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Tom Lane 17b7c302b5 Fully enforce uniqueness of constraint names.
It's been true for a long time that we expect names of table and domain
constraints to be unique among the constraints of that table or domain.
However, the enforcement of that has been pretty haphazard, and it missed
some corner cases such as creating a CHECK constraint and then an index
constraint of the same name (as per recent report from André Hänsel).
Also, due to the lack of an actual unique index enforcing this, duplicates
could be created through race conditions.

Moreover, the code that searches pg_constraint has been quite inconsistent
about how to handle duplicate names if one did occur: some places checked
and threw errors if there was more than one match, while others just
processed the first match they came to.

To fix, create a unique index on (conrelid, contypid, conname).  Since
either conrelid or contypid is zero, this will separately enforce
uniqueness of constraint names among constraints of any one table and any
one domain.  (If we ever implement SQL assertions, and put them into this
catalog, more thought might be needed.  But it'd be at least as reasonable
to put them into a new catalog; having overloaded this one catalog with
two kinds of constraints was a mistake already IMO.)  This index can replace
the existing non-unique index on conrelid, though we need to keep the one
on contypid for query performance reasons.

Having done that, we can simplify the logic in various places that either
coped with duplicates or neglected to, as well as potentially improve
lookup performance when searching for a constraint by name.

Also, as per our usual practice, install a preliminary check so that you
get something more friendly than a unique-index violation report in the
case complained of by André.  And teach ChooseIndexName to avoid choosing
autogenerated names that would draw such a failure.

While it's not possible to make such a change in the back branches,
it doesn't seem quite too late to put this into v11, so do so.

Discussion: https://postgr.es/m/0c1001d4428f$0942b430$1bc81c90$@webkr.de
2018-09-04 13:45:35 -04:00
config Remove test for VA_ARGS, implied by C99. 2018-08-24 10:41:45 -07:00
contrib Clean up after TAP tests in oid2name and vacuumlo. 2018-09-04 10:52:01 -04:00
doc Fully enforce uniqueness of constraint names. 2018-09-04 13:45:35 -04:00
src Fully enforce uniqueness of constraint names. 2018-09-04 13:45:35 -04:00
.dir-locals.el Update documentation editor setup instructions 2018-07-13 21:23:41 +02:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
COPYRIGHT Update copyright for 2018 2018-01-02 23:30:12 -05:00
GNUmakefile.in Remove unwanted "garbage cleanup" logic in Makefiles. 2018-08-08 14:32:29 -04:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:22 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
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README

PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.