As EXPLAIN shows the execution plan of a query or job before execution, EXPLAIN ANALYZE analyzes a running stream job, including table, materialized view, sink, or index, and collects runtime statistics to help identify performance bottlenecks.

EXPLAIN ANALYZE is enabled by default. To disable it, set enable_explain_analyze_stats = false under [streaming.developer].

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Syntax

EXPLAIN ANALYZE (duration_secs <secs>) [TABLE <name> | MATERIALIZED VIEW <name> | SINK <name> | INDEX <name> | ID <job_id>]

duration_secs specifies the profiling duration in seconds.

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Metrics

When you run EXPLAIN ANALYZE, it returns a table showing runtime statistics for each operator involved in the execution.

Field nameDescription
identityThe name and hierarchical structure of the operator (e.g., StreamHashJoin, MergeExecutor.
actor_idsThe IDs of concurrent actors running this operator.
output_rpsThe number of records output per second (records per second).
avg_output_pending_ratioThe average ratio of pending outputs in the buffer, indicating how quickly downstream operators are consuming data.

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Example

CREATE TABLE t(v1 int);

CREATE MATERIALIZED VIEW m1 as 
  select * from 
    t x join t y using(v1)
      join t z using(v1) 
        join t c using(v1);

EXPLAIN ANALYZE MATERIALIZED VIEW m1;

Sample output:

                     identity                   |  actor_ids  | output_rps | avg_output_pending_ratio
------------------------------------------------+-------------+------------+--------------------------
 StreamMaterialize                              | 12,11,10,9  | 41589.1    | 0.00005
 └─ MergeExecutor                               | 12,11,10,9  | 41589.1    | 0.8149749999999999
    └─ Dispatcher                               |             | 0          | NaN
       └─ StreamHashJoin                        | 16,15,14,13 | 41560.1    | 0.859225
          ├─ StreamHashJoin                     | 16,15,14,13 | 152.6      | 0.93265
          │  ├─ MergeExecutor                   | 16,15,14,13 | 25.6       | 1.6336749999999998
          │  │  └─ Dispatcher                   |             | 0          | NaN
          │  │     └─ StreamFilter              | 20,19,18,17 | 0          | 0
          │  │        └─ StreamTableScan        | 20,19,18,17 | 0          | 0
          │  │           ├─ BatchPlanNode       | 20,19,18,17 | 0          | 0
          │  │           └─ Upstream            | 20,19,18,17 | 0          | 0
          │  └─ MergeExecutor                   | 16,15,14,13 | 0          | 0
          │     └─ Dispatcher                   |             | 0          | NaN
          │        └─ StreamFilter              | 28,27,26,25 | 0          | 0
          │           └─ StreamTableScan        | 28,27,26,25 | 0          | 0
          │              ├─ BatchPlanNode       | 28,27,26,25 | 0          | 0
          │              └─ Upstream            | 28,27,26,25 | 0          | 0
          └─ MergeExecutor                      | 16,15,14,13 | 51.2       | 0.71425
             └─ Dispatcher                      |             | 0          | NaN
                └─ StreamHashJoin               | 24,23,22,21 | 51.2       | 0.711325
                   ├─ MergeExecutor             | 24,23,22,21 | 0          | 0
                   │  └─ Dispatcher             |             | 0          | NaN
                   │     └─ StreamFilter        | 36,35,34,33 | 0          | 0
                   │        └─ StreamTableScan  | 36,35,34,33 | 0          | 0
                   │           ├─ BatchPlanNode | 36,35,34,33 | 0          | 0
                   │           └─ Upstream      | 36,35,34,33 | 0          | 0
                   └─ MergeExecutor             | 24,23,22,21 | 0          | 0
                      └─ Dispatcher             |             | 0          | NaN
                         └─ StreamFilter        | 32,31,30,29 | 0          | 0
                            └─ StreamTableScan  | 32,31,30,29 | 0          | 0
                               ├─ BatchPlanNode | 32,31,30,29 | 0          | 0
                               └─ Upstream      | 32,31,30,29 | 0          | 0
(32 rows)
  • To check the execution plan for a new statement before it runs, see EXPLAIN.
  • To check the execution fragments of an existing streaming job, see DESCRIBE FRAGMENTS.