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Add 'ignore_nulls' option to row_to_json

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Provide an option to skip NULL values in a row when generating a JSON
object from that row with row_to_json.  This can reduce the size of the
JSON object in cases where columns are NULL without really reducing the
information in the JSON object.

This also makes row_to_json into a single function with default values,
rather than having multiple functions.  In passing, change array_to_json
to also be a single function with default values (we don't add an
'ignore_nulls' option yet- it's not clear that there is a sensible
use-case there, and it hasn't been asked for in any case).

Pavel Stehule
This commit is contained in:
Stephen Frost
2014-09-11 21:23:51 -04:00
parent c3c75fcd7a
commit 95d737ff45
8 changed files with 118 additions and 51 deletions
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55
src/backend/utils/adt/json.c
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@ -79,7 +79,8 @@ static void report_invalid_token(JsonLexContext *lex);
static int report_json_context(JsonLexContext *lex);
static char *extract_mb_char(char *s);
static void composite_to_json(Datum composite, StringInfo result,
bool use_line_feeds);
bool use_line_feeds,
bool ignore_nulls);
static void array_dim_to_json(StringInfo result, int dim, int ndims, int *dims,
Datum *vals, bool *nulls, int *valcount,
JsonTypeCategory tcategory, Oid outfuncoid,
@ -1362,7 +1363,7 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
array_to_json_internal(val, result, false);
break;
case JSONTYPE_COMPOSITE:
composite_to_json(val, result, false);
composite_to_json(val, result, false, false);
break;
case JSONTYPE_BOOL:
outputstr = DatumGetBool(val) ? "true" : "false";
@ -1591,7 +1592,8 @@ array_to_json_internal(Datum array, StringInfo result, bool use_line_feeds)
* Turn a composite / record into JSON.
*/
static void
composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
composite_to_json(Datum composite, StringInfo result, bool use_line_feeds,
bool ignore_nulls)
{
HeapTupleHeader td;
Oid tupType;
@ -1630,6 +1632,12 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
if (tupdesc->attrs[i]->attisdropped)
continue;
val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
/* Don't serialize NULL field when we don't want it */
if (isnull && ignore_nulls)
continue;
if (needsep)
appendStringInfoString(result, sep);
needsep = true;
@ -1638,8 +1646,6 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
escape_json(result, attname);
appendStringInfoChar(result, ':');
val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
if (isnull)
{
tcategory = JSONTYPE_NULL;
@ -1687,27 +1693,11 @@ add_json(Datum val, bool is_null, StringInfo result,
datum_to_json(val, is_null, result, tcategory, outfuncoid, key_scalar);
}
/*
* SQL function array_to_json(row)
*/
extern Datum
array_to_json(PG_FUNCTION_ARGS)
{
Datum array = PG_GETARG_DATUM(0);
StringInfo result;
result = makeStringInfo();
array_to_json_internal(array, result, false);
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
}
/*
* SQL function array_to_json(row, prettybool)
*/
extern Datum
array_to_json_pretty(PG_FUNCTION_ARGS)
array_to_json(PG_FUNCTION_ARGS)
{
Datum array = PG_GETARG_DATUM(0);
bool use_line_feeds = PG_GETARG_BOOL(1);
@ -1721,34 +1711,19 @@ array_to_json_pretty(PG_FUNCTION_ARGS)
}
/*
* SQL function row_to_json(row)
* SQL function row_to_json(rowval record, pretty bool, ignore_nulls bool)
*/
extern Datum
row_to_json(PG_FUNCTION_ARGS)
{
Datum array = PG_GETARG_DATUM(0);
StringInfo result;
result = makeStringInfo();
composite_to_json(array, result, false);
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
}
/*
* SQL function row_to_json(row, prettybool)
*/
extern Datum
row_to_json_pretty(PG_FUNCTION_ARGS)
{
Datum array = PG_GETARG_DATUM(0);
bool use_line_feeds = PG_GETARG_BOOL(1);
bool ignore_nulls = PG_GETARG_BOOL(2);
StringInfo result;
result = makeStringInfo();
composite_to_json(array, result, use_line_feeds);
composite_to_json(array, result, use_line_feeds, ignore_nulls);
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
}