Fixes a bug in the rule system that caused a crashing
backend when a join-view with calculated column is used
in subselect.
Modifies EXPLAIN to explain rewritten queries instead of
the plain SeqScan on a view. Rules can produce very deep
MORE
Jan.
for against a just updated CVS tree. It contains
Partial new rewrite system that handles subselects, view
aggregate columns, insert into select from view, updates
with set col = view-value and select rules restriction to
view definition.
Updates for rule/view backparsing utility functions to
handle subselects correct.
New system views pg_tables and pg_indexes (where you can
see the complete index definition in the latter one).
Enabling array references on query parameters.
Bugfix for functional index.
Little changes to system views pg_rules and pg_views.
The rule system isn't a release-stopper any longer.
But another stopper is that I don't know if the latest
changes to PL/pgSQL (not already in CVS) made it compile on
AIX. Still wait for some response from Dave.
Jan
patch is applied:
Rewrite rules on relation level work fine now.
Event qualifications on insert/update/delete rules work
fine now.
I added the new keyword OLD to reference the CURRENT
tuple. CURRENT will be removed in 6.5.
Update rules can reference NEW and OLD in the rule
qualification and the actions.
Insert/update/delete rules on views can be established to
let them behave like real tables.
For insert/update/delete rules multiple actions are
supported now. The actions can also be surrounded by
parantheses to make psql happy. Multiple actions are
required if update to a view requires updates to multiple
tables.
Regular users are permitted to create/drop rules on
tables they have RULE permissions for
(DefineQueryRewrite() is now able to get around the
access restrictions on pg_rewrite). This enables view
creation for regular users too. This required an extra
boolean parameter to pg_parse_and_plan() that tells to
set skipAcl on all rangetable entries of the resulting
queries. There is a new function
pg_exec_query_acl_override() that could be used by
backend utilities to use this facility.
All rule actions (not only views) inherit the permissions
of the event relations owner. Sample: User A creates
tables T1 and T2, creates rules that log
INSERT/UPDATE/DELETE on T1 in T2 (like in the regression
tests for rules I created) and grants ALL but RULE on T1
to user B. User B can now fully access T1 and the
logging happens in T2. But user B cannot access T2 at
all, only the rule actions can. And due to missing RULE
permissions on T1, user B cannot disable logging.
Rules on the attribute level are disabled (they don't
work properly and since regular users are now permitted
to create rules I decided to disable them).
Rules on select must have exactly one action that is a
select (so select rules must be a view definition).
UPDATE NEW/OLD rules are disabled (still broken, but
triggers can do it).
There are two new system views (pg_rule and pg_view) that
show the definition of the rules or views so the db admin
can see what the users do. They use two new functions
pg_get_ruledef() and pg_get_viewdef() that are builtins.
The functions pg_get_ruledef() and pg_get_viewdef() could
be used to implement rule and view support in pg_dump.
PostgreSQL is now the only database system I know, that
has rewrite rules on the query level. All others (where I
found a rule statement at all) use stored database
procedures or the like (triggers as we call them) for
active rules (as some call them).
Future of the rule system:
The now disabled parts of the rule system (attribute
level, multiple actions on select and update new stuff)
require a complete new rewrite handler from scratch. The
old one is too badly wired up.
After 6.4 I'll start to work on a new rewrite handler,
that fully supports the attribute level rules, multiple
actions on select and update new. This will be available
for 6.5 so we get full rewrite rule capabilities.
Jan
no longer returns buffer pointer, can be gotten from scan;
descriptor; bootstrap can create multi-key indexes;
pg_procname index now is multi-key index; oidint2, oidint4, oidname
are gone (must be removed from regression tests); use System Cache
rather than sequential scan in many places; heap_modifytuple no
longer takes buffer parameter; remove unused buffer parameter in
a few other functions; oid8 is not index-able; remove some use of
single-character variable names; cleanup Buffer variables usage
and scan descriptor looping; cleaned up allocation and freeing of
tuples; 18k lines of diff;
now. Here some tested features, (examples included in the patch):
1.1) Subselects in the having clause 1.2) Double nested subselects
1.3) Subselects used in the where clause and in the having clause
simultaneously 1.4) Union Selects using having 1.5) Indexes
on the base relations are used correctly 1.6) Unallowed Queries
are prevented (e.g. qualifications in the
having clause that belong to the where clause) 1.7) Insert
into as select
2) Queries using the having clause on view relations also work
but there are some restrictions:
2.1) Create View as Select ... Having ...; using base tables in
the select 2.1.1) The Query rewrite system:
2.1.2) Why are only simple queries allowed against a view from 2.1)
? 2.2) Select ... from testview1, testview2, ... having...; 3) Bug
in ExecMergeJoin ??
Regards Stefan
sequential scans! (I think it will also work with hash, index, etc
but I did not check it out! I made some High level changes which
should work for all access methods, but maybe I'm wrong. Please
let me know.)
Now it is possible to make queries like:
select s.sname, max(p.pid), min(p.pid) from part p, supplier s
where s.sid=p.sid group by s.sname having max(pid)=6 and min(pid)=1
or avg(pid)=4;
Having does not work yet for queries that contain a subselect
statement in the Having clause, I'll try to fix this in the next
days.
If there are some bugs, please let me know, I'll start to read the
mailinglists now!
Now here is the patch against the original 6.3 version (no snapshot!!):
Stefan
seems that my last post didn't make it through. That's good
since the diff itself didn't covered the renaming of
pg_user.h to pg_shadow.h and it's new content.
Here it's again. The complete regression test passwd with
only some float diffs. createuser and destroyuser work.
pg_shadow cannot be read by ordinary user.
below is the patch to have views to override the permission
checks for the accessed tables. Now we can do the following:
CREATE VIEW db_user AS SELECT
usename,
usesysid,
usecreatedb,
usetrace,
usecatupd,
'**********'::text as passwd,
valuntil
FROM pg_user;
REVOKE ALL ON pg_user FROM public;
REVOKE ALL ON db_user FROM public;
GRANT SELECT ON db_user TO public;
Thomas G. Lockhart