Function ExplainParallelRetrieveCursor

src/backend/commands/explain_gp.c:2308–2361

* Explain a parallel retrieve cursor, * indicate the endpoints exist on entry DB, or on some segments, * or on all segments. */

 * or on all segments.
 */
void ExplainParallelRetrieveCursor(ExplainState *es, QueryDesc* queryDesc)
{
	PlannedStmt *plan = queryDesc->plannedstmt;
	SliceTable *sliceTable = queryDesc->estate->es_sliceTable;
	StringInfoData            endpointInfoStr;
	enum EndPointExecPosition endPointExecPosition;

	initStringInfo(&endpointInfoStr);

	endPointExecPosition = GetParallelCursorEndpointPosition(plan);
	ExplainOpenGroup("Cursor", "Cursor", true, es);
	switch(endPointExecPosition)
	{
		case ENDPOINT_ON_ENTRY_DB:
		{
			appendStringInfo(&endpointInfoStr, "\"on coordinator\"");
			break;
		}
		case ENDPOINT_ON_SINGLE_QE:
		{
			appendStringInfo(
							 &endpointInfoStr, "\"on segment: contentid [%d]\"",
							 gp_session_id % plan->planTree->flow->numsegments);
			break;
		}
		case ENDPOINT_ON_SOME_QE:
		{
			ListCell * cell;
			bool isFirst = true;
			appendStringInfo(&endpointInfoStr, "on segments: contentid [");
			ExecSlice *slice = &sliceTable->slices[0];
			foreach(cell, slice->segments)
			{
				int contentid = lfirst_int(cell);
				appendStringInfo(&endpointInfoStr, (isFirst)?"%d":", %d", contentid);
				isFirst = false;
			}
			appendStringInfo(&endpointInfoStr, "]");
			break;
		}
		case ENDPOINT_ON_ALL_QE:
		{
			appendStringInfo(&endpointInfoStr, "on all %d segments", getgpsegmentCount());
			break;
		}
		default:
		{
			elog(ERROR, "invalid endpoint position : %d", endPointExecPosition);
			break;
		}
	}
	ExplainPropertyText("Endpoint", endpointInfoStr.data, es);
	ExplainCloseGroup("Cursor", "Cursor", true, es);
}