8000 Improve JsonLexContext's freeability · postgres/postgres@1c99cde · GitHub
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alvherrealvherre
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Improve JsonLexContext's freeability
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
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7 files changed

+153
-86
lines changed
  • bin/pg_verifybackup
  • common
  • include

    • 7 files changed

    +153
    -86
    lines changed

    ‎src/backend/utils/adt/json.c

    Lines changed: 22 additions & 17 deletions
    Original file line numberDiff line numberDiff line change
    @@ -106,11 +106,11 @@ json_in(PG_FUNCTION_ARGS)
    106106
    {
    107107
    char *json = PG_GETARG_CSTRING(0);
    108108
    text *result = cstring_to_text(json);
    109-
    JsonLexContext *lex;
    109+
    JsonLexContext lex;
    110110

    111111
    /* validate it */
    112-
    lex = makeJsonLexContext(result, false);
    113-
    if (!pg_parse_json_or_errsave(lex, &nullSemAction, fcinfo->context))
    112+
    makeJsonLexContext(&lex, result, false);
    113+
    if (!pg_parse_json_or_errsave(&lex, &nullSemAction, fcinfo->context))
    114114
    PG_RETURN_NULL();
    115115

    116116
    /* Internal representation is the same as text */
    @@ -152,13 +152,14 @@ json_recv(PG_FUNCTION_ARGS)
    152152
    StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
    153153
    char *str;
    154154
    int nbytes;
    155-
    JsonLexContext *lex;
    155+
    JsonLexContext lex;
    156156

    157157
    str = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);
    158158

    159159
    /* Validate it. */
    160-
    lex = makeJsonLexContextCstringLen(str, nbytes, GetDatabaseEncoding(), false);
    161-
    pg_parse_json_or_ereport(lex, &nullSemAction);
    160+
    makeJsonLexContextCstringLen(&lex, str, nbytes, GetDatabaseEncoding(),
    161+
    false);
    162+
    pg_parse_json_or_ereport(&lex, &nullSemAction);
    162163

    163164
    PG_RETURN_TEXT_P(cstring_to_text_with_len(str, nbytes));
    164165
    }
    @@ -1625,14 +1626,16 @@ json_unique_object_field_start(void *_state, char *field, bool isnull)
    16251626
    bool
    16261627
    json_validate(text *json, bool check_unique_keys, bool throw_error)
    16271628
    {
    1628-
    JsonLexContext *lex = makeJsonLexContext(json, check_unique_keys);
    1629+
    JsonLexContext lex;
    16291630
    JsonSemAction uniqueSemAction = {0};
    16301631
    JsonUniqueParsingState state;
    16311632
    JsonParseErrorType result;
    16321633

    1634+
    makeJsonLexContext(&lex, json, check_unique_keys);
    1635+
    16331636
    if (check_unique_keys)
    16341637
    {
    1635-
    state.lex = lex;
    1638+
    state.lex = &lex;
    16361639
    state.stack = NULL;
    16371640
    state.id_counter = 0;
    16381641
    state.unique = true;
    @@ -1644,12 +1647,12 @@ json_validate(text *json, bool check_unique_keys, bool throw_error)
    16441647
    uniqueSemAction.object_end = json_unique_object_end;
    16451648
    }
    16461649

    1647-
    result = pg_parse_json(lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
    1650+
    result = pg_parse_json(&lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
    16481651

    16491652
    if (result != JSON_SUCCESS)
    16501653
    {
    16511654
    if (throw_error)
    1652-
    json_errsave_error(result, lex, NULL);
    1655+
    json_errsave_error(result, &lex, NULL);
    16531656

    16541657
    return false; /* invalid json */
    16551658
    }
    @@ -1664,6 +1667,9 @@ json_validate(text *json, bool check_unique_keys, bool throw_error)
    16641667
    return false; /* not unique keys */
    16651668
    }
    16661669

    1670+
    if (check_unique_keys)
    1671+
    freeJsonLexContext(&lex);
    1672+
    16671673
    return true; /* ok */
    16681674
    }
    16691675

