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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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107
src/backend/utils/adt/jsonfuncs.c
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@ -526,7 +526,7 @@ pg_parse_json_or_errsave(JsonLexContext *lex, JsonSemAction *sem,
* directly.
*/
JsonLexContext *
makeJsonLexContext(text *json, bool need_escapes)
makeJsonLexContext(JsonLexContext *lex, text *json, bool need_escapes)
{
/*
* Most callers pass a detoasted datum, but it's not clear that they all
@ -534,7 +534,8 @@ makeJsonLexContext(text *json, bool need_escapes)
*/
json = pg_detoast_datum_packed(json);
return makeJsonLexContextCstringLen(VARDATA_ANY(json),
return makeJsonLexContextCstringLen(lex,
VARDATA_ANY(json),
VARSIZE_ANY_EXHDR(json),
GetDatabaseEncoding(),
need_escapes);
@ -725,7 +726,7 @@ json_object_keys(PG_FUNCTION_ARGS)
if (SRF_IS_FIRSTCALL())
{
text *json = PG_GETARG_TEXT_PP(0);
JsonLexContext *lex = makeJsonLexContext(json, true);
JsonLexContext lex;
JsonSemAction *sem;
MemoryContext oldcontext;
@ -735,7 +736,7 @@ json_object_keys(PG_FUNCTION_ARGS)
state = palloc(sizeof(OkeysState));
sem = palloc0(sizeof(JsonSemAction));
state->lex = lex;
state->lex = makeJsonLexContext(&lex, json, true);
state->result_size = 256;
state->result_count = 0;
state->sent_count = 0;
@ -747,12 +748,10 @@ json_object_keys(PG_FUNCTION_ARGS)
sem->object_field_start = okeys_object_field_start;
/* remainder are all NULL, courtesy of palloc0 above */
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
/* keys are now in state->result */
pfree(lex->strval->data);
pfree(lex->strval);
pfree(lex);
freeJsonLexContext(&lex);
pfree(sem);
MemoryContextSwitchTo(oldcontext);
@ -1096,13 +1095,13 @@ get_worker(text *json,
int npath,
bool normalize_results)
{
JsonLexContext *lex = makeJsonLexContext(json, true);
JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
GetState *state = palloc0(sizeof(GetState));
Assert(npath >= 0);
state->lex = lex;
state->lex = makeJsonLexContext(NULL, json, true);
/* is it "_as_text" variant? */
state->normalize_results = normalize_results;
state->npath = npath;
@ -1140,7 +1139,8 @@ get_worker(text *json,
sem->array_element_end = get_array_element_end;
}
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(state->lex, sem);
freeJsonLexContext(state->lex);
return state->tresult;
}
@ -1842,25 +1842,23 @@ json_array_length(PG_FUNCTION_ARGS)
{
text *json = PG_GETARG_TEXT_PP(0);
AlenState *state;
JsonLexContext *lex;
JsonLexContext lex;
JsonSemAction *sem;
lex = makeJsonLexContext(json, false);
state = palloc0(sizeof(AlenState));
sem = palloc0(sizeof(JsonSemAction));
state->lex = makeJsonLexContext(&lex, json, false);
/* palloc0 does this for us */
#if 0
state->count = 0;
#endif
state->lex = lex;
sem = palloc0(sizeof(JsonSemAction));
sem->semstate = (void *) state;
sem->object_start = alen_object_start;
sem->scalar = alen_scalar;
sem->array_element_start = alen_array_element_start;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(state->lex, sem);
PG_RETURN_INT32(state->count);
}
@ -2049,12 +2047,11 @@ static Datum
each_worker(FunctionCallInfo fcinfo, bool as_text)
{
text *json = PG_GETARG_TEXT_PP(0);
JsonLexContext *lex;
JsonLexContext lex;
JsonSemAction *sem;
ReturnSetInfo *rsi;
EachState *state;
lex = makeJsonLexContext(json, true);
state = palloc0(sizeof(EachState));
sem = palloc0(sizeof(JsonSemAction));
@ -2072,14 +2069,15 @@ each_worker(FunctionCallInfo fcinfo, bool as_text)
state->normalize_results = as_text;
state->next_scalar = false;
state->lex = lex;
state->lex = makeJsonLexContext(&lex, json, true);
state->tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"json_each temporary cxt",
ALLOCSET_DEFAULT_SIZES);
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
MemoryContextDelete(state->tmp_cxt);
freeJsonLexContext(&lex);
PG_RETURN_NULL();
}
@ -2299,13 +2297,14 @@ static Datum
elements_worker(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
{
text *json = PG_GETARG_TEXT_PP(0);
/* elements only needs escaped strings when as_text */
JsonLexContext *lex = makeJsonLexContext(json, as_text);
JsonLexContext lex;
JsonSemAction *sem;
ReturnSetInfo *rsi;
ElementsState *state;
/* elements only needs escaped strings when as_text */
makeJsonLexContext(&lex, json, as_text);
state = palloc0(sizeof(ElementsState));
sem = palloc0(sizeof(JsonSemAction));
@ -2323,14 +2322,15 @@ elements_worker(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
state->function_name = funcname;
state->normalize_results = as_text;
state->next_scalar = false;
state->lex = lex;
state->lex = &lex;
state->tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"json_array_elements temporary cxt",
ALLOCSET_DEFAULT_SIZES);
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
MemoryContextDelete(state->tmp_cxt);
freeJsonLexContext(&lex);
PG_RETURN_NULL();
}
@ -2704,7 +2704,8 @@ populate_array_json(PopulateArrayContext *ctx, char *json, int len)
PopulateArrayState state;
JsonSemAction sem;
state.lex = makeJsonLexContextCstringLen(json, len, GetDatabaseEncoding(), true);
