Database Reference
In-Depth Information
a
c
d
Atomicity:
Transactions
are all or
nothing
Consistency:
Only valid data
is saved
Isolation:
Transactions
do not affect
each other
Durability:
Written data
will not be lost
•
Atomicity
: This means that changes in the database must follow an
all
or nothing
rule. Transactions are said to be "atomic" if one part of the
transaction fails, then the consequence would be that the entire transaction
is rolled back.
•
Consistency
: This means that only consistent or "valid" data will be allowed to
be entered into the database. In relational terminology, this often means that
the
schema
of the database has to be applied and maintained at all times. The
main consistency requirement in Neo4j is actually that the graph relationships
must have a start and an end node. Relationships cannot be dangling. Aside
from this, however, the consistency rules in Neo4j will obviously be much
looser, as Neo4j implements the concept of an "optional" schema.
The optional schema of Neo4j is really interesting: the idea being that it
is actually incredibly useful to have a schema-free database when you
are still at the beginning of your development cycles. As you are refining
your knowledge about the domain and its requirements, your data
model will just grow with you—free of any requirements to pre-impose
a schema on your iterations. However, as you move closer to production,
schema—and therefore consistency—can be really useful. At that point,
system administrators and business owners alike will want to have
more checks and balances around data quality, and the C in ACID will
become more important. Neo4j fully supports both approaches, which is
tremendously useful in today's agile development methodologies.
