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Fix jsonb Unicode escape processing, and in consequence disallow \u0000.

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We've been trying to support \u0000 in JSON values since commit
78ed8e03c6, and have introduced increasingly worse hacks to try to
make it work, such as commit 0ad1a81632.  However, it fundamentally
can't work in the way envisioned, because the stored representation looks
the same as for \\u0000 which is not the same thing at all.  It's also
entirely bogus to output \u0000 when de-escaped output is called for.

The right way to do this would be to store an actual 0x00 byte, and then
throw error only if asked to produce de-escaped textual output.  However,
getting to that point seems likely to take considerable work and may well
never be practical in the 9.4.x series.

To preserve our options for better behavior while getting rid of the nasty
side-effects of 0ad1a81632, revert that commit in toto and instead
throw error if \u0000 is used in a context where it needs to be de-escaped.
(These are the same contexts where non-ASCII Unicode escapes throw error
if the database encoding isn't UTF8, so this behavior is by no means
without precedent.)

In passing, make both the \u0000 case and the non-ASCII Unicode case report
ERRCODE_UNTRANSLATABLE_CHARACTER / "unsupported Unicode escape sequence"
rather than claiming there's something wrong with the input syntax.

Back-patch to 9.4, where we have to do something because 0ad1a81632
broke things for many cases having nothing to do with \u0000.  9.3 also has
bogus behavior, but only for that specific escape value, so given the lack
of field complaints it seems better to leave 9.3 alone.
This commit is contained in:
Tom Lane
2015-01-30 14:44:46 -05:00
parent e40d43f88e
commit 451d280815
9 changed files with 250 additions and 160 deletions
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18
src/test/regress/sql/json.sql
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@ -111,14 +111,6 @@ SET LOCAL TIME ZONE -8;
select to_json(timestamptz '2014-05-28 12:22:35.614298-04');
COMMIT;
-- unicode escape - backslash is not escaped
select to_json(text '\uabcd');
-- any other backslash is escaped
select to_json(text '\abcd');
--json_agg
SELECT json_agg(q)
@ -401,9 +393,17 @@ select json '{ "a": "\ude04X" }' -> 'a'; -- orphan low surrogate
--handling of simple unicode escapes
select json '{ "a": "the Copyright \u00a9 sign" }' as correct_in_utf8;
select json '{ "a": "dollar \u0024 character" }' as correct_everywhere;
select json '{ "a": "dollar \\u0024 character" }' as not_an_escape;
select json '{ "a": "null \u0000 escape" }' as not_unescaped;
select json '{ "a": "null \\u0000 escape" }' as not_an_escape;
select json '{ "a": "the Copyright \u00a9 sign" }' ->> 'a' as correct_in_utf8;
select json '{ "a": "dollar \u0024 character" }' ->> 'a' as correct_everywhere;
select json '{ "a": "null \u0000 escape" }' ->> 'a' as not_unescaped;
select json '{ "a": "dollar \\u0024 character" }' ->> 'a' as not_an_escape;
select json '{ "a": "null \u0000 escape" }' ->> 'a' as fails;
select json '{ "a": "null \\u0000 escape" }' ->> 'a' as not_an_escape;
--json_typeof() function
select value, json_typeof(value)