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<h1>DB->key_range</h1>
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<h3><pre>
#include <db.h>
<p>
int
DB->key_range(DB *db, DB_TXN *txnid,
DBT *key, DB_KEY_RANGE *key_range, u_int32_t flags);
</pre></h3>
<h1>Description</h1>
<p>The DB->key_range function returns an estimate of the proportion of keys
that are less than, equal to and greater than the specified key. The
underlying database must be of type Btree.
<p>The information is returned in the <b>key_range</b> argument, which
contains three elements of type double, <b>less</b>, <b>equal</b> and
<b>greater</b>. Values are in the range of 0 to 1, e.g., if the field
<b>less</b> is 0.05, that indicates that 5% of the keys in the database
are less than the key argument. The value for <b>equal</b> will be zero
if there is no matching key and non-zero otherwise.
<p>If the file is being accessed under transaction protection, the
<b>txnid</b> parameter is a transaction ID returned from
<a href="../api_c/txn_begin.html">txn_begin</a>, otherwise, NULL.
The DB->key_range function does not retain the locks it acquires for the
life of the transaction, so estimates may not be repeatable.
<p>The <b>flags</b> parameter is currently unused, and must be set to 0.
<p>The DB->key_range function returns a non-zero error value on failure and 0 on success.
<h1>Errors</h1>
<p>The DB->key_range function may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>DB_LOCK_DEADLOCK<dd>The operation was selected to resolve a deadlock.
</dl>
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
<p>The underlying database was not of type Btree.
</dl>
<p>The DB->key_range function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB->key_range function may fail and return
<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
in the same way.
<h1>See Also</h1>
<a href="../api_c/db_create.html">db_create</a>,
<a href="../api_c/db_close.html">DB->close</a>,
<a href="../api_c/db_cursor.html">DB->cursor</a>,
<a href="../api_c/db_del.html">DB->del</a>,
<a href="../api_c/db_err.html">DB->err</a>,
<a href="../api_c/db_fd.html">DB->fd</a>,
<a href="../api_c/db_get.html">DB->get</a>,
<a href="../api_c/db_get_byteswapped.html">DB->get_byteswapped</a>,
<a href="../api_c/db_get_type.html">DB->get_type</a>,
<a href="../api_c/db_join.html">DB->join</a>,
<a href="../api_c/db_key_range.html">DB->key_range</a>,
<a href="../api_c/db_open.html">DB->open</a>,
<a href="../api_c/db_put.html">DB->put</a>,
<a href="../api_c/db_remove.html">DB->remove</a>,
<a href="../api_c/db_set_bt_compare.html">DB->set_bt_compare</a>,
<a href="../api_c/db_set_bt_minkey.html">DB->set_bt_minkey</a>,
<a href="../api_c/db_set_bt_prefix.html">DB->set_bt_prefix</a>,
<a href="../api_c/db_set_cachesize.html">DB->set_cachesize</a>,
<a href="../api_c/db_set_dup_compare.html">DB->set_dup_compare</a>,
<a href="../api_c/db_set_errcall.html">DB->set_errcall</a>,
<a href="../api_c/db_set_errfile.html">DB->set_errfile</a>,
<a href="../api_c/db_set_errpfx.html">DB->set_errpfx</a>,
<a href="../api_c/db_set_flags.html">DB->set_flags</a>,
<a href="../api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a>,
<a href="../api_c/db_set_h_hash.html">DB->set_h_hash</a>,
<a href="../api_c/db_set_h_nelem.html">DB->set_h_nelem</a>,
<a href="../api_c/db_set_lorder.html">DB->set_lorder</a>,
<a href="../api_c/db_set_malloc.html">DB->set_malloc</a>,
<a href="../api_c/db_set_pagesize.html">DB->set_pagesize</a>,
<a href="../api_c/db_set_paniccall.html">DB->set_paniccall</a>,
<a href="../api_c/db_set_q_extentsize.html">DB->set_q_extentsize</a>,
<a href="../api_c/db_set_realloc.html">DB->set_realloc</a>,
<a href="../api_c/db_set_re_delim.html">DB->set_re_delim</a>,
<a href="../api_c/db_set_re_len.html">DB->set_re_len</a>,
<a href="../api_c/db_set_re_pad.html">DB->set_re_pad</a>,
<a href="../api_c/db_set_re_source.html">DB->set_re_source</a>,
<a href="../api_c/db_stat.html">DB->stat</a>,
<a href="../api_c/db_sync.html">DB->sync</a>,
<a href="../api_c/db_upgrade.html">DB->upgrade</a>
and
<a href="../api_c/db_verify.html">DB->verify</a>.
</tt>
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