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Fix Shard Pruning Problem With Subqueries on VARCHAR Partition Columns 

Fixes #375

Prior to this change, shard pruning couldn't be done if:
- Table is hash-distributed
- Partition column of is VARCHAR
- Query to be pruned is a subquery

There were two problems:
- A bug in left-side/right-side checks for the partition column
- We were not considering relabeled types (VARCHAR was relabeled as TEXT)
pull/426/head
eren 2016-04-01 15:42:26 +03:00 committed by Jason Petersen
parent 339e1364d5
commit 1ffc30d7f5
No known key found for this signature in database
GPG Key ID: 9F1D3510D110ABA9
3 changed files with 85 additions and 8 deletions
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22
src/backend/distributed/planner/multi_logical_optimizer.c
View File

@ -3710,6 +3710,8 @@ PartitionColumnOpExpressionList(Query *query)
Node *whereNode = (Node *) lfirst(whereClauseCell);
Node *leftArgument = NULL;
Node *rightArgument = NULL;
Node *strippedLeftArgument = NULL;
Node *strippedRightArgument = NULL;
OpExpr *whereClause = NULL;
List *argumentList = NIL;
List *rangetableList = NIL;
@ -3744,14 +3746,16 @@ PartitionColumnOpExpressionList(Query *query)
leftArgument = (Node *) linitial(argumentList);
rightArgument = (Node *) lsecond(argumentList);
strippedLeftArgument = strip_implicit_coercions(leftArgument);
strippedRightArgument = strip_implicit_coercions(rightArgument);
if (IsA(leftArgument, Var) && IsA(rightArgument, Const))
if (IsA(strippedLeftArgument, Var) && IsA(strippedRightArgument, Const))
{
candidatePartitionColumn = (Var *) leftArgument;
candidatePartitionColumn = (Var *) strippedLeftArgument;
}
else if (IsA(leftArgument, Const) && IsA(leftArgument, Var))
else if (IsA(strippedLeftArgument, Const) && IsA(strippedRightArgument, Var))
{
candidatePartitionColumn = (Var *) rightArgument;
candidatePartitionColumn = (Var *) strippedRightArgument;
}
else
{
@ -3798,14 +3802,16 @@ ReplaceColumnsInOpExpressionList(List *opExpressionList, Var *newColumn)
Node *leftArgument = (Node *) linitial(argumentList);
Node *rightArgument = (Node *) lsecond(argumentList);
Node *strippedLeftArgument = strip_implicit_coercions(leftArgument);
Node *strippedRightArgument = strip_implicit_coercions(rightArgument);
if (IsA(leftArgument, Var))
if (IsA(strippedLeftArgument, Var))
{
newArgumentList = list_make2(newColumn, rightArgument);
newArgumentList = list_make2(newColumn, strippedRightArgument);
}
else if (IsA(leftArgument, Var))
else if (IsA(strippedRightArgument, Var))
{
newArgumentList = list_make2(leftArgument, newColumn);
newArgumentList = list_make2(strippedLeftArgument, newColumn);
}
copyOpExpression->args = newArgumentList;

28
src/test/regress/input/multi_subquery.source
View File

@ -294,3 +294,31 @@ FROM
l_orderkey = o_orderkey
GROUP BY
l_orderkey) AS unit_prices;
-- Check that we can prune shards in subqueries with VARCHAR partition columns
CREATE TABLE subquery_pruning_varchar_test_table
(
a varchar,
b int
);
SELECT master_create_distributed_table('subquery_pruning_varchar_test_table', 'a', 'hash');
SELECT master_create_worker_shards('subquery_pruning_varchar_test_table', 4, 1);
SET citus.subquery_pushdown TO TRUE;
SET client_min_messages TO DEBUG2;
SELECT * FROM
(SELECT count(*) FROM subquery_pruning_varchar_test_table WHERE a = 'onder' GROUP BY a)
AS foo;
SELECT * FROM
(SELECT count(*) FROM subquery_pruning_varchar_test_table WHERE 'eren' = a GROUP BY a)
AS foo;
SET client_min_messages TO NOTICE;
DROP TABLE subquery_pruning_varchar_test_table;
ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 102026;

43
src/test/regress/output/multi_subquery.source
View File

@ -326,3 +326,46 @@ FROM
l_orderkey) AS unit_prices;
ERROR: cannot push down this subquery
DETAIL: Shards of relations in subquery need to have 1-to-1 shard partitioning
-- Check that we can prune shards in subqueries with VARCHAR partition columns
CREATE TABLE subquery_pruning_varchar_test_table
(
a varchar,
b int
);
SELECT master_create_distributed_table('subquery_pruning_varchar_test_table', 'a', 'hash');
master_create_distributed_table
---------------------------------
(1 row)
SELECT master_create_worker_shards('subquery_pruning_varchar_test_table', 4, 1);
master_create_worker_shards
-----------------------------
(1 row)
SET citus.subquery_pushdown TO TRUE;
SET client_min_messages TO DEBUG2;
SELECT * FROM
(SELECT count(*) FROM subquery_pruning_varchar_test_table WHERE a = 'onder' GROUP BY a)
AS foo;
DEBUG: predicate pruning for shardId 102029
DEBUG: predicate pruning for shardId 102027
DEBUG: predicate pruning for shardId 102026
count
-------
(0 rows)
SELECT * FROM
(SELECT count(*) FROM subquery_pruning_varchar_test_table WHERE 'eren' = a GROUP BY a)
AS foo;
DEBUG: predicate pruning for shardId 102029
DEBUG: predicate pruning for shardId 102028
DEBUG: predicate pruning for shardId 102026
count
-------
(0 rows)
SET client_min_messages TO NOTICE;
DROP TABLE subquery_pruning_varchar_test_table;
ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 102026;