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2023-12-01

DB(dbEnv=None, flags=0)

Constructor.

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append(data, txn=None)

A convenient version of put() that can be used for

Recno or Queue databases. The DB_APPEND flag is

automatically used, and the record number is

returned.

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associate(secondaryDB, callback, flags=0)

Used to associate secondaryDB to act as a secondary

index for this (primary) database. The callback

parameter should be a reference to a Python callable

object that will consruct and return the secondary key

or DB_DONOTINDEX if the item should not be indexed.

The parameters the callback will receive are the

primaryKey and primaryData values.

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close(flags=0)

Flushes cached data and closes the database

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consume(txn=None, flags=0)

For a database with the Queue access method, returns

the record number and data from the first available

record and deletes it from the queue.

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consume_wait(txn=None, flags=0)

For a database with the Queue access method, returns

the record number and data from the first available

record and deletes it from the queue. If the Queue

database is empty, the thread of control will wait

until there is data in the queue before returning.

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cursor(txn=None, flags=0)

Create a cursor on the DB and returns a DBCursor

object. If a transaction is passed then the cursor

can only be used within that transaction and you

must be sure to close the cursor before commiting

the transaction.

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delete(key, txn=None, flags=0)

Removes a key/data pair from the database

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fd()

Returns a file descriptor for the database

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get(key, default=None, txn=None, flags=0, dlen=-1, doff=-1)

Returns the data object associated with key. If key

is an integer then the DB_SET_RECNO flag is

automatically set for BTree databases and the actual

key and the data value are returned as a tuple. If

default is given then it is returned if the key is not

found in the database. Partial records can be read

using dlen and doff, however be sure to not read

beyond the end of the actual data or you may get

garbage.

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get_both(key, data, txn=None, flags=0)

A convenient version of get() that automatically sets

the DB_GET_BOTH flag, and which will be successful

only if both the key and data value are found in the

database. (Can be used to verify the presence of a

record in the database when duplicate keys are

allowed.)

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get_byteswapped()

May be used to determine if the database was created

on a machine with the same endianess as the current

machine.

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get_size(key, txn=None)

Return the size of the data object associated with key.

get_type()

Return the database's access method type

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join(cursorList, flags=0)

Create and return a specialized cursor for use in

performing joins on secondary indices

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key_range(key, txn=None, flags=0)

Returns an estimate of the proportion of keys that are

less than, equal to and greater than the specified key.

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open(filename, dbname=None, dbtype=DB_UNKNOWN, flags=0, mode=0660)

Opens the database named dbname in the file named

fileName. The dbname argument is optional and allows

applications to have multiple logical databases in a

single physical file. It is an error to attempt to

open a second database in a file that was not

initially created using a database name. In-memory

databases never intended to be shared or preserved on

disk may be created by setting both the fileName and

dbName arguments to None.

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put(key, data, txn=None, flags=0, dlen=-1, doff=-1)

Stores the key/data pair in the database. If the

DB_APPEND flag is used and the database is using the

Recno or Queue access method then the record number

allocated to the data is returned. Partial data

objects can be written using dlen and doff.

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remove(filename, dbname=None, flags=0)

Remove a database

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rename(filename, dbname, newname, flags=0)

Rename a database

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set_bt_compare(compareFunc)

Set the B-Tree database comparison function. This

can only be called once before the database has

been opened. compareFunc takes two arguments:

(left key string, right key string)

It must return a -1, 0, 1 integer similar to cmp.

You can shoot your database in the foot, beware!

Read the BerkeleyDB docs for the full details of

how the comparison function MUST behave.

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set_bt_minkey(minKeys)

Set the minimum number of keys that will be stored on

any single BTree page

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set_cachesize(gbytes, bytes, ncache=0)

Set the size of the database's shared memory buffer pool

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set_get_returns_none(flag):

Controls what get and related methods do when a key is

not found.

See the DBEnv set_get_returns_none documentation.

The previous setting is returned.

set_flags(flags)

Set additional flags on the database before opening.

