Function cdbexplain_sendExecStats

src/backend/commands/explain_gp.c:383–467

* cdbexplain_sendExecStats * Called by qExec process to send EXPLAIN ANALYZE statistics to qDisp. * On the qDisp, libpq will recognize our special message type ('Y') and * attach the message to the current command's PGresult object. */

 *	  attach the message to the current command's PGresult object.
 */
void
cdbexplain_sendExecStats(QueryDesc *queryDesc)
{
	EState	   *estate;
	PlanState  *planstate;
	CdbExplain_SendStatCtx ctx;
	StringInfoData notebuf;

	/* Header offset (where header begins in the message buffer) */
	int			hoff;

	Assert(Gp_role == GP_ROLE_EXECUTE);

	if (!queryDesc ||
		!queryDesc->estate)
		return;

	/* If executing a root slice (UPD/DEL/INS), start at top of plan tree. */
	estate = queryDesc->estate;
	if (LocallyExecutingSliceIndex(estate) == RootSliceIndex(estate))
		planstate = queryDesc->planstate;

	/* Non-root slice: Start at child of our sending Motion node. */
	else
	{
		planstate = &(getMotionState(queryDesc->planstate, LocallyExecutingSliceIndex(estate))->ps);
		Assert(planstate &&
			   IsA(planstate, MotionState) &&
			   planstate->lefttree);
		planstate = planstate->lefttree;
	}

	if (planstate == NULL)
		return;

	/* Start building the message header in our context area. */
	memset(&ctx, 0, sizeof(ctx));
	ctx.hdr.type = T_CdbExplain_StatHdr;
	ctx.hdr.segindex = GpIdentity.segindex;
	ctx.hdr.nInst = 0;

	/* Allocate a separate buffer where nodes can append extra message text. */
	initStringInfo(&notebuf);
	ctx.notebuf = &notebuf;

	/* Reserve buffer space for the message header (excluding 'inst' array). */
	pq_beginmessage(&ctx.buf, 'Y');

	/* Where the actual StatHdr begins */
	hoff = ctx.buf.len;

	/*
	 * Write everything until inst member including "CdbExplain_SliceWorker
	 * worker"
	 */
	appendBinaryStringInfo(&ctx.buf, (char *) &ctx.hdr, sizeof(ctx.hdr) - sizeof(ctx.hdr.inst));

	/* Append statistics from each PlanState node in this slice. */