On 23.02.2011 17:16, Andrew Dunstan wrote:
On 02/23/2011 10:09 AM, Peter Geoghegan wrote:
On 23 February 2011 04:36, Greg Stark<gsst...@mit.edu> wrote:
This is only true for server encodings. In a client library I think
you lose on this and do have to deal with it. I'm not sure what client
encodings we do support that aren't ascii-supersets though, it's
possible none of them generate quote characters this way.
I'm pretty sure all of the client encodings Tatsuo mentions are ASCII
supersets. The absence of by far the most popular non-ASCII superset
encoding, UTF-16, as a client encoding indicated that to me. It isn't
byte oriented, and Postgres is.
They are not. It's precisely because they are not that they are not
allowed as server encodings.
To be precise, they are all ASCII supersets in the sense that a valid
7-bit ASCII string is valid and means the same thing in all of the
client-only encodings as well. The difference between supported
server-encodings and those that are only supported as client_encoding is
whether *all* bytes in a multi-byte character have the high bit set. All
server-encodings have that property, and we rely on it in the backend.
In the supported client-only encodings, the *first* byte of a multi-byte
character is guaranteed to have the high bit set, but the subsequent
bytes are not.
Even that more loose property isn't true for UTF-16, which is why we
don't support it even as a client-only encoding.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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