| From: | Ken Johanson <pg-user(at)kensystem(dot)com> |
|---|---|
| To: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Possible to run the server with ANSI/ISO string escapeing |
| Date: | 2005-02-28 16:40:55 |
| Message-ID: | 42234997.2070403@kensystem.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
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| Lists: | pgsql-general |
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Martijn van Oosterhout wrote:
<blockquote cite="mid20050228091645(dot)GA27668(at)svana(dot)org" type="cite">
<pre wrap="">On Sun, Feb 27, 2005 at 06:25:18PM -0700, Ken Johanson wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I feel somewhat confident (very actually) that a config option that
disabled the backslash behavior globally(*) would be acceptable, BUT
leave the current backslash behavior turned on by default so that
current users are not impacted at all. Only a conscientious decision by
the db admin to turn it on could cause problems, but _only_ if he/she
didn't warn all his/her users beforehand of the impending change and its
consequences (rtm).
</pre>
</blockquote>
<pre wrap=""><!---->
It's not just a question of warning the users, all interfaces to the
database will instantly break. For example: JDBC, Perl DBI, PHP PEAR
etc. They will continue to send queries with the backslashes embedded.
These interfaces would need to be modified to handle both situations
and detect which situation they're dealing with.
</pre>
</blockquote>
All interfaces will NOT break IF the legacy db behavior stays its
default. This means NONE of the current users would be hurt until they
start experimenting with the new option. Yes, the built in prepared
stmt components of those interfaces will still add the backslash by
default and break queries for legacy drivers, but this is not an issue
for the straight-through query/update exec(s) calls, and prepared stmt
users can hack the Prepared stmts behavior until the same option is
officially supported in the driver also (probably by auto-detecting
what the DB expects its backslashes to look like).<br>
<br>
Like I said, users should be warned beforehand, that they need to get a
hacked or official driver update, if the dbadmin decides to turn on the
'new' mode. Seems prudent to me.<br>
<blockquote cite="mid20050228091645(dot)GA27668(at)svana(dot)org" type="cite">
<pre wrap="">
The thing is all these interfaces handle the quoting transparently for
you, so the code is portable already. What you're complaining about is
that you have your own query marshalling and it is not portable.
</pre>
</blockquote>
As you say, the portability you describe REQUIRES the use of prepared
stmts type queries - but one CANNOT issue a portable query, say,
jdbc:stmt.execQuery() or execute update. Those "lower-level" calls need
to be portable where string escaping is concerned, and they are not.
They arguably break both the JDBC spec and SQL spec since some
additional, nonstandard string preprocessing is REQUIRED for them to
work. And not to repeat what you already know, but Prepared stmts are
not suitable or available for certain query types (performance
sometimes better w/o PS, dynamic query building, batch queries,
etc) and drivers (small foot print ones).<br>
<blockquote cite="mid20050228091645(dot)GA27668(at)svana(dot)org" type="cite">
<pre wrap="">
Incidently, if you disable the backslash quoting, how does one enter
raw binary data including NUL (\0) characters?
</pre>
</blockquote>
I'm not sure if you're talking about API interfaces or shell, or both.
If shell, a piped sql-compliant escape processor would clearly be
needed.<br>
<br>
As for APIs, I suspect the current design of each driver handles nulls
and the like, stems from how the underlying db protocol was originally
built --so they use either run length encoding (chunking),
boundary-delimiting, or are null terminated (whichever PG uses
natively, I don't know). In any case the very lowest level of the db
interface can translate as necessary (doubling the backslashes if
necessary), but queries should be able to issue any byte, including
nulls, with the only requirement that apostrophes are the string-escape
character, for themselves. In other words nulls should need no special
treatment from the query interface layer.<br>
<blockquote cite="mid20050228091645(dot)GA27668(at)svana(dot)org" type="cite">
<pre wrap="">
The only viable solution I can think of is that it is set at
*connection* time (maybe extra parameters), and unchangable for the
rest of the session. This means that unmodified client interfaces won't
see a difference.
</pre>
</blockquote>
Yes, sessions (connections) could work, and also perhaps per-user or
group, wherein the db the escape handing is handled the old or new way
on a per-user basis.<br>
<blockquote cite="mid20050228091645(dot)GA27668(at)svana(dot)org" type="cite">
<pre wrap=""></pre>
<blockquote type="cite">
<pre wrap="">I can say, that I for one would enable the no-backslash config option
out of the box -globally -so that we can start using pg now without any
more upper managerial concerns/excuses about language/interface
compliance..I can also say that (what we already know) the longer we
wait to provide the 'right' option, the *more* legacy apps (and
interfaces) will be built around it and consequently suffer when the
need for change eventually comes (almost wholly caused by interop
concerns). And market gain is being hurt now by this incompatibility
with commercial offerings; that's an unfortunate fact.
</pre>
</blockquote>
<pre wrap=""><!---->
Even if PostgreSQL implements this now, you will have to wait for new
versions of any client libraries before it's usable. See the autocommit
disaster for an example why people are not rushing into this...
</pre>
</blockquote>
I fully agree. I can see waiting at LEAST 1-3 months before the db
itself has changes committed for alpha testing, but that SURE BEATS
procrastination --which means years worth of more apps and interfaces
being built around the 'backslash' (again, not everyone uses prepared
statement - its not required and not suitable for all situations).
Conversely, the very day the server has an alpha build supporting the
no-backslash mode is the very _first_ day that the jdbc/perl driver
developers can start testing against the changes. Until then all
parties are just sitting still.<br>
<br>
Incidentally, I believe PG is now one of the last widely used DBs to
not offer the standard escape behavior; the other popular OS db now has
this option (albeit buggy), at the request of a very large software
company that wanted to adopt their db no less...<br>
<br>
Let me just finish by saying that I'm uncomfortable and sorry to be
making waves like I am, but I feel it's in everyones best interest long
term to start making this change now and teach the users sooner than
later - this topic is has been a real handicap for my own adoption of
the database (peer-wise), and the problem will only fester if nothing
is done. Pain now or pain later.<br>
<br>
ken<br>
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