Design Change to execute refresh_immv() with False

[jatinp97]

Issue #, if available:
#131

Description of changes:
Set the Dependency type to DEPENDENCY_INTERNAL from DEPENDENCY_AUTO.

By submitting this pull request, I confirm that my contribution is made under the terms of the PostgreSQL license.

Example:

postgres=# create table mytab (i INT);
postgres=# select pgivm.create_immv('myview', 'select * from mytab');
NOTICE:  could not create an index on immv "myview" automatically
DETAIL:  This target list does not have all the primary key columns, or this view does not contain GROUP BY or DISTINCT clause.
HINT:  Create an index on the immv for efficient incremental maintenance.

postgres=# select 'myview'::regclass::oid;
  oid  
-------
 16403
(1 row)

postgres=# select * from pg_trigger where tgrelid = 16403;
oid  | tgrelid | tgparentid |            tgname             | tgfoid | tgtype | tgenabled | tgisinternal | tgconstrrelid | tgconstrindid | tgconstraint | tgdeferrable | tginitdeferred | tgnargs | tgattr | tgargs | tgqual | tgoldtable | tgnewtable 
-------+---------+------------+-------------------------------+--------+--------+-----------+--------------+---------------+---------------+--------------+------------
--+----------------+---------+--------+--------+--------+------------+------------
16417 |   16403 |          0 | IVM_prevent_immv_change_16417 |  16399 |      6 | O         | t            |             0 |             0 |            0 | f          
  | f              |       0 |        | \x      |        |            | 

postgres=# drop trigger "IVM_prevent_immv_change_16417" on myview;
ERROR:  cannot drop trigger IVM_prevent_immv_change_16417 on table myview because table myview requires it
HINT:  You can drop table myview instead.

postgres=# drop trigger "IVM_trigger_ins_before_16406" on mytab;
ERROR:  cannot drop trigger IVM_trigger_ins_before_16406 on table mytab because table myview requires it
HINT:  You can drop table myview instead.
postgres=# drop table mytab;
ERROR:  cannot drop table mytab because other objects depend on it
DETAIL:  table myview depends on table mytab
HINT:  Use DROP ... CASCADE to drop the dependent objects too.

[yugo-n]

Thank you for your pull request!

Although #131 should be fixed, but currently it is intended that we use DEPENDENCY AUTO for an implement reason. Specifically, when refresh_immv() is executed with specified false as the second argument, all triggers are dropped from tables to disable incremental view maintenance. So, your proposal to use DEPENDENCY_INTERNAL disables refresh_immv() to be run with false. To fix #131, first we have to change the design.

[yugo-n]

See the comments in the post
#132 (comment)

[yugo-n]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

AFYI, the license of pg_ivm is PostgreSQL License, not Apache 2.0.
https://github.com/sraoss/pg_ivm/blob/main/LICENSE

[jatinp97]

To circumvent the problem of use of DEPENDENCY_INTERNAL disable refresh_immv() to be run with false, I have used deleteDependencyRecordsFor which is used when redefining an existing object by deleting all records with given depender(classId/objectId). See the changes here

[MasahikoSawada]

While calling deleteDependencyRecordsFor() before dropping the trigger seems workable I have a question about the trigger management design of pg_ivm: can we use enable/disable triggers instead of dropping/recreating them?