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Don't distribute single execution queries

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Summary:
Queries such as `RETURN 1` should only be run on a single machine. This
change assumes that a query should only be distributed if it contains at
least one `ScanAll` operator, i.e. a `MATCH` clause.

Reviewers: florijan, msantl

Reviewed By: msantl

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1154
This commit is contained in:
Teon Banek 2018-01-29 14:51:12 +01:00
parent 3f30a6fad9
commit 471d63ad86
2 changed files with 16 additions and 8 deletions
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22
src/query/plan/distributed.cpp
View File

@ -39,6 +39,14 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
using HierarchicalLogicalOperatorVisitor::PostVisit;
using HierarchicalLogicalOperatorVisitor::PreVisit;
// Returns true if the plan should be run on master and workers. Note, that
// false is returned if the plan is already split.
bool ShouldSplit() {
// At the moment, the plan should be run on workers only if we encountered a
// ScanAll.
return !distributed_plan_.worker_plan && has_scan_all_;
}
// ScanAll are all done on each machine locally.
bool PreVisit(ScanAll &) override { return true; }
bool PostVisit(ScanAll &) override {
@ -93,7 +101,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
// 2) Worker plan with operators below Skip, but without Skip itself.
bool PreVisit(Skip &) override { return true; }
bool PostVisit(Skip &skip) override {
if (!distributed_plan_.worker_plan) {
if (ShouldSplit()) {
auto input = skip.input();
distributed_plan_.worker_plan = input;
skip.set_input(std::make_shared<PullRemote>(
@ -110,7 +118,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
// 2) Worker plan with operators below Limit, but including Limit itself.
bool PreVisit(Limit &) override { return true; }
bool PostVisit(Limit &limit) override {
if (!distributed_plan_.worker_plan) {
if (ShouldSplit()) {
// Shallow copy Limit
distributed_plan_.worker_plan = std::make_shared<Limit>(limit);
auto input = limit.input();
@ -127,7 +135,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
bool PreVisit(OrderBy &) override { return true; }
bool PostVisit(OrderBy &order_by) override {
// TODO: Associative combination of OrderBy
if (!distributed_plan_.worker_plan) {
if (ShouldSplit()) {
auto input = order_by.input();
distributed_plan_.worker_plan = input;
order_by.set_input(std::make_shared<PullRemote>(
@ -140,7 +148,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
// Treat Distinct just like Limit.
bool PreVisit(Distinct &) override { return true; }
bool PostVisit(Distinct &distinct) override {
if (!distributed_plan_.worker_plan) {
if (ShouldSplit()) {
// Shallow copy Distinct
distributed_plan_.worker_plan = std::make_shared<Distinct>(distinct);
auto input = distinct.input();
@ -167,7 +175,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
// completely done on master.
bool PreVisit(Aggregate &) override { return true; }
bool PostVisit(Aggregate &aggr_op) override {
if (distributed_plan_.worker_plan) {
if (!ShouldSplit()) {
// We have already split the plan, so the aggregation we are visiting is
// on master.
return true;
@ -308,7 +316,7 @@ class DistributedPlanner : public HierarchicalLogicalOperatorVisitor {
if (!master_aggr_) return true;
// We have to rewire master/worker aggregation.
DCHECK(worker_aggr_);
DCHECK(!distributed_plan_.worker_plan);
DCHECK(ShouldSplit());
DCHECK(std::dynamic_pointer_cast<Aggregate>(produce.input()));
distributed_plan_.worker_plan = std::move(worker_aggr_);
produce.set_input(std::move(master_aggr_));
@ -360,7 +368,7 @@ DistributedPlan MakeDistributedPlan(const LogicalOperator &original_plan,
Clone(original_plan);
DistributedPlanner planner(distributed_plan);
distributed_plan.master_plan->Accept(planner);
if (!distributed_plan.worker_plan) {
if (planner.ShouldSplit()) {
// We haven't split the plan, this means that it should be the same on
// master and worker. We only need to prepend PullRemote to master plan.
distributed_plan.worker_plan = std::move(distributed_plan.master_plan);

2
tests/manual/query_planner.cpp
View File

@ -617,7 +617,7 @@ DEFCOMMAND(ShowDistributed) {
distributed_plan.master_plan->Accept(printer);
std::cout << std::endl;
}
{
if (distributed_plan.worker_plan) {
std::cout << "---- Worker Plan ---- " << std::endl;
PlanPrinter printer(dba);
distributed_plan.worker_plan->Accept(printer);