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<!--$Id: db_stat.so,v 10.48 2001/05/05 01:49:12 bostic Exp $-->
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<title>Berkeley DB: DB->stat</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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<table width="100%"><tr valign=top>
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a>
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DB->stat(DB *db, void *sp, u_int32_t flags);
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<p>The DB->stat function creates a statistical structure and
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copies a pointer to it into user-specified memory locations.
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Specifically, if <b>sp</b> is non-NULL, a pointer to the statistics
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for the database are copied into the memory location to which it refers.
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<p>Statistical structures are created in allocated memory. If application-specific allocation
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routines have been declared (see <a href="../api_c/env_set_alloc.html">DB_ENV->set_alloc</a> for more
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information), they are used to allocate the memory; otherwise, the
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library function <b>malloc</b>(3) is used. The caller is
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responsible for deallocating the memory. To deallocate the memory, free
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the memory reference; references inside the returned memory need not be
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<p>The <b>flags</b> value must be set to 0 or
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one of the following values:
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<p><dt><a name="DB_CACHED_COUNTS">DB_CACHED_COUNTS</a><dd>Return a cached count of the keys and records in a database.
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<b>The DB_CACHED_COUNTS flag has been deprecated in
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favor of the DB_FAST_STAT flag. Please update your
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<p><dt><a name="DB_FAST_STAT">DB_FAST_STAT</a><dd>Return only the values which do not require traversal of the database.
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Fields returned when this flag is set are noted with an asterisk (*)
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<p>Among other things, this flag makes it possible for applications to
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request key and record counts without incurring the performance penalty
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of traversing the entire database. If the underlying database is of
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type Recno, or of type Btree and the database was created with the
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<a href="../api_c/db_set_flags.html#DB_RECNUM">DB_RECNUM</a> flag, the count of keys will be exact. Otherwise,
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the count of keys will be the value saved the last time the database
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was traversed, or 0 if no count of keys has ever been made. If the
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underlying database is of type Recno, the count of data items will be
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exact, otherwise, the count of data items will be the value saved the
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last time the database was traversed, or 0 if no count of data items
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<p><dt><a name="DB_RECORDCOUNT">DB_RECORDCOUNT</a><dd>Return a count of the records in a Btree or Recno Access Method
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database. <b>The DB_RECORDCOUNT flag has been
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deprecated in favor of the DB_FAST_STAT flag. Please update
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your applications.</b>
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<p>If the DB_FAST_STAT flag has not been specified, the
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DB->stat function will access some of or all the pages in the database,
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incurring a severe performance penalty as well as possibly flushing the
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underlying buffer pool.
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<p>In the presence of multiple threads or processes accessing an active
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database, the information returned by DB->stat may be out-of-date.
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<p>If the database was not opened read-only and the DB_FAST_STAT
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flag was not specified, the cached key and record numbers will be
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updated after the statistical information has been gathered.
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<p>The DB->stat function cannot be transaction-protected. For this reason,
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it should be called in a thread of control that has no open cursors or
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<p>The DB->stat function returns a non-zero error value on failure and 0 on success.
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<h3>Hash Statistics</h3>
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<p>In the case of a Hash database,
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the statistics are stored in a structure of type DB_HASH_STAT. The
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following fields will be filled in:
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<p><dt>u_int32_t hash_magic*<dd>Magic number that identifies the file as a Hash file.
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<dt>u_int32_t hash_version*<dd>The version of the Hash database.
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<dt>u_int32_t hash_nkeys*<dd>The number of unique keys in the database. If DB_FAST_STAT was
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specified the count will be the last saved value unless it has never
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been calculated, in which case it will be 0.
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<dt>u_int32_t hash_ndata*<dd>The number of key/data pairs in the database. If DB_FAST_STAT
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was specified the count will be the last saved value unless it has never
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been calculated, in which case it will be 0.
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<dt>u_int32_t hash_pagesize*<dd>The underlying Hash database page (and bucket) size, in bytes.
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<dt>u_int32_t hash_nelem*<dd>The estimated size of the hash table specified at database-creation time.
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<dt>u_int32_t hash_ffactor*<dd>The desired fill factor (number of items per bucket) specified at
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database-creation time.
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<dt>u_int32_t hash_buckets*<dd>The number of hash buckets.