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set_h_ffactor(ffactor)

Set the desired density within the hash table

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set_h_nelem(nelem)

Set an estimate of the final size of the hash table

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set_lorder(lorder)

Set the byte order for integers in the stored database

metadata.

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set_pagesize(pagesize)

Set the size of the pages used to hold items in the

database, in bytes.

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set_re_delim(delim)

Set the delimiting byte used to mark the end of a

record in the backing source file for the Recno access

method.

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set_re_len(length)

For the Queue access method, specify that the records

are of length length. For the Recno access method,

specify that the records are fixed-length, not byte

delimited, and are of length length.

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set_re_pad(pad)

Set the padding character for short, fixed-length

records for the Queue and Recno access methods.

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set_re_source(source)

Set the underlying source file for the Recno access method

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set_q_extentsize(extentsize)

Set the size of the extents used to hold pages in a

Queue database, specified as a number of pages. Each

extent is created as a separate physical file. If no

extent size is set, the default behavior is to create

only a single underlying database file.

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stat(flags=0)

Return a dictionary containing database

statistics with the following keys.

For Hash databases:

magic

Magic number that identifies the file as a Hash

database.

version

Version of the Hash database.

nkeys

Number of unique keys in the database.

ndata

Number of key/data pairs in the database.

pagesize

Underlying Hash database page (& bucket) size.

nelem

Estimated size of the hash table specified at

database creation time.

ffactor

Desired fill factor (number of items per bucket)

specified at database creation time.

buckets

Number of hash buckets.

free

Number of pages on the free list.

bfree

Number of bytes free on bucket pages.

bigpages

Number of big key/data pages.

big_bfree

Number of bytes free on big item pages.

overflows

Number of overflow pages (overflow pages are

pages that contain items that did not fit in

the main bucket page).

ovfl_free

Number of bytes free on overflow pages.

dup

Number of duplicate pages.

dup_free

Number of bytes free on duplicate pages.

For BTree and Recno databases:

magic

Magic number that identifies the file as a

Btree database.

version

Version of the Btree database.

nkeys

For the Btree Access Method, the number of

unique keys in the database.

For the Recno Access Method, the number of

records in the database. If the database has

been configured to not re-number records

during deletion, the number of records may

include records that have been deleted.

ndata

For the Btree Access Method, the number of

key/data pairs in the database,

For the Recno Access Method, the number of

records in the database. If the database has

been configured to not re-number records

during deletion, the number of records may

include records that have been deleted.

pagesize

Underlying database page size.

minkey

Minimum keys per page.

re_len

Length of fixed-length records.

re_pad

Padding byte value for fixed-length records.

levels

Number of levels in the database.

int_pg

Number of database internal pages.

leaf_pg

Number of database leaf pages.

dup_pg

Number of database duplicate pages.

over_pg

Number of database overflow pages.

free

Number of pages on the free list.

int_pgfree

Num of bytes free in database internal pages.

leaf_pgfree

Number of bytes free in database leaf pages.

dup_pgfree

Num bytes free in database duplicate pages.

over_pgfree

Num of bytes free in database overflow pages.

For Queue databases:

magic

Magic number that identifies the file as a

Queue database.

version

Version of the Queue file type.

nkeys

Number of records in the database.

ndata

Number of records in the database.

pagesize

Underlying database page size.

pages

Number of pages in the database.

re_len

Length of the records.

re_pad

Padding byte value for the records.

pgfree

Number of bytes free in database pages.

start

Start offset.

first_recno

First undeleted record in the database.

cur_recno

Last allocated record number in the database.

sync(flags=0)

Flushes any cached information to disk

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truncate(txn=None, flags=0)

Empties the database, discarding all records it

contains. The number of records discarded from the

database is returned.

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upgrade(filename, flags=0)

Upgrades all of the databases included in the file

filename, if necessary.

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verify(filename, dbname=None, outfile=None, flags=0)

Verifies the integrity of all databases in the file

specified by the filename argument, and optionally

outputs the databases' key/data pairs to a file.

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