Merge pull request ClickHouse#79401 from ClickHouse/pr-lazy-materialization

Lazy Materialization with parallel replicas

Author: devcrafter

src/Processors/QueryPlan/Optimizations/optimizeLazyMaterialization.cpp

@@ -25,9 +25,6 @@ static bool canUseLazyMaterializationForReadingStep(ReadFromMergeTree * reading)
     if (reading->isQueryWithSampling())
         return false;
 
-    if (reading->isParallelReadingEnabled())
-        return false;
-
     return true;
 }
 

tests/queries/0_stateless/03443_pr_lazy_materialization.reference

@@ -0,0 +1,11 @@
+LazilyRead (Lazily Read)
+0	
+1	blob_
+2	blob_blob_
+3	blob_blob_blob_
+4	blob_blob_blob_blob_
+5	blob_blob_blob_blob_blob_
+6	blob_blob_blob_blob_blob_blob_
+7	blob_blob_blob_blob_blob_blob_blob_
+8	blob_blob_blob_blob_blob_blob_blob_blob_
+9	blob_blob_blob_blob_blob_blob_blob_blob_blob_

tests/queries/0_stateless/03443_pr_lazy_materialization.sql

@@ -0,0 +1,24 @@
+DROP TABLE IF EXISTS pr_tt;
+CREATE TABLE pr_tt (k UInt64, v String, blob String) ENGINE=MergeTree() ORDER BY tuple() settings index_granularity=100;
+INSERT INTO pr_tt SELECT number, toString(number), repeat('blob_', number % 10) FROM numbers(1_000_000);
+
+-- make sure the optimization is enabled
+set query_plan_optimize_lazy_materialization=true, query_plan_max_limit_for_lazy_materialization=10;
+SET enable_parallel_replicas = 1, cluster_for_parallel_replicas = 'test_cluster_one_shard_three_replicas_localhost', parallel_replicas_for_non_replicated_merge_tree = 1;
+
+select trimLeft(explain) as s from (EXPLAIN
+SELECT
+    v,
+    blob
+FROM pr_tt
+ORDER BY k ASC
+LIMIT 10 settings parallel_replicas_local_plan=1) where s ilike 'LazilyRead%';
+
+SELECT
+    v,
+    blob
+FROM pr_tt
+ORDER BY k
+LIMIT 10;
+
+DROP TABLE pr_tt;