During the export, a graph of the entities is created in the database. Three tables are created for this purpose:
-
JAILER_ENTITYGRAPH the graph
-
JAILER_ENTITY entity in the graph
-
JAILER_DEPENDENCY dependencies between
entities
For each entity in the graph the primary-key and the
type (as table name) is stored. The birthday of
an entity is the day of the insertion into the
graph.
The graph will be
constructed day after day (step-by-step) starting at day 1:
The progression set of a day is the set of
all tables from which entities are inserted at that day.
The progession set of day 1 is the subject set. The
process stops if the progression set of a day is
empty.
Algorithm
1. insert subject into
graph
2.
progression-set := { subject
}
3. while progression-set !=
{}
1. progression-of-today := {}
2.
for all (restricted) associations A between tables
T1 and
T2, ifT1 or T2 in
progression-set:
1. if T2
(T1) depends on
T1
(T2):
add dependencies from T2(T 1)-entities born yesterday
to the entities they are associated with according to
A
2. insert all entities of T1 (T2), which are associated
according to A
with an entity of T2 (T1) born yesterday
3. if at least one entity of T1 (T2) is inserted then progression-of-today := progression-of-today
+ { T1 (T2) }
3. progression-set :=
progression-of-today
Example
Subject = {
A1,
A2
}
|
day |
progression set |
entities |
dependencies |
| 1 |
A |
A1, A2 |
|
| 2 |
B, C |
+ B1, B2, C3, C4 |
A2->C3, A2->C4 |
| 3 |
B, C |
+ C1, C2, B3, B5 |
+ B1->C1, B1->C2 |
| 4 |
B |
+ B6 |
no change |
| 5 |
|
no change |
no change |
Line 1, insert subject
INSERT INTO JAILER_ENTITY(PK, birthday, type)
SELECT
<subject>.PK, 1, '<subject>'
FROM
<subject>
WHERE (<condition> AND 103
NOT EXISTS (SELECT * FROM JAILER_ENTITY WHERE
<subject>.PK=Entity.PK)
[fetch first <limit> rows only]
Line 3.2.1, adding dependencies
INSERT INTO
JAILER_DEPENDENCY(from_PK, to_PK)
SELECT
<T2>.PK, <T1>.PK
FROM JAILER_ENTITY
E1, JAILER_ENTITY E2,
<T2> JOIN <T1> ON
<join-condition>
WHERE
E1.type='<T1>' AND
E2.type='<T2>'
AND E1.PK=<T1>.PK
AND E2.PK=<T2>.PK
Line 3.2.2, adding referenced entities
INSERT INTO
JAILER_ENTITY(PK, birthday, type)
SELECT
DISTINCT <T2>.PK, <today>,
'<T2>'
FROM
<T1> JOIN <T2> ON
<join-condition>,
Entity
WHERE
<T1>.PK=JAILER_ENTITY.PK AND JAILER_ENTITY.birthday =
<yesterday>
AND NOT EXISTS
(SELECT * FROM JAILER_ENTITY WHERE
<T2>.PK=JAILER_ENTITY.PK)
|