state.lex = makeJsonLexContextCstringLen(NULL, json, len,
GetDatabaseEncoding(), true);
state.ctx = ctx;
memset(&sem, 0, sizeof(sem));
@ -2720,7 +2721,7 @@ populate_array_json(PopulateArrayContext *ctx, char *json, int len)
/* number of dimensions should be already known */
Assert(ctx->ndims > 0 && ctx->dims);
pfree(state.lex);
freeJsonLexContext(state.lex);
}
/*
@ -3547,7 +3548,6 @@ get_json_object_as_hash(char *json, int len, const char *funcname)
HASHCTL ctl;
HTAB *tab;
JHashState *state;
JsonLexContext *lex = makeJsonLexContextCstringLen(json, len, GetDatabaseEncoding(), true);
JsonSemAction *sem;
ctl.keysize = NAMEDATALEN;
@ -3563,7 +3563,8 @@ get_json_object_as_hash(char *json, int len, const char *funcname)
state->function_name = funcname;
state->hash = tab;
state->lex = lex;
state->lex = makeJsonLexContextCstringLen(NULL, json, len,
GetDatabaseEncoding(), true);
sem->semstate = (void *) state;
sem->array_start = hash_array_start;
@ -3571,7 +3572,9 @@ get_json_object_as_hash(char *json, int len, const char *funcname)
sem->object_field_start = hash_object_field_start;
sem->object_field_end = hash_object_field_end;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(state->lex, sem);
freeJsonLexContext(state->lex);
return tab;
}
@ -3863,12 +3866,12 @@ populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
if (is_json)
{
text *json = PG_GETARG_TEXT_PP(json_arg_num);
JsonLexContext *lex;
JsonLexContext lex;
JsonSemAction *sem;
sem = palloc0(sizeof(JsonSemAction));
lex = makeJsonLexContext(json, true);
makeJsonLexContext(&lex, json, true);
sem->semstate = (void *) state;
sem->array_start = populate_recordset_array_start;
@ -3879,9 +3882,12 @@ populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
sem->object_start = populate_recordset_object_start;
sem->object_end = populate_recordset_object_end;
state->lex = lex;
state->lex = &lex;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
freeJsonLexContext(&lex);
state->lex = NULL;
}
else
{
@ -4217,16 +4223,15 @@ json_strip_nulls(PG_FUNCTION_ARGS)
{
text *json = PG_GETARG_TEXT_PP(0);
StripnullState *state;
JsonLexContext *lex;
JsonLexContext lex;
JsonSemAction *sem;
lex = makeJsonLexContext(json, true);
state = palloc0(sizeof(StripnullState));
sem = palloc0(sizeof(JsonSemAction));
state->lex = makeJsonLexContext(&lex, json, true);
state->strval = makeStringInfo();
state->skip_next_null = false;
state->lex = lex;
sem->semstate = (void *) state;
sem->object_start = sn_object_start;
@ -4237,7 +4242,7 @@ json_strip_nulls(PG_FUNCTION_ARGS)
sem->array_element_start = sn_array_element_start;
sem->object_field_start = sn_object_field_start;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
PG_RETURN_TEXT_P(cstring_to_text_with_len(state->strval->data,
state->strval->len));
@ -5433,11 +5438,11 @@ void
iterate_json_values(text *json, uint32 flags, void *action_state,
JsonIterateStringValuesAction action)
{
JsonLexContext *lex = makeJsonLexContext(json, true);
JsonLexContext lex;
JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
IterateJsonStringValuesState *state = palloc0(sizeof(IterateJsonStringValuesState));
state->lex = lex;
state->lex = makeJsonLexContext(&lex, json, true);
state->action = action;
state->action_state = action_state;
state->flags = flags;
@ -5446,7 +5451,8 @@ iterate_json_values(text *json, uint32 flags, void *action_state,
sem->scalar = iterate_values_scalar;
sem->object_field_start = iterate_values_object_field_start;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
freeJsonLexContext(&lex);
}
/*
@ -5553,11 +5559,11 @@ text *
transform_json_string_values(text *json, void *action_state,
JsonTransformStringValuesAction transform_action)
{
JsonLexContext *lex = makeJsonLexContext(json, true);
JsonLexContext lex;
JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
TransformJsonStringValuesState *state = palloc0(sizeof(TransformJsonStringValuesState));
state->lex = lex;
state->lex = makeJsonLexContext(&lex, json, true);
state->strval = makeStringInfo();
state->action = transform_action;
state->action_state = action_state;
@ -5571,7 +5577,8 @@ transform_json_string_values(text *json, void *action_state,
sem->array_element_start = transform_string_values_array_element_start;
sem->object_field_start = transform_string_values_object_field_start;
pg_parse_json_or_ereport(lex, sem);
pg_parse_json_or_ereport(&lex, sem);
freeJsonLexContext(&lex);
return cstring_to_text_with_len(state->strval->data, state->strval->len);
}
@ -5670,19 +5677,19 @@ transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype
JsonTokenType
json_get_first_token(text *json, bool throw_error)
{
JsonLexContext *lex;
JsonLexContext lex;
JsonParseErrorType result;
lex = makeJsonLexContext(json, false);
makeJsonLexContext(&lex, json, false);
/* Lex exactly one token from the input and check its type. */
result = json_lex(lex);
result = json_lex(&lex);
if (result == JSON_SUCCESS)
return lex->token_type;
return lex.token_type;
if (throw_error)
json_errsave_error(result, lex, NULL);
json_errsave_error(result, &lex, NULL);
return JSON_TOKEN_INVALID; /* invalid json */
}