Function DensifyPartitionCore

pg_documentdb/src/aggregation/bson_densify.c:785–854

* Core implementation of generating documents for densify. Currently this supports both * `range` and `partition` mode of densify. */

 * `range` and `partition` mode of densify.
 */
static pgbson *
DensifyPartitionCore(PG_FUNCTION_ARGS, DensifyType type)
{
	WindowObject winObject = PG_WINDOW_OBJECT();

	bool isNull = false;
	pgbson *spec = DatumGetPgBson(WinGetFuncArgCurrent(winObject, 1, &isNull));

	DensifyWindowState *densifyState = NULL;
	int argPosition = 1;
	SetCachedFunctionState(
		densifyState,
		DensifyWindowState,
		argPosition,
		InitializeDensifyWindowState,
		spec,
		type);

	if (densifyState == NULL)
	{
		densifyState = palloc0(sizeof(DensifyWindowState));
		InitializeDensifyWindowState(densifyState, spec, type);
	}

	pgbson *document = NULL;
	isNull = false;
	Datum documentDatum = WinGetFuncArgCurrent(winObject, 0, &isNull);
	if (isNull)
	{
		if (type == DENSIFY_TYPE_RANGE &&
			densifyState->previousType == DENSIFY_DOCUMENT_VALID)
		{
			/*
			 * Ignore this row because NULL row is added via a UNION
			 * query to help generate documents in case of:
			 *     - Non existing collection.
			 *     - Empty collection.
			 *     - Filtered collection with 0 rows.
			 */
			return NULL;
		}
	}
	else
	{
		document = DatumGetPgBson(documentDatum);
	}

	densifyState->previousType = isNull ? DENSIFY_DOCUMENT_NULL : DENSIFY_DOCUMENT_VALID;

	PartitionAwareState *partitionState = GetValidPartitionAwareState(densifyState,
																	  document);

	/* Check if this is the last row in the partition */
	bool isOut = false;
	isNull = false;
	WinGetFuncArgInPartition(winObject, 1, 1, WINDOW_SEEK_CURRENT, false,
							 &isNull, &isOut);
	partitionState->isLastRow = isOut;