Detailed Description

Datastore transaction support.

Implements sqlite3 transactions on a Datastore. A transaction is a set of reads and updates that should either ALL be done, or NONE at all. Transactions also speed up the script, sometimes by as much of a factor of 300, by grouping I/O operations to the database into one large chunk. However, one must be careful in using them since it keeps the database locked for an extended period of time.

This class should not be used directly. Instead, one should do this to a Datum (Task or Product) object:

with datum_object.transaction() as t: ... do things to the datum object ... transaction is now complete, database is updated.

Definition at line 270 of file datastore.py.

Inheritance diagram for produtil.datastore.Transaction:

Public Member Functions
def	__init__ (self, ds)
	Transaction constructor. More...

def	__enter__ (self)
	Locks the database for the current thread, if it isn't already locked. More...

def	__exit__ (self, etype, evalue, traceback)
	Releases the database lock if this is the last Transaction released for the current thread. More...

def	query
	Performs an SQL query returning the result of cursor.fetchall() More...

def	mutate
	Performs an SQL database modification, returning the result of cursor.lastrowid. More...

def	init_datum
	Add a Datum to the database if it is not there already. More...

def	update_datum (self, d)
	Update database availability and location records. More...

def	refresh_meta
	Replace Datum metadata with database values, add new metadata to database. More...

def	set_meta (self, d, k, v)
	Sets metadata key k to value v for the given Datum. More...

def	del_meta (self, d, k)
	Delete metadata from the database. More...

	ds
	The Datastore containing the database for which this is a transaction.

Public Attributes
	ds

Constructor & Destructor Documentation

def produtil.datastore.Transaction.__init__	(	self,
		ds
	)

Transaction constructor.

Creates the Transaction object but does NOT initiate the transaction.

Definition at line 287 of file datastore.py.

Member Function Documentation

def produtil.datastore.Transaction.__enter__ ( self )

Locks the database for the current thread, if it isn't already locked.

Definition at line 294 of file datastore.py.

def produtil.datastore.Transaction.__exit__	(	self,
		etype,
		evalue,
		traceback
	)

Releases the database lock if this is the last Transaction released for the current thread.

Parameters

etype,evalue	Exception type and value, if any.
traceback	Exception traceback, if any.

Definition at line 303 of file datastore.py.

def produtil.datastore.Transaction.del_meta	(	self,
		d,
		k
	)

Delete metadata from the database.

Deletes the specified metadata key k, which must not be "location" or "available".

Parameters

d	The Datum whose metadata is being deleted.
k	The metadata key, which cannot be "available" or "location".

Definition at line 410 of file datastore.py.

def produtil.datastore.Transaction.init_datum	(	self,
		d,
		meta = `True`
	)

Add a Datum to the database if it is not there already.

Given a Datum, add the object to the database if it is not there already and fill the object with data from the database.

Parameters

d	the Datum
meta	If True, also initialize metadata.

Definition at line 327 of file datastore.py.

Referenced by produtil.datastore.Transaction.refresh_meta().

def produtil.datastore.Transaction.mutate	(	self,
		stmt,
		subvals = `()`
	)

Performs an SQL database modification, returning the result of cursor.lastrowid.

Parameters

stmt	the SQL query
subvals	the substitution values

Definition at line 320 of file datastore.py.

Referenced by produtil.datastore.Transaction.del_meta(), produtil.datastore.Transaction.init_datum(), produtil.datastore.Transaction.set_meta(), and produtil.datastore.Transaction.update_datum().

def produtil.datastore.Transaction.query	(	self,
		stmt,
		subvals = `()`
	)

Performs an SQL query returning the result of cursor.fetchall()

Parameters

stmt	the SQL query
subvals	the substitution values

Definition at line 314 of file datastore.py.

Referenced by produtil.datastore.Transaction.init_datum(), and produtil.datastore.Transaction.refresh_meta().

def produtil.datastore.Transaction.refresh_meta	(	self,
		d,
		or_add = `True`
	)

Replace Datum metadata with database values, add new metadata to database.

Given a Datum d, discards and replaces d._meta with the current metadata, location and availability. Will raise an exception if the product does not exist in the database.

Parameters

d	The Datum.
or_add	If True, then any metadata that does not exist in the database is created from values in d.

Definition at line 368 of file datastore.py.

Referenced by produtil.datastore.Transaction.init_datum().

def produtil.datastore.Transaction.set_meta	(	self,
		d,
		k,
		v
	)

Sets metadata key k to value v for the given Datum.

Modifies the database entries for key k and datum d to have the value v. If k is location or available, then the product table will be updated instead.

Parameters

d	The Datum
k	The metadata key.
v	The value, a string.

Definition at line 395 of file datastore.py.

def produtil.datastore.Transaction.update_datum	(	self,
		d
	)

Update database availability and location records.

Given a Datum whose location and availability is set, update that information in the database, adding the Datum if necessary.

Parameters

d the Datum

Definition at line 357 of file datastore.py.

The documentation for this class was generated from the following file:

/mnt/pan2/projects/hwrfv3/Samuel.Trahan/trunk/ush/produtil/datastore.py

Detailed Description

Public Member Functions

Public Attributes

Constructor & Destructor Documentation

Member Function Documentation