/*
* cdbpathtoplan_create_flow
*/
Flow *
cdbpathtoplan_create_flow(PlannerInfo *root,
CdbPathLocus locus,
Relids relids,
List *pathkeys,
Plan *plan)
{
Flow *flow = NULL;
/* Distribution */
if (CdbPathLocus_IsEntry(locus))
{
flow = makeFlow(FLOW_SINGLETON);
flow->segindex = -1;
}
else if (CdbPathLocus_IsSingleQE(locus))
{
flow = makeFlow(FLOW_SINGLETON);
flow->segindex = 0;
}
else if (CdbPathLocus_IsGeneral(locus))
{
flow = makeFlow(FLOW_SINGLETON);
flow->segindex = 0;
}
else if (CdbPathLocus_IsReplicated(locus))
{
flow = makeFlow(FLOW_REPLICATED);
}
else if (CdbPathLocus_IsHashed(locus) ||
CdbPathLocus_IsHashedOJ(locus))
{
flow = makeFlow(FLOW_PARTITIONED);
flow->hashExpr = cdbpathlocus_get_partkey_exprs(locus,
relids,
plan->targetlist);
/*
* hashExpr can be NIL if the rel is partitioned on columns that aren't
* projected (i.e. are not present in the result of this Path operator).
*/
}
else if (CdbPathLocus_IsStrewn(locus))
flow = makeFlow(FLOW_PARTITIONED);
else
Insist(0);
/*
* Describe the ordering of the result rows. The ordering info will be
* truncated upon encountering an expr which is not already present in the
* plan's targetlist. Duplicate cols and constant cols will be omitted.
*/
if (pathkeys)
{
Sort *sort = make_sort_from_pathkeys(root, plan, pathkeys, relids, false);
if (sort)
{
flow->numSortCols = sort->numCols;
flow->sortColIdx = sort->sortColIdx;
flow->sortOperators = sort->sortOperators;
}
}
flow->req_move = MOVEMENT_NONE;
flow->locustype = locus.locustype;
return flow;
} /* cdbpathtoplan_create_flow */
/*
* cdbpath_create_motion_path
* Returns a Path that delivers the subpath result to the
* given locus, or NULL if it can't be done.
*
* 'pathkeys' must specify an ordering equal to or weaker than the
* subpath's existing ordering.
*
* If no motion is needed, the caller's subpath is returned unchanged.
* Else if require_existing_order is true, NULL is returned if the
* motion would not preserve an ordering at least as strong as the
* specified ordering; also NULL is returned if pathkeys is NIL
* meaning the caller is just checking and doesn't want to add motion.
* Else a CdbMotionPath is returned having either the specified pathkeys
* (if given and the motion uses Merge Receive), or the pathkeys
* of the original subpath (if the motion is order-preserving), or no
* pathkeys otherwise (the usual case).
*/
Path *
cdbpath_create_motion_path(PlannerInfo *root,
Path *subpath,
List *pathkeys,
bool require_existing_order,
CdbPathLocus locus)
{
CdbMotionPath *pathnode;
UnusedArg(root);
Assert(cdbpathlocus_is_valid(locus) &&
cdbpathlocus_is_valid(subpath->locus));
/* Moving subpath output to a single executor process (qDisp or qExec)? */
if (CdbPathLocus_IsBottleneck(locus))
{
/* entry-->entry or singleQE-->singleQE? No motion needed. */
if (CdbPathLocus_IsEqual(subpath->locus, locus))
return subpath;
/* entry-->singleQE? Don't move. Slice's QE will run on entry db. */
if (CdbPathLocus_IsEntry(subpath->locus))
return subpath;
/* singleQE-->entry? Don't move. Slice's QE will run on entry db. */
if (CdbPathLocus_IsSingleQE(subpath->locus))
{
/* Create CdbMotionPath node to indicate that the slice must be
* dispatched to a singleton gang running on the entry db. We
* merely use this node to note that the path has 'Entry' locus;
* no corresponding Motion node will be created in the Plan tree.
