postgres

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Tom Lane 4c804fbdfb Clean up parsing of synchronous_standby_names GUC variable. Commit `989be0810d` added a flex/bison lexer/parser to interpret synchronous_standby_names. It was done in a pretty crufty way, though, making assorted end-use sites responsible for calling the parser at the right times. That was not only vulnerable to errors of omission, but made it possible that lexer/parser errors occur at very undesirable times, and created memory leakages even if there was no error. Instead, perform the parsing once during check_synchronous_standby_names and let guc.c manage the resulting data. To do that, we have to flatten the parsed representation into a single hunk of malloc'd memory, but that is not very hard. While at it, work a little harder on making useful error reports for parsing problems; the previous code felt that "synchronous_standby_names parser returned 1" was an appropriate user-facing error message. (To be fair, it did also log a syntax error message, but separately from the GUC problem report, which is at best confusing.) It had some outright bugs in the face of invalid input, too. I (tgl) also concluded that we need to restrict unquoted names in synchronous_standby_names to be just SQL identifiers. The previous coding would accept darn near anything, which (1) makes the quoting convention both nearly-unnecessary and formally ambiguous, (2) makes it very hard to understand what is a syntax error and what is a creative interpretation of the input as a standby name, and (3) makes it impossible to further extend the syntax in future without a compatibility break. I presume that we're intending future extensions of the syntax, else this parsing infrastructure is massive overkill, so (3) is an important objection. Since we've taken a compatibility hit for non-identifier names with this change anyway, we might as well lock things down now and insist that users use double quotes for standby names that aren't identifiers. Kyotaro Horiguchi and Tom Lane	10 years ago
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sgml	Clean up parsing of synchronous_standby_names GUC variable.	10 years ago
Makefile	…

Tom Lane 4c804fbdfb Clean up parsing of synchronous_standby_names GUC variable.

Commit 989be0810d added a flex/bison lexer/parser to interpret
synchronous_standby_names.  It was done in a pretty crufty way, though,
making assorted end-use sites responsible for calling the parser at the
right times.  That was not only vulnerable to errors of omission, but made
it possible that lexer/parser errors occur at very undesirable times,
and created memory leakages even if there was no error.

Instead, perform the parsing once during check_synchronous_standby_names
and let guc.c manage the resulting data.  To do that, we have to flatten
the parsed representation into a single hunk of malloc'd memory, but that
is not very hard.

While at it, work a little harder on making useful error reports for
parsing problems; the previous code felt that "synchronous_standby_names
parser returned 1" was an appropriate user-facing error message.  (To
be fair, it did also log a syntax error message, but separately from the
GUC problem report, which is at best confusing.)  It had some outright
bugs in the face of invalid input, too.

I (tgl) also concluded that we need to restrict unquoted names in
synchronous_standby_names to be just SQL identifiers.  The previous coding
would accept darn near anything, which (1) makes the quoting convention
both nearly-unnecessary and formally ambiguous, (2) makes it very hard to
understand what is a syntax error and what is a creative interpretation of
the input as a standby name, and (3) makes it impossible to further extend
the syntax in future without a compatibility break.  I presume that we're
intending future extensions of the syntax, else this parsing infrastructure
is massive overkill, so (3) is an important objection.  Since we've taken
a compatibility hit for non-identifier names with this change anyway, we
might as well lock things down now and insist that users use double quotes
for standby names that aren't identifiers.

Kyotaro Horiguchi and Tom Lane

10 years ago

sgml Clean up parsing of synchronous_standby_names GUC variable. 10 years ago

Makefile

…