Parallel Replicas

```
┌─message────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ (from 54.218.178.249:59198) SELECT * FROM session_events WHERE type='type2' LIMIT 10 SETTINGS allow_experimental_parallel_reading_from_replicas=2; (stage: Complete)                                                                                       │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') SETTINGS allow_experimental_parallel_reading_from_replicas = 2 to stage Complete │
│ Access granted: SELECT(clientId, sessionId, pageId, timestamp, type) ON default.session_events                                                                                                                                                             │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') to stage WithMergeableState only analyze │
│ Access granted: SELECT(clientId, sessionId, pageId, timestamp, type) ON default.session_events                                                                                                                                                             │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') from stage FetchColumns to stage WithMergeableState only analyze │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') SETTINGS allow_experimental_parallel_reading_from_replicas = 2 to stage WithMergeableState only analyze │
│ Access granted: SELECT(clientId, sessionId, pageId, timestamp, type) ON default.session_events                                                                                                                                                             │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') SETTINGS allow_experimental_parallel_reading_from_replicas = 2 from stage FetchColumns to stage WithMergeableState only analyze │
│ Query SELECT __table1.clientId AS clientId, __table1.sessionId AS sessionId, __table1.pageId AS pageId, __table1.timestamp AS timestamp, __table1.type AS type FROM default.session_events AS __table1 WHERE __table1.type = 'type2' LIMIT _CAST(10, 'UInt64') SETTINGS allow_experimental_parallel_reading_from_replicas = 2 from stage WithMergeableState to stage Complete │
│ The number of replicas requested (100) is bigger than the real number available in the cluster (6). Will use the latter number to execute the query.                                                                                                       │
│ Initial request from replica 4: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 4 replica
                                                                                                   │
│ Reading state is fully initialized: part all_0_2_1 with ranges [(0, 182)] in replicas [4]; part all_3_3_0 with ranges [(0, 62)] in replicas [4]                                                                                                            │
│ Sent initial requests: 1 Replicas count: 6                                                                                                                                                                                                                 │
│ Initial request from replica 2: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 2 replica
                                                                                                   │
│ Sent initial requests: 2 Replicas count: 6                                                                                                                                                                                                                 │
│ Handling request from replica 4, minimal marks size is 240                                                                                                                                                                                                 │
│ Going to respond to replica 4 with 1 parts: [part all_0_2_1 with ranges [(128, 182)]]. Finish: false; mine_marks=0, stolen_by_hash=54, stolen_rest=0                                                                                                       │
│ Initial request from replica 1: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 1 replica
                                                                                                   │
│ Sent initial requests: 3 Replicas count: 6                                                                                                                                                                                                                 │
│ Handling request from replica 4, minimal marks size is 240                                                                                                                                                                                                 │
│ Going to respond to replica 4 with 2 parts: [part all_0_2_1 with ranges [(0, 128)], part all_3_3_0 with ranges [(0, 62)]]. Finish: false; mine_marks=0, stolen_by_hash=0, stolen_rest=190                                                                  │
│ Initial request from replica 0: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 0 replica
                                                                                                   │
│ Sent initial requests: 4 Replicas count: 6                                                                                                                                                                                                                 │
│ Initial request from replica 5: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 5 replica
                                                                                                   │
│ Sent initial requests: 5 Replicas count: 6                                                                                                                                                                                                                 │
│ Handling request from replica 2, minimal marks size is 240                                                                                                                                                                                                 │
│ Going to respond to replica 2 with 0 parts: []. Finish: true; mine_marks=0, stolen_by_hash=0, stolen_rest=0                                                                                                                                                │
│ Initial request from replica 3: 2 parts: [part all_0_2_1 with ranges [(0, 182)], part all_3_3_0 with ranges [(0, 62)]]----------
Received from 3 replica