*/
Assert(CdbPathLocus_IsEntry(locus));
pathnode = makeNode(CdbMotionPath);
pathnode->path.pathtype = T_Motion;
pathnode->path.parent = subpath->parent;
pathnode->path.locus = locus;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
/* Costs, etc, are same as subpath. */
pathnode->path.startup_cost = subpath->total_cost;
pathnode->path.total_cost = subpath->total_cost;
pathnode->path.memory = subpath->memory;
pathnode->path.motionHazard = subpath->motionHazard;
pathnode->path.rescannable = subpath->rescannable;
return (Path *)pathnode;
}
/* No motion needed if subpath can run anywhere giving same output. */
if (CdbPathLocus_IsGeneral(subpath->locus))
return subpath;
/* Fail if caller refuses motion. */
if (require_existing_order &&
!pathkeys)
return NULL;
/* replicated-->singleton would give redundant copies of the rows. */
if (CdbPathLocus_IsReplicated(subpath->locus))
goto invalid_motion_request;
/* Must be partitioned-->singleton.
* If caller gave pathkeys, they'll be used for Merge Receive.
* If no pathkeys, Union Receive will arbitrarily interleave
* the rows from the subpath partitions in no special order.
*/
if (!CdbPathLocus_IsPartitioned(subpath->locus))
goto invalid_motion_request;
}
/* Output from a single process to be distributed over a gang? */
else if (CdbPathLocus_IsBottleneck(subpath->locus))
{
/* Must be bottleneck-->partitioned or bottleneck-->replicated */
if (!CdbPathLocus_IsPartitioned(locus) &&
!CdbPathLocus_IsReplicated(locus))
goto invalid_motion_request;
/* Fail if caller disallows motion. */
if (require_existing_order &&
!pathkeys)
return NULL;
/* Each qExec receives a subset of the rows, with ordering preserved. */
pathkeys = subpath->pathkeys;
}
/* Redistributing partitioned subpath output from one gang to another? */
else if (CdbPathLocus_IsPartitioned(subpath->locus))
{
/* partitioned-->partitioned? */
if (CdbPathLocus_IsPartitioned(locus))
{
/* No motion if subpath partitioning matches caller's request. */
if (cdbpathlocus_compare(CdbPathLocus_Comparison_Equal, subpath->locus, locus))
return subpath;
}
/* Must be partitioned-->replicated */
else if (!CdbPathLocus_IsReplicated(locus))
goto invalid_motion_request;
/* Fail if caller insists on ordered result or no motion. */
if (require_existing_order)
return NULL;
/* Output streams lose any ordering they had.
* Only a qDisp or singleton qExec can merge sorted streams (for now).
*/
pathkeys = NIL;
}
/* If subplan uses no tables, it can run on qDisp or a singleton qExec. */
else if (CdbPathLocus_IsGeneral(subpath->locus))
{
/* No motion needed if general-->general or general-->replicated. */
if (CdbPathLocus_IsGeneral(locus) ||
CdbPathLocus_IsReplicated(locus))
return subpath;
/* Must be general-->partitioned. */
if (!CdbPathLocus_IsPartitioned(locus))
goto invalid_motion_request;
/* Fail if caller wants no motion. */
if (require_existing_order &&
!pathkeys)
return NULL;
/* Since the motion is 1-to-many, the rows remain in the same order. */
pathkeys = subpath->pathkeys;
}
/* Does subpath produce same multiset of rows on every qExec of its gang? */
else if (CdbPathLocus_IsReplicated(subpath->locus))
{
/* No-op if replicated-->replicated. */
if (CdbPathLocus_IsReplicated(locus))
return subpath;
/* Other destinations aren't used or supported at present. */
goto invalid_motion_request;
}
else
goto invalid_motion_request;
/* Don't materialize before motion. */
if (IsA(subpath, MaterialPath))
subpath = ((MaterialPath *)subpath)->subpath;
/*
* MPP-3300: materialize *before* motion can never help us, motion
* pushes data. other nodes pull. We relieve motion deadlocks by
* adding materialize nodes on top of motion nodes
*/
/* Create CdbMotionPath node. */
pathnode = makeNode(CdbMotionPath);
pathnode->path.pathtype = T_Motion;
pathnode->path.parent = subpath->parent;
pathnode->path.locus = locus;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
/* Cost of motion */
cdbpath_cost_motion(root, pathnode);
/* Tell operators above us that slack may be needed for deadlock safety. */
pathnode->path.motionHazard = true;
pathnode->path.rescannable = false;
return (Path *)pathnode;
/* Unexpected source or destination locus. */
invalid_motion_request:
Assert(0);
return NULL;
} /* cdbpath_create_motion_path */
