m4_comment([$Id: db_get.so,v 10.95 2007/11/07 16:51:38 bostic Exp $])

define(M4PAGELOCAL,
	[dbh_get, dbh_pget, DB_CONSUME, DB_CONSUME_WAIT, DB_GET_BOTH,
	DB_IGNORE_LEASE, DB_MULTIPLE, DB_SET_RECNO])
include(m4/m4.seealso)

m4_pf_header(m4_ref(dbh_get),
ifelse(M4API, C_API, [dnl
int
DB-__GT__get(DB *db,
    DB_TXN *txnid, DBT *key, DBT *data, u_int32_t flags);
m4_blank
int
DB-__GT__pget(DB *db,
    DB_TXN *txnid, DBT *key, DBT *pkey, DBT *data, u_int32_t flags);
])
ifelse(M4API, CXX_API, [dnl
int
Db::get(DbTxn *txnid, Dbt *key, Dbt *data, u_int32_t flags);
m4_blank
int
Db::pget(DbTxn *txnid, Dbt *key, Dbt *pkey, Dbt *data, u_int32_t flags);
]))

m4_p([dnl
The m4_refT(dbh_get) retrieves key/data pairs from the database.  The
address and length of the data associated with the specified m4_arg(key)
are returned in the structure to which m4_arg(data) refers.])

m4_p([dnl
In the presence of duplicate key values, m4_ref(dbh_get) will return the
first data item for the designated key.  Duplicates are sorted by insert
order, except where this order has been overridden by cursor operations.
m4_bold([Retrieval of duplicates requires the use of cursor operations.])
See m4_ref(dbc_get) for details.])

m4_p([dnl
When called on a database that has been made into a secondary index
using the m4_refT(dbh_associate), the m4_ref(dbh_get) and
m4_refT(dbh_pget)s return the key from the secondary index and the data
item from the primary database.  In addition, the m4_refT(dbh_pget)
returns the key from the primary database.  In databases that are not
secondary indices, the m4_refT(dbh_pget) will always fail.])

m4_return(dbh_get,
specific, DB_NOTFOUND, [if the specified key is not in the database],
specific, DB_KEYEMPTY, [if the database is a Queue or Recno database and
the specified key exists, but was never explicitly created by the
application or was later deleted], prev)

m4_parambegin
m4_param_data
m4_param(flags, [dnl
m4_sf_zmust(1)

m4_tagbegin
m4_tag(m4_idef(DB_CONSUME), [dnl
Return the record number and data from the available record closest to
the head of the queue, and delete the record.  The record number will
be returned in m4_arg(key), as described in m4_ref(Dbt).  The data will
be returned in the m4_arg(data) parameter.  A record is available if it
is not deleted and is not currently locked.  The underlying database
must be of type Queue for m4_ref(DB_CONSUME) to be specified.])

m4_tag(m4_idef(DB_CONSUME_WAIT), [dnl
The m4_ref(DB_CONSUME_WAIT) flag is the same as the m4_ref(DB_CONSUME)
flag, except that if the Queue database is empty, the thread of control
will wait until there is data in the queue before returning.  The
underlying database must be of type Queue for m4_ref(DB_CONSUME_WAIT)
to be specified.
m4_p([dnl
If lock or transaction timeouts have been specified, the m4_refT(dbh_get)
with the m4_ref(DB_CONSUME_WAIT) flag
ifelse(M4EXCEPT, except_return, [dnl
may return m4_ref(DB_LOCK_NOTGRANTED) or throw a
m4_ref(DbLockNotGrantedException) exception.],
M4EXCEPT, except_err, [dnl
may throw a m4_ref(DbLockNotGrantedException) exception.],[dnl
may return m4_ref(DB_LOCK_NOTGRANTED).])
This failure, by itself, does not require the enclosing transaction be
aborted.])])

