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Improve JsonLexContext's freeability

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Previously, the JSON code didn't have to worry too much about freeing
JsonLexContext, because it was never too long-lived.  With new features
being added for SQL/JSON this is no longer the case.  Add a routine
that knows how to free this struct and apply that to a few places, to
prevent this from becoming problematic.

At the same time, we change the API of makeJsonLexContextCstringLen to
make it receive a pointer to JsonLexContext for callers that want it to
be stack-allocated; it can also be passed as NULL to get the original
behavior of a palloc'ed one.

This also causes an ABI break due to the addition of flags to
JsonLexContext, so we can't easily backpatch it.  AFAICS that's not much
of a problem; apparently some leaks might exist in JSON usage of
text-search, for example via json_to_tsvector, but I haven't seen any
complaints about that.

Per Coverity complaint about datum_to_jsonb_internal().

Discussion: https://postgr.es/m/20230808174110.oq3iymllsv6amkih@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2023-10-05 10:59:08 +02:00
parent a8a968a821
commit 1c99cde2f3
7 changed files with 153 additions and 86 deletions
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39
src/backend/utils/adt/json.c
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@@ -106,11 +106,11 @@ json_in(PG_FUNCTION_ARGS)
{
char *json = PG_GETARG_CSTRING(0);
text *result = cstring_to_text(json);
JsonLexContext *lex;
JsonLexContext lex;
/* validate it */
lex = makeJsonLexContext(result, false);
if (!pg_parse_json_or_errsave(lex, &nullSemAction, fcinfo->context))
makeJsonLexContext(&lex, result, false);
if (!pg_parse_json_or_errsave(&lex, &nullSemAction, fcinfo->context))
PG_RETURN_NULL();
/* Internal representation is the same as text */
@@ -152,13 +152,14 @@ json_recv(PG_FUNCTION_ARGS)
StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
char *str;
int nbytes;
JsonLexContext *lex;
JsonLexContext lex;
str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);
/* Validate it. */
lex = makeJsonLexContextCstringLen(str, nbytes, GetDatabaseEncoding(), false);
pg_parse_json_or_ereport(lex, &nullSemAction);
makeJsonLexContextCstringLen(&lex, str, nbytes, GetDatabaseEncoding(),
false);
pg_parse_json_or_ereport(&lex, &nullSemAction);
PG_RETURN_TEXT_P(cstring_to_text_with_len(str, nbytes));
}
@@ -1625,14 +1626,16 @@ json_unique_object_field_start(void *_state, char *field, bool isnull)
bool
json_validate(text *json, bool check_unique_keys, bool throw_error)
{
JsonLexContext *lex = makeJsonLexContext(json, check_unique_keys);
JsonLexContext lex;
JsonSemAction uniqueSemAction = {0};
JsonUniqueParsingState state;
JsonParseErrorType result;
makeJsonLexContext(&lex, json, check_unique_keys);
if (check_unique_keys)
{
state.lex = lex;
state.lex = &lex;
state.stack = NULL;
state.id_counter = 0;
state.unique = true;
@@ -1644,12 +1647,12 @@ json_validate(text *json, bool check_unique_keys, bool throw_error)
uniqueSemAction.object_end = json_unique_object_end;
}
result = pg_parse_json(lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
result = pg_parse_json(&lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
if (result != JSON_SUCCESS)
{
if (throw_error)
json_errsave_error(result, lex, NULL);
json_errsave_error(result, &lex, NULL);
return false; /* invalid json */
}
@@ -1664,6 +1667,9 @@ json_validate(text *json, bool check_unique_keys, bool throw_error)
return false; /* not unique keys */
}
if (check_unique_keys)
freeJsonLexContext(&lex);
return true; /* ok */
}
@@ -1683,18 +1689,17 @@ Datum
json_typeof(PG_FUNCTION_ARGS)
{
text *json = PG_GETARG_TEXT_PP(0);
JsonLexContext *lex = makeJsonLexContext(json, false);
JsonLexContext lex;
char *type;
JsonTokenType tok;
JsonParseErrorType result;
/* Lex exactly one token from the input and check its type. */
result = json_lex(lex);
makeJsonLexContext(&lex, json, false);
result = json_lex(&lex);
if (result != JSON_SUCCESS)
json_errsave_error(result, lex, NULL);
tok = lex->token_type;
json_errsave_error(result, &lex, NULL);
switch (tok)
switch (lex.token_type)
{
case JSON_TOKEN_OBJECT_START:
type = "object";
@@ -1716,7 +1721,7 @@ json_typeof(PG_FUNCTION_ARGS)
type = "null";
break;
default:
elog(ERROR, "unexpected json token: %d", tok);
elog(ERROR, "unexpected json token: %d", lex.token_type);
}
PG_RETURN_TEXT_P(cstring_to_text(type));