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<dt>u_int32_t hash_free<dd>The number of pages on the free list.
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<dt>u_int32_t hash_bfree<dd>The number of bytes free on bucket pages.
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<dt>u_int32_t hash_bigpages<dd>The number of big key/data pages.
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<dt>u_int32_t hash_big_bfree<dd>The number of bytes free on big item pages.
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<dt>u_int32_t hash_overflows<dd>The number of overflow pages (overflow pages are pages that contain items
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that did not fit in the main bucket page).
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<dt>u_int32_t hash_ovfl_free<dd>The number of bytes free on overflow pages.
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<dt>u_int32_t hash_dup<dd>The number of duplicate pages.
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<dt>u_int32_t hash_dup_free<dd>The number of bytes free on duplicate pages.
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<h3>Btree and Recno Statistics</h3>
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<p>In the case of a Btree or Recno database,
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the statistics are stored in a structure of type DB_BTREE_STAT. The
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following fields will be filled in:
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<p><dt>u_int32_t bt_magic*<dd>Magic number that identifies the file as a Btree database.
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<dt>u_int32_t bt_version*<dd>The version of the Btree database.
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<dt>u_int32_t bt_nkeys*<dd>For the Btree Access Method, the number of unique keys in the database.
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If DB_FAST_STAT was specified and the database was created with
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the <a href="../api_c/db_set_flags.html#DB_RECNUM">DB_RECNUM</a> flag, the count will be exact, otherwise, the
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count will be the last saved value unless it has never been calculated,
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in which case it will be 0.
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<p>For the Recno Access Method, the exact number of records in the
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<dt>u_int32_t bt_ndata*<dd>For the Btree Access Method, the number of key/data pairs in the
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database. If DB_FAST_STAT was specified the count will be the
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last saved value unless it has never been calculated, in which case it
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<p>For the Recno Access Method, the exact number of records in the
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database. If the database has been configured to not renumber records
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during deletion, the count of records will only reflect undeleted
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<dt>u_int32_t bt_pagesize*<dd>Underlying database page size, in bytes.
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<dt>u_int32_t bt_minkey*<dd>The minimum keys per page.
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<dt>u_int32_t bt_re_len*<dd>The length of fixed-length records.
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<dt>u_int32_t bt_re_pad*<dd>The padding byte value for fixed-length records.
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<dt>u_int32_t bt_levels<dd>Number of levels in the database.
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<dt>u_int32_t bt_int_pg<dd>Number of database internal pages.
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<dt>u_int32_t bt_leaf_pg<dd>Number of database leaf pages.
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<dt>u_int32_t bt_dup_pg<dd>Number of database duplicate pages.
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<dt>u_int32_t bt_over_pg<dd>Number of database overflow pages.
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<dt>u_int32_t bt_free<dd>Number of pages on the free list.
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<dt>u_int32_t bt_int_pgfree<dd>Number of bytes free in database internal pages.
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<dt>u_int32_t bt_leaf_pgfree<dd>Number of bytes free in database leaf pages.
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<dt>u_int32_t bt_dup_pgfree<dd>Number of bytes free in database duplicate pages.
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<dt>u_int32_t bt_over_pgfree<dd>Number of bytes free in database overflow pages.
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<h3>Queue Statistics</h3>
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<p>In the case of a Queue database,
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the statistics are stored in a structure of type DB_QUEUE_STAT. The
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following fields will be filled in:
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<p><dt>u_int32_t qs_magic*<dd>Magic number that identifies the file as a Queue file.
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<dt>u_int32_t qs_version*<dd>The version of the Queue file type.
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<dt>u_int32_t qs_nkeys*<dd>The number of records in the database. If DB_FAST_STAT was
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specified the count will be the last saved value unless it has never
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been calculated, in which case it will be 0.
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<dt>u_int32_t qs_ndata*<dd>The number of records in the database. If DB_FAST_STAT was
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specified the count will be the last saved value unless it has never
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been calculated, in which case it will be 0.
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<dt>u_int32_t qs_pagesize*<dd>Underlying database page size, in bytes.
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<dt>u_int32_t qs_extentsize*<dd>Underlying database extent size, in pages.
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<dt>u_int32_t qs_pages<dd>Number of pages in the database.
