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SQL/JSON: support the IS JSON predicate

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This patch introduces the SQL standard IS JSON predicate. It operates
on text and bytea values representing JSON, as well as on the json and
jsonb types. Each test has IS and IS NOT variants and supports a WITH
UNIQUE KEYS flag. The tests are:

IS JSON [VALUE]
IS JSON ARRAY
IS JSON OBJECT
IS JSON SCALAR

These should be self-explanatory.

The WITH UNIQUE KEYS flag makes these return false when duplicate keys
exist in any object within the value, not necessarily directly contained
in the outermost object.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/CAF4Au4w2x-5LTnN_bxky-mq4=WOqsGsxSpENCzHRAzSnEd8+WQ@mail.gmail.com
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
This commit is contained in:
Alvaro Herrera
2023-03-31 22:34:04 +02:00
parent a2a0c7c29e
commit 6ee30209a6
25 changed files with 1031 additions and 68 deletions
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132
src/backend/utils/adt/json.c
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@ -62,6 +62,23 @@ typedef struct JsonUniqueHashEntry
int object_id;
} JsonUniqueHashEntry;
/* Stack element for key uniqueness check during JSON parsing */
typedef struct JsonUniqueStackEntry
{
struct JsonUniqueStackEntry *parent;
int object_id;
} JsonUniqueStackEntry;
/* Context struct for key uniqueness check during JSON parsing */
typedef struct JsonUniqueParsingState
{
JsonLexContext *lex;
JsonUniqueCheckState check;
JsonUniqueStackEntry *stack;
int id_counter;
bool unique;
} JsonUniqueParsingState;
/* Context struct for key uniqueness check during JSON building */
typedef struct JsonUniqueBuilderState
{
@ -1648,6 +1665,110 @@ escape_json(StringInfo buf, const char *str)
appendStringInfoCharMacro(buf, '"');
}
/* Semantic actions for key uniqueness check */
static JsonParseErrorType
json_unique_object_start(void *_state)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return JSON_SUCCESS;
/* push object entry to stack */
entry = palloc(sizeof(*entry));
entry->object_id = state->id_counter++;
entry->parent = state->stack;
state->stack = entry;
return JSON_SUCCESS;
}
static JsonParseErrorType
json_unique_object_end(void *_state)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return JSON_SUCCESS;
entry = state->stack;
state->stack = entry->parent; /* pop object from stack */
pfree(entry);
return JSON_SUCCESS;
}
static JsonParseErrorType
json_unique_object_field_start(void *_state, char *field, bool isnull)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return JSON_SUCCESS;
/* find key collision in the current object */
if (json_unique_check_key(&state->check, field, state->stack->object_id))
return JSON_SUCCESS;
state->unique = false;
/* pop all objects entries */
while ((entry = state->stack))
{
state->stack = entry->parent;
pfree(entry);
}
return JSON_SUCCESS;
}
/* Validate JSON text and additionally check key uniqueness */
bool
json_validate(text *json, bool check_unique_keys, bool throw_error)
{
JsonLexContext *lex = makeJsonLexContext(json, check_unique_keys);
JsonSemAction uniqueSemAction = {0};
JsonUniqueParsingState state;
JsonParseErrorType result;
if (check_unique_keys)
{
state.lex = lex;
state.stack = NULL;
state.id_counter = 0;
state.unique = true;
json_unique_check_init(&state.check);
uniqueSemAction.semstate = &state;
uniqueSemAction.object_start = json_unique_object_start;
uniqueSemAction.object_field_start = json_unique_object_field_start;
uniqueSemAction.object_end = json_unique_object_end;
}
result = pg_parse_json(lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
if (result != JSON_SUCCESS)
{
if (throw_error)
json_errsave_error(result, lex, NULL);
return false; /* invalid json */
}
if (check_unique_keys && !state.unique)
{
if (throw_error)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_JSON_OBJECT_KEY_VALUE),
errmsg("duplicate JSON object key value")));
return false; /* not unique keys */
}
return true; /* ok */
}
/*
* SQL function json_typeof(json) -> text
*
@ -1663,21 +1784,18 @@ escape_json(StringInfo buf, const char *str)
Datum
json_typeof(PG_FUNCTION_ARGS)
{
text *json;
JsonLexContext *lex;
JsonTokenType tok;
text *json = PG_GETARG_TEXT_PP(0);
JsonLexContext *lex = makeJsonLexContext(json, false);
char *type;
JsonTokenType tok;
JsonParseErrorType result;
json = PG_GETARG_TEXT_PP(0);
lex = makeJsonLexContext(json, false);
/* Lex exactly one token from the input and check its type. */
result = json_lex(lex);
if (result != JSON_SUCCESS)
json_errsave_error(result, lex, NULL);
tok = lex->token_type;
switch (tok)
{
case JSON_TOKEN_OBJECT_START: