/api_c/db_set_h_nelem.html">DB->set_h_nelem</A>
method</LI>
<LI>
<B>-lorder </B>sets the byte order for integers stored in the database
meta-data to the given <B><I>order</I></B> using the <A HREF="../../docs/api_c/db_set_lorder.html">DB->set_lorder</A>
method</LI>
<LI>
<B>-delim </B>sets the delimiting byte for variable length records to
<B><I>delim</I></B>
using the <A HREF="../../docs/api_c/db_set_re_delim.html">DB->set_re_delim</A>
method</LI>
<LI>
<B>-len </B>sets the length of fixed-length records to <B><I>len</I></B>
using the <A HREF="../../docs/api_c/db_set_re_len.html">DB->set_re_len</A>
method</LI>
<LI>
<B>-pad </B>sets the pad character used for fixed length records to
<B><I>pad</I></B>
using the <A HREF="../../docs/db_set_re_pad.html">DB->set_re_pad</A> method</LI>
<LI>
<B>-source </B>sets the backing source file name to <B><I>file</I></B>
using the <A HREF="../../docs/api_c/db_set_re_source.html">DB->set_re_source</A>
method</LI>
<LI>
<B>-minkey </B>sets the minimum number of keys per Btree page to <B><I>minkey</I></B>
using the <A HREF="../../docs/api_c/db_set_bt_minkey.html">DB->set_bt_minkey</A>
method</LI>
<LI>
<B>-cachesize </B>sets the size of the database cache to the size
specified by <B><I>gbytes </I></B>and <B><I>bytes, </I></B>broken up into
<B><I>ncaches</I></B>
number of caches using the <A HREF="../../docs/api_c/db_set_cachesize.html">DB->set_cachesize</A>
method</LI>
<LI>
<B>-pagesize </B>sets the size of the database page to <B><I>pagesize </I></B>using
the <A HREF="../../docs/api_c/db_set_pagesize.html">DB->set_pagesize</A>
method</LI>
<LI>
<B><I>filename</I></B> indicates the name of the database</LI>
<LI>
<B><I>subdbname</I></B> indicate the name of the sub-database</LI>
</UL>
<HR WIDTH="100%">
<BR><B> berkdb upgrade [-dupsort] [-env <I>env</I>] [--] [<I>filename</I>]</B>
<P>This command will invoke the <A HREF="../../docs/api_c/db_upgrade.html">DB->upgrade</A>
function. If the command is given the <B>-env</B> option, then we
will accordingly upgrade the database filename within the context of that
environment. The <B>-dupsort</B> option selects the DB_DUPSORT flag for
upgrading. The use of --<B> </B>terminates the list of options, thus allowing
filenames beginning with a dash.
<P>
<HR WIDTH="100%"><B>> berkdb verify [-env <I>env</I>] [--] [<I>filename</I>]</B>
<P>This command will invoke the <A HREF="../../docs/api_c/db_verify.html">DB->verify</A>
function. If the command is given the <B>-env</B> option, then we
will accordingly verify the database filename within the context of that
environment. The use of --<B> </B>terminates the list of options,
thus allowing filenames beginning with a dash.
<P>
<HR WIDTH="100%"><B>> <I>db</I> join [-nosort] <I>db0.c0 db1.c0</I> ...</B>
<P>This command will invoke the <A HREF="../../docs/api_c/db_join.html">db_join</A>
function. After it successfully joins a database, we bind it to a
new Tcl command of the form <B><I>dbN.cX, </I></B>where X is an integer
starting at 0 (e.g. <B>db2.c0, db3.c0, </B>etc). We use the <I>Tcl_CreateObjCommand() </I>
to create the top level database function. It is through this cursor
handle that the user can access the joined data items.
<P>The options are:
<UL>
<LI>
<B>-nosort -</B> This flag causes DB not to sort the cursors based on the
number of data items they reference. It results in the DB_JOIN_NOSORT
flag being set.</LI>
</UL>
<HR WIDTH="100%"><B>> <I>db</I> get_join [-nosort] {db key} {db key} ...</B>
<P>This command performs a join operation on the keys specified and returns
a list of the joined {key data} pairs.
<P>The options are:
<UL>
<LI>
<B>-nosort</B> This flag causes DB not to sort the cursors based on the
number of data items they reference. It results in the DB_JOIN_NOSORT
flag being set.</LI>
</UL>
<HR WIDTH="100%"><B>> <I>db</I> keyrange [-txn <I>id</I>] key</B>
<P>This command returns the range for the given <B>key</B>. It returns
a list of 3 double elements of the form {<B><I>less equal greater</I></B>}
where <B><I>less</I></B> is the percentage of keys less than the given
key, <B><I>equal</I></B> is the percentage equal to the given key and <B><I>greater</I></B>
is the percentage greater than the given key. If the -txn option
is specified it performs this operation under transaction protection.
<BR>
<HR WIDTH="100%"><B>> <I>db</I> put</B>
<P>The <B>undocumented</B> options are:
<UL>
<LI>
<B>-nodupdata</B> This flag causes DB not to insert the key/data pair if
it already exists, that is, both the key and data items are already in
the database. The -nodupdata flag may only be specified if the underlying
database has been configured to support sorted duplicates.</LI>
</UL>
<HR WIDTH="100%"><B>> <I>db</I> stat</B>
<P>The <B>undocumented</B> options are:
<UL>
<LI>
<B>-cachedcounts</B> This flag causes DB to return the cached key/record
counts, similar to the DB_CACHED_COUNTS flags to DB->stat.</LI>
</UL>
<HR WIDTH="100%"><B>> <I>dbc</I> put</B>
<P>The <B>undocumented</B> options are:
<UL>
<LI>
<B>-nodupdata</B> This flag causes DB not to insert the key/data pair if
it already exists, that is, both the key and data items are already in
the database. The -nodupdata flag may only be specified if the underlying
database has been configured to support sorted duplicates.</LI>
</UL>
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