postgresql/src/backend/catalog
Bruce Momjian 15cb32d93e This is the final state of the rule system for 6.4 after the
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
1998-08-24 01:38:11 +00:00
..
aclchk.c heap_fetch requires buffer pointer, must be released; heap_getnext 1998-08-19 02:04:17 +00:00
catalog.c heap_fetch requires buffer pointer, must be released; heap_getnext 1998-08-19 02:04:17 +00:00
genbki.sh Add hpux patch for cpp. 1998-04-21 16:18:30 +00:00
heap.c This is the final state of the rule system for 6.4 after the 1998-08-24 01:38:11 +00:00
index.c Fix display in initdb. 1998-08-21 23:22:36 +00:00
indexing.c fix for index problem. 1998-08-20 22:07:46 +00:00
Makefile From: t-ishii@sra.co.jp 1998-07-26 04:31:41 +00:00
pg_aggregate.c heap_fetch requires buffer pointer, must be released; heap_getnext 1998-08-19 02:04:17 +00:00
pg_operator.c heap_fetch requires buffer pointer, must be released; heap_getnext 1998-08-19 02:04:17 +00:00
pg_proc.c This is the final state of the rule system for 6.4 after the 1998-08-24 01:38:11 +00:00
pg_type.c fix for index problem. 1998-08-20 22:07:46 +00:00
README Postgres95 1.01 Distribution - Virgin Sources 1996-07-09 06:22:35 +00:00

$Header: /cvsroot/pgsql/src/backend/catalog/README,v 1.1.1.1 1996/07/09 06:21:15 scrappy Exp $

This directory contains .c files that manipulate the system catalogs
as well as .h files that define the structure of the system catalogs.

When the compile-time scripts (such as Gen_fmgrtab.sh and genbki.sh)
execute, they grep the DATA statements out of the .h files and munge
these in order to generate the .bki files.  The .bki files are then
used as input to initdb (which is just a wrapper around postgres
running single-user in bootstrapping mode) in order to generate the
initial (template) system catalog relation files.

-----------------------------------------------------------------

People who are going to hose around with the .h files should be aware
of the following facts:

- It is very important that the DATA statements be properly formatted
(e.g., no broken lines, proper use of white-space and _null_).  The
scripts are line-oriented and break easily.  In addition, the only
documentation on the proper format for them is the code in the
bootstrap/ directory.  Just be careful when adding new DATA
statements.

- Some catalogs require that OIDs be preallocated to tuples because
certain catalogs contain circular references.  For example, pg_type
contains pointers into pg_proc (pg_type.typinput), and pg_proc
contains back-pointers into pg_type (pg_proc.proargtypes).  In these
cases, the references may be explicitly set by use of the "OID ="
clause of the .bki insert statement.  If no such pointers are required
to a given tuple, then the OID may be set to the wildcard value 0
(i.e., the system generates a random OID in the usual way).

If you need to find a valid OID for a set of tuples that refer to each
other, use the unused_oids script.  It generates inclusive ranges of
*unused* OIDs (i.e., the line "45-900" means OIDs 45 through 900 have
not been allocated yet).  However, you should not rely 100% on this
script, since it only looks at the .h files in the catalog/ directory.
Do a pg_grepsrc (recursive grep) of the source tree to insure that
there aren't any hidden crocks (i.e., explicit use of a numeric OID)
anywhere in the code.

-----------------------------------------------------------------

When munging the .c files, you should be aware of certain conventions:

- The system catalog cache code (and most catalog-munging code in
general) assumes that the fixed-length portion of all system catalog
tuples are in fact present.  That is, only the variable-length
portions of a catalog tuple are assumed to be permitted to be
non-NULL.  For example, if you set pg_type.typdelim to be NULL, a
piece of code will likely perform "typetup->typdelim" (or, worse,
"typetyp->typelem", which follows typdelim).  This will result in
random errors or even segmentation violations.  Hence, do NOT insert
catalog tuples that contain NULL attributes except in their
variable-length portions!

- Modification of the catalogs must be performed with the proper
updating of catalog indexes!  That is, several catalogs have indexes
on them; when you munge them using the executor, the executor will
take care of doing the index updates, but if you make direct access
method calls to insert new or modified tuples into a heap, you must
also make the calls to insert the tuple into ALL of its indexes!  If
not, the new tuple will generally be "invisible" to the system because
most of the accesses to the catalogs in question will be through the
associated indexes.