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<dt>u_int32_t qs_re_len*<dd>The length of the records.
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<dt>u_int32_t qs_re_pad*<dd>The padding byte value for the records.
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<dt>u_int32_t qs_pgfree<dd>Number of bytes free in database pages.
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<dt>u_int32_t qs_start<dd>Start offset.
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<dt>u_int32_t qs_first_recno*<dd>First undeleted record in the database.
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<dt>u_int32_t qs_cur_recno*<dd>Last allocated record number in the database.
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<p>The DB->stat function returns a non-zero error value on failure and 0 on success.
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<p>The DB->stat function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
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If a catastrophic error has occurred, the DB->stat function may fail and return
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<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
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<a href="../api_c/db_create.html">db_create</a>,
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<a href="../api_c/db_associate.html">DB->associate</a>,
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<a href="../api_c/db_close.html">DB->close</a>,
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<a href="../api_c/db_cursor.html">DB->cursor</a>,
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<a href="../api_c/db_del.html">DB->del</a>,
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<a href="../api_c/db_err.html">DB->err</a>, <a href="../api_c/db_err.html">DB->errx</a>
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<a href="../api_c/db_fd.html">DB->fd</a>,
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<a href="../api_c/db_get.html">DB->get</a>,
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<a href="../api_c/db_get.html">DB->pget</a>,
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<a href="../api_c/db_get_byteswapped.html">DB->get_byteswapped</a>,
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<a href="../api_c/db_get_type.html">DB->get_type</a>,
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<a href="../api_c/db_join.html">DB->join</a>,
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<a href="../api_c/db_key_range.html">DB->key_range</a>,
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<a href="../api_c/db_open.html">DB->open</a>,
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<a href="../api_c/db_put.html">DB->put</a>,
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<a href="../api_c/db_remove.html">DB->remove</a>,
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<a href="../api_c/db_rename.html">DB->rename</a>,
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<a href="../api_c/db_set_alloc.html">DB->set_alloc</a>,
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<a href="../api_c/db_set_append_recno.html">DB->set_append_recno</a>,
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<a href="../api_c/db_set_bt_compare.html">DB->set_bt_compare</a>,
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<a href="../api_c/db_set_bt_minkey.html">DB->set_bt_minkey</a>,
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<a href="../api_c/db_set_bt_prefix.html">DB->set_bt_prefix</a>,
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<a href="../api_c/db_set_cachesize.html">DB->set_cachesize</a>,
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<a href="../api_c/db_set_dup_compare.html">DB->set_dup_compare</a>,
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<a href="../api_c/db_set_errcall.html">DB->set_errcall</a>,
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<a href="../api_c/db_set_errfile.html">DB->set_errfile</a>,
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<a href="../api_c/db_set_errpfx.html">DB->set_errpfx</a>,
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<a href="../api_c/db_set_feedback.html">DB->set_feedback</a>,
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<a href="../api_c/db_set_flags.html">DB->set_flags</a>,
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<a href="../api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a>,
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<a href="../api_c/db_set_h_hash.html">DB->set_h_hash</a>,
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<a href="../api_c/db_set_h_nelem.html">DB->set_h_nelem</a>,
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<a href="../api_c/db_set_lorder.html">DB->set_lorder</a>,
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<a href="../api_c/db_set_pagesize.html">DB->set_pagesize</a>,
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<a href="../api_c/db_set_paniccall.html">DB->set_paniccall</a>,
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<a href="../api_c/db_set_q_extentsize.html">DB->set_q_extentsize</a>,
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<a href="../api_c/db_set_re_delim.html">DB->set_re_delim</a>,
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<a href="../api_c/db_set_re_len.html">DB->set_re_len</a>,
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<a href="../api_c/db_set_re_pad.html">DB->set_re_pad</a>,
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<a href="../api_c/db_set_re_source.html">DB->set_re_source</a>,
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<a href="../api_c/db_stat.html">DB->stat</a>,
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<a href="../api_c/db_sync.html">DB->sync</a>,
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<a href="../api_c/db_truncate.html">DB->truncate</a>,
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<a href="../api_c/db_upgrade.html">DB->upgrade</a>,
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<a href="../api_c/db_verify.html">DB->verify</a>.
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