For no obvious reason, isolationtester has always insisted that
session and step names be written with double quotes. This is
fairly tedious and does little for test readability, especially
since the names that people actually choose almost always look
like normal identifiers. Hence, let's tweak the lexer to allow
SQL-like identifiers not only double-quoted strings.
(They're SQL-like, not exactly SQL, because I didn't add any
case-folding logic. Also there's no provision for U&"..." names,
not that anyone's likely to care.)
There is one incompatibility introduced by this change: if you write
"foo""bar" with no space, that used to be taken as two identifiers,
but now it's just one identifier with an embedded quote mark.
I converted all the src/test/isolation/ specfiles to remove
unnecessary double quotes, but stopped there because my
eyes were glazing over already.
Like 741d7f104, back-patch to all supported branches, so that this
isn't a stumbling block for back-patching isolation test changes.
Discussion: https://postgr.es/m/759113.1623861959@sss.pgh.pa.us
While prior to this patch the user-visible effect on the database
of any set of successfully committed serializable transactions was
always consistent with some one-at-a-time order of execution of
those transactions, the presence of declarative constraints could
allow errors to occur which were not possible in any such ordering,
and developers had no good workarounds to prevent user-facing
errors where they were not necessary or desired. This patch adds
a check for serialization failure ahead of duplicate key checking
so that if a developer explicitly (redundantly) checks for the
pre-existing value they will get the desired serialization failure
where the problem is caused by a concurrent serializable
transaction; otherwise they will get a duplicate key error.
While it would be better if the reads performed by the constraints
could count as part of the work of the transaction for
serialization failure checking, and we will hopefully get there
some day, this patch allows a clean and reliable way for developers
to work around the issue. In many cases existing code will already
be doing the right thing for this to "just work".
Author: Thomas Munro, with minor editing of docs by me
Reviewed-by: Marko Tiikkaja, Kevin Grittner
Tom Lane
Kevin Grittner