m4_tag(m4_idef(DB_GET_BOTH), [dnl
Retrieve the key/data pair only if both the key and data match the
arguments.
m4_p([dnl
When used with the m4_refT(dbh_pget) version of this method on a
secondary index handle, return the secondary key/primary key/data tuple
only if both the primary and secondary keys match the arguments.  It is
an error to use the m4_ref(DB_GET_BOTH) flag with the m4_ref(dbh_get)
version of this method and a secondary index handle.])])

m4_tag(m4_idef(DB_SET_RECNO), [dnl
Retrieve the specified numbered key/data pair from a database.  Upon
return, both the m4_arg(key) and m4_arg(data) items will have been
filled in.
m4_p([dnl
The m4_arg(data) field of the specified m4_arg(key) must be a pointer
to a logical record number (that is, a m4_arg(db_recno_t)).  This record
number determines the record to be retrieved.])
m4_p([dnl
For m4_ref(DB_SET_RECNO) to be specified, the underlying database must be
of type Btree, and it must have been created with the DB_RECNUM flag.])])
m4_tagend

m4_sf_or_add(1)

m4_tagbegin
m4_tag(m4_idef(DB_IGNORE_LEASE), [dnl
Return the data item irrespective of the state of master leases.  The
item will be returned under all conditions: if master leases are not
configured, if the request is made to a client, if the request is made
to a master with a valid lease, or if the request is made to a master
without a valid lease.])

m4_tag(m4_idef(DB_MULTIPLE), [dnl
Return multiple data items in the buffer to which the m4_arg(data)
parameter refers.
m4_p([dnl
In the case of Btree or Hash databases, all of the data items associated
with the specified key are entered into the buffer.  In the case of
Queue or Recno databases, all of the data items in the database,
starting at, and subsequent to, the specified key, are entered into the
buffer.])
m4_p([dnl
m4_bulk_mem])
m4_p([dnl
The m4_ref(DB_MULTIPLE) flag may only be used alone, or with the
m4_ref(DB_GET_BOTH) and m4_ref(DB_SET_RECNO) options.  The
m4_ref(DB_MULTIPLE) flag may not be used when accessing databases made
into secondary indices using the m4_refT(dbh_associate).])
m4_p([dnl
See
ifelse(M4API, C_API, m4_ref(DB_MULTIPLE_INIT), m4_ref(DbMultipleDataIterator))
for more information.])])

m4_tag(m4_idef(DB_READ_COMMITTED), [dnl
Configure a transactional get operation to have degree 2 isolation (the
read is not repeatable).])

m4_tag(m4_idef(DB_READ_UNCOMMITTED), [dnl
Configure a transactional get operation to have degree 1 isolation,
reading modified but not yet committed data.  Silently ignored if the
m4_ref(DB_READ_UNCOMMITTED) flag was not specified when the underlying
database was opened.])

m4_rmw_flag([Because the m4_refT(dbh_get) will not hold locks across
m4_db calls in non-transactional operations, the m4_ref(DB_RMW) flag
to the m4_ref(dbh_get) call is meaningful only in the presence of
transactions.])

m4_tagend])

m4_param_key
m4_param(pkey, [dnl
The m4_arg(pkey) parameter is the return key from the primary database.])
m4_param_txn(dbh_get)

m4_paramend

m4_err(dbh_get,
buffersmall,
[requested item could not be returned due to undersized buffer],
deadlock,
locknotgranted,
[m4_ref(DB_CONSUME_WAIT) flag was specified, lock or transaction
timers were configured and the],
rephandle, replease, replockout, secondary_bad, einval,
[a record number of 0 was specified;
the m4_ref(DB_THREAD) flag was specified to the m4_refT(dbh_open) and
none of the m4_ref(DB_DBT_MALLOC), m4_ref(DB_DBT_REALLOC) or
m4_ref(DB_DBT_USERMEM) flags were set in the m4_ref(Dbt);
the m4_refT(dbh_pget) was called with a m4_ref(Db) handle that does not
refer to a secondary index])

m4_seealso(Db)
m4_page_footer