    @@ -1683,18 +1689,17 @@ Datum
    16831689
    json_typeof(PG_FUNCTION_ARGS)
    16841690
    {
    16851691
    text *json = PG_GETARG_TEXT_PP(0);
    1686-
    JsonLexContext *lex = makeJsonLexContext(json, false);
    1692+
    JsonLexContext lex;
    16871693
    char *type;
    1688-
    JsonTokenType tok;
    16891694
    JsonParseErrorType result;
    16901695

    16911696
    /* Lex exactly one token from the input and check its type. */
    1692-
    result = json_lex(lex);
    1697+
    makeJsonLexContext(&lex, json, false);
    1698+
    result = json_lex(&lex);
    16931699
    if (result != JSON_SUCCESS)
    1694-
    json_errsave_error(result, lex, NULL);
    1695-
    tok = lex->token_type;
    1700+
    json_errsave_error(result, &lex, NULL);
    16961701

    1697-
    switch (tok)
    1702+
    switch (lex.token_type)
    16981703
    {
    16991704
    case JSON_TOKEN_OBJECT_START:
    17001705
    type = "object";
    @@ -1716,7 +1721,7 @@ json_typeof(PG_FUNCTION_ARGS)
    17161721
    type = "null";
    17171722
    break;
    17181723
    default:
    1719-
    elog(ERROR, "unexpected json token: %d", tok);
    1724+
    elog(ERROR, "unexpected json token: %d", lex.token_type);
    17201725
    }
    17211726

    17221727
    PG_RETURN_TEXT_P(cstring_to_text(type));

    ‎src/backend/utils/adt/jsonb.c

    Lines changed: 7 additions & 6 deletions
    Original file line numberDiff line numberDiff line change
    @@ -252,13 +252,13 @@ jsonb_typeof(PG_FUNCTION_ARGS)
    252252
    static inline Datum
    253253
    jsonb_from_cstring(char *json, int len, bool unique_keys, Node *escontext)
    254254
    {
    255-
    JsonLexContext *lex;
    255+
    JsonLexContext lex;
    256256
    JsonbInState state;
    257257
    JsonSemAction sem;
    258258

    259259
    memset(&state, 0, sizeof(state));
    260260
    memset(&sem, 0, sizeof(sem));
    261-
    lex = makeJsonLexContextCstringLen(json, len, GetDatabaseEncoding(), true);
    261+
    makeJsonLexContextCstringLen(&lex, json, len, GetDatabaseEncoding(), true);
    262262

    263263
    state.unique_keys = unique_keys;
    264264
    state.escontext = escontext;
    @@ -271,7 +271,7 @@ jsonb_from_cstring(char *json, int len, bool unique_keys, Node *escontext)
    271271
    sem.scalar = jsonb_in_scalar;
    272272
    sem.object_field_start = jsonb_in_object_field_start;
    273273

    274-
    if (!pg_parse_json_or_errsave(lex, &sem, escontext))
    274+
    if (!pg_parse_json_or_errsave(&lex, &sem, escontext))
    275275
    return (Datum) 0;
    276276

    277277
    /* after parsing, the item member has the composed jsonb structure */
    @@ -755,11 +755,11 @@ datum_to_jsonb_internal(Datum val, bool is_null, JsonbInState *result,
    755755
    case JSONTYPE_JSON:
    756756
    {
    757757
    /* parse the json right into the existing result object */
    758-
    JsonLexContext *lex;
    758+
    JsonLexContext lex;
    759759
    JsonSemAction sem;
    760760
    text *json = DatumGetTextPP(val);
    761761

    762-
    lex = makeJsonLexContext(json, true);
    762+
    makeJsonLexContext(&lex, json, true);
    763763

    764764
    memset(&sem, 0, sizeof(sem));
    765765

    @@ -772,7 +772,8 @@ datum_to_jsonb_internal(Datum val, bool is_null, JsonbInState *result,
    772772
    sem.scalar = jsonb_in_scalar;
    773773
    sem.object_field_start = jsonb_in_object_field_start;
    774774

    775-
    pg_parse_json_or_ereport(lex, &sem);
    775+
    pg_parse_json_or_ereport(&lex, &sem);
    776+
    freeJsonLexContext(&lex);
    776777
    }
    777778
    break;
    778779
    case JSONTYPE_JSONB:

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