On Mon, Feb 05, 2024 at 06:05:04PM -0800, Andres Freund wrote: > I don't really understand why we need to validate anything during COPY TO? > Which is good, because it turns out that we don't actually validate anything, > as pg_server_to_any() returns without doing anything if the encoding matches: > > if (encoding == DatabaseEncoding->encoding || > encoding == PG_SQL_ASCII) > return unconstify(char *, s); /* assume data is valid */ > > This means that the strlen() we do in the call do pg_server_to_any(), which on > its own takes 14.25% of the cycles, computes something that will never be > used.
Indeed, that's wasting cycles for nothing when the client and server encoding match. > Unsurprisingly, only doing transcoding when encodings differ yields a sizable > improvement, about 18% for [2]. > > I haven't yet dug into the code history. One guess is that this should only > have been set this way for COPY FROM. Looking the git history, this looks like an oversight of c61a2f58418e that has added the condition on pg_database_encoding_max_length(), no? Adding Tom and Ishii-san, even if this comes from 2005. -- Michael
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