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Allow auto distributed_group_by_no_merge for DISTINCT of sharding key

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This commit is contained in:
Azat Khuzhin 2020-04-19 18:47:33 +03:00
parent de4a723264
commit 93d049fe64
2 changed files with 35 additions and 13 deletions
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24
src/Storages/StorageDistributed.cpp
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@ -383,6 +383,7 @@ StoragePtr StorageDistributed::createWithOwnCluster(
bool StorageDistributed::canForceGroupByNoMerge(const Context &context, const ASTPtr & query_ptr) const
{
const auto & settings = context.getSettingsRef();
std::string reason;
if (settings.distributed_group_by_no_merge)
return true;
@ -395,8 +396,20 @@ bool StorageDistributed::canForceGroupByNoMerge(const Context &context, const AS
if (select.orderBy())
return false;
if (select.distinct)
{
for (auto & expr : select.select()->children)
{
auto id = expr->as<ASTIdentifier>();
if (!id)
return false;
if (!sharding_key_expr->getSampleBlock().has(id->name))
return false;
}
reason = "DISTINCT " + backQuote(serializeAST(*select.select(), true));
}
// This can use distributed_group_by_no_merge but in this case limit stage
// should be done later (which is not the case right now).
@ -405,8 +418,12 @@ bool StorageDistributed::canForceGroupByNoMerge(const Context &context, const AS
const ASTPtr group_by = select.groupBy();
if (!group_by)
{
if (!select.distinct)
return false;
}
else
{
// injective functions are optimized out in optimizeGroupBy()
// hence all we need to check is that column in GROUP BY matches sharding expression
auto & group_exprs = group_by->children;
@ -419,7 +436,10 @@ bool StorageDistributed::canForceGroupByNoMerge(const Context &context, const AS
if (!sharding_key_expr->getSampleBlock().has(id->name))
return false;
LOG_DEBUG(log, "Force distributed_group_by_no_merge for GROUP BY " << backQuote(serializeAST(*group_by, true)) << " (injective)");
reason = "GROUP BY " + backQuote(serializeAST(*group_by, true));
}
LOG_DEBUG(log, "Force distributed_group_by_no_merge for " << reason << " (injective)");
return true;
}

2
tests/queries/0_stateless/01247_distributed_group_by_no_merge_GROUP_BY_injective_sharding_key.reference
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@ -41,6 +41,8 @@ countDistinct GROUP BY number
DISTINCT
0
1
0
1
HAVING
LIMIT
2 0