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IS JSON predicate

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This patch intrdocuces 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 an IS and IS NOT variant. The tests are:

IS JSON [VALUE]
IS JSON ARRAY
IS JSON OBJECT
IS JSON SCALAR
IS JSON  WITH | WITHOUT UNIQUE KEYS

These are mostly self-explanatory, but note that IS JSON WITHOUT UNIQUE
KEYS is true whenever IS JSON is true, and IS JSON WITH UNIQUE KEYS is
true whenever IS JSON is true except it IS JSON OBJECT is true and there
are duplicate keys (which is never the case when applied to jsonb values).

Nikita Glukhov

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/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
This commit is contained in:
Andrew Dunstan
2022-03-03 13:02:53 -05:00
parent 6198420ad8
commit 33a377608f
25 changed files with 856 additions and 17 deletions
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105
src/backend/utils/adt/json.c
View File

@@ -13,6 +13,7 @@
*/
#include "postgres.h"
#include "access/hash.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "common/hashfn.h"
@@ -1655,6 +1656,94 @@ escape_json(StringInfo buf, const char *str)
appendStringInfoCharMacro(buf, '"');
}
/* Semantic actions for key uniqueness check */
static void
json_unique_object_start(void *_state)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return;
/* push object entry to stack */
entry = palloc(sizeof(*entry));
entry->object_id = state->id_counter++;
entry->parent = state->stack;
state->stack = entry;
}
static void
json_unique_object_end(void *_state)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return;
entry = state->stack;
state->stack = entry->parent; /* pop object from stack */
pfree(entry);
}
static void
json_unique_object_field_start(void *_state, char *field, bool isnull)
{
JsonUniqueParsingState *state = _state;
JsonUniqueStackEntry *entry;
if (!state->unique)
return;
/* find key collision in the current object */
if (json_unique_check_key(&state->check, field, state->stack->object_id))
return;
state->unique = false;
/* pop all objects entries */
while ((entry = state->stack))
{
state->stack = entry->parent;
pfree(entry);
}
}
/* Validate JSON text and additionally check key uniqueness */
bool
json_validate(text *json, bool check_unique_keys)
{
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)
return false; /* invalid json */
if (check_unique_keys && !state.unique)
return false; /* not unique keys */
return true; /* ok */
}
/*
* SQL function json_typeof(json) -> text
*
@@ -1670,21 +1759,13 @@ 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);
char *type;
JsonParseErrorType result;
json = PG_GETARG_TEXT_PP(0);
lex = makeJsonLexContext(json, false);
JsonTokenType tok;
/* Lex exactly one token from the input and check its type. */
result = json_lex(lex);
if (result != JSON_SUCCESS)
json_ereport_error(result, lex);
tok = lex->token_type;
tok = json_get_first_token(json, true);
switch (tok)
{
case JSON_TOKEN_OBJECT_START: