配置

By default, the Table & SQL API is preconfigured for producing accurate results with acceptable performance.

Depending on the requirements of a table program, it might be necessary to adjust certain parameters for optimization. For example, unbounded streaming programs may need to ensure that the required state size is capped (see streaming concepts).

Overview

In every table environment, the TableConfig offers options for configuring the current session.

For common or important configuration options, the TableConfig provides getters and setters methods with detailed inline documentation.

For more advanced configuration, users can directly access the underlying key-value map. The following sections list all available options that can be used to adjust Flink Table & SQL API programs.

Attention Because options are read at different point in time when performing operations, it is recommended to set configuration options early after instantiating a table environment.

// instantiate table environment
TableEnvironment tEnv = ...

tEnv.getConfig()        // access high-level configuration
  .getConfiguration()   // set low-level key-value options
  .setString("table.exec.mini-batch.enabled", "true")
  .setString("table.exec.mini-batch.allow-latency", "5 s")
  .setString("table.exec.mini-batch.size", "5000");
// instantiate table environment
val tEnv: TableEnvironment = ...

tEnv.getConfig         // access high-level configuration
  .getConfiguration    // set low-level key-value options
  .setString("table.exec.mini-batch.enabled", "true")
  .setString("table.exec.mini-batch.allow-latency", "5 s")
  .setString("table.exec.mini-batch.size", "5000")
# instantiate table environment
t_env = ...

t_env.get_config()        # access high-level configuration
  .get_configuration()    # set low-level key-value options
  .set_string("table.exec.mini-batch.enabled", "true")
  .set_string("table.exec.mini-batch.allow-latency", "5 s")
  .set_string("table.exec.mini-batch.size", "5000");

Attention Currently, key-value options are only supported for the Blink planner.

Execution Options

The following options can be used to tune the performance of the query execution.

Key Default Description
table.exec.async-lookup.buffer-capacity

Batch Streaming
100 The max number of async i/o operation that the async lookup join can trigger.
table.exec.async-lookup.timeout

Batch Streaming
"3 min" The async timeout for the asynchronous operation to complete.
table.exec.disabled-operators

Batch
(none) Mainly for testing. A comma-separated list of operator names, each name represents a kind of disabled operator. Operators that can be disabled include "NestedLoopJoin", "ShuffleHashJoin", "BroadcastHashJoin", "SortMergeJoin", "HashAgg", "SortAgg". By default no operator is disabled.
table.exec.mini-batch.allow-latency

Streaming
"-1 ms" The maximum latency can be used for MiniBatch to buffer input records. MiniBatch is an optimization to buffer input records to reduce state access. MiniBatch is triggered with the allowed latency interval and when the maximum number of buffered records reached. NOTE: If table.exec.mini-batch.enabled is set true, its value must be greater than zero.
table.exec.mini-batch.enabled

Streaming
false Specifies whether to enable MiniBatch optimization. MiniBatch is an optimization to buffer input records to reduce state access. This is disabled by default. To enable this, users should set this config to true. NOTE: If mini-batch is enabled, 'table.exec.mini-batch.allow-latency' and 'table.exec.mini-batch.size' must be set.
table.exec.mini-batch.size

Streaming
-1 The maximum number of input records can be buffered for MiniBatch. MiniBatch is an optimization to buffer input records to reduce state access. MiniBatch is triggered with the allowed latency interval and when the maximum number of buffered records reached. NOTE: MiniBatch only works for non-windowed aggregations currently. If table.exec.mini-batch.enabled is set true, its value must be positive.
table.exec.resource.default-parallelism

Batch Streaming
-1 Sets default parallelism for all operators (such as aggregate, join, filter) to run with parallel instances. This config has a higher priority than parallelism of StreamExecutionEnvironment (actually, this config overrides the parallelism of StreamExecutionEnvironment). A value of -1 indicates that no default parallelism is set, then it will fallback to use the parallelism of StreamExecutionEnvironment.
table.exec.resource.external-buffer-memory

Batch
"10 mb" Sets the external buffer memory size that is used in sort merge join and nested join and over window.
table.exec.resource.hash-agg.memory

Batch
"128 mb" Sets the managed memory size of hash aggregate operator.
table.exec.resource.hash-join.memory

Batch
"128 mb" Sets the managed memory for hash join operator. It defines the lower limit.
table.exec.resource.sort.memory

Batch
"128 mb" Sets the managed buffer memory size for sort operator.
table.exec.shuffle-mode

Batch
"batch" Sets exec shuffle mode. Only batch or pipeline can be set. batch: the job will run stage by stage. pipeline: the job will run in streaming mode, but it may cause resource deadlock that receiver waits for resource to start when the sender holds resource to wait to send data to the receiver.
table.exec.sort.async-merge-enabled

Batch
true Whether to asynchronously merge sorted spill files.
table.exec.sort.default-limit

Batch
-1 Default limit when user don't set a limit after order by. -1 indicates that this configuration is ignored.
table.exec.sort.max-num-file-handles

Batch
128 The maximal fan-in for external merge sort. It limits the number of file handles per operator. If it is too small, may cause intermediate merging. But if it is too large, it will cause too many files opened at the same time, consume memory and lead to random reading.
table.exec.source.idle-timeout

Streaming
"-1 ms" When a source do not receive any elements for the timeout time, it will be marked as temporarily idle. This allows downstream tasks to advance their watermarks without the need to wait for watermarks from this source while it is idle.
table.exec.spill-compression.block-size

Batch
"64 kb" The memory size used to do compress when spilling data. The larger the memory, the higher the compression ratio, but more memory resource will be consumed by the job.
table.exec.spill-compression.enabled

Batch
true Whether to compress spilled data. Currently we only support compress spilled data for sort and hash-agg and hash-join operators.
table.exec.window-agg.buffer-size-limit

Batch
100000 Sets the window elements buffer size limit used in group window agg operator.

Optimizer Options

The following options can be used to adjust the behavior of the query optimizer to get a better execution plan.

Key Default Description
table.optimizer.agg-phase-strategy

Batch Streaming
"AUTO" Strategy for aggregate phase. Only AUTO, TWO_PHASE or ONE_PHASE can be set. AUTO: No special enforcer for aggregate stage. Whether to choose two stage aggregate or one stage aggregate depends on cost. TWO_PHASE: Enforce to use two stage aggregate which has localAggregate and globalAggregate. Note that if aggregate call does not support optimize into two phase, we will still use one stage aggregate. ONE_PHASE: Enforce to use one stage aggregate which only has CompleteGlobalAggregate.
table.optimizer.distinct-agg.split.bucket-num

Streaming
1024 Configure the number of buckets when splitting distinct aggregation. The number is used in the first level aggregation to calculate a bucket key 'hash_code(distinct_key) % BUCKET_NUM' which is used as an additional group key after splitting.
table.optimizer.distinct-agg.split.enabled

Streaming
false Tells the optimizer whether to split distinct aggregation (e.g. COUNT(DISTINCT col), SUM(DISTINCT col)) into two level. The first aggregation is shuffled by an additional key which is calculated using the hashcode of distinct_key and number of buckets. This optimization is very useful when there is data skew in distinct aggregation and gives the ability to scale-up the job. Default is false.
table.optimizer.join-reorder-enabled

Batch Streaming
false Enables join reorder in optimizer. Default is disabled.
table.optimizer.join.broadcast-threshold

Batch
1048576 Configures the maximum size in bytes for a table that will be broadcast to all worker nodes when performing a join. By setting this value to -1 to disable broadcasting.
table.optimizer.reuse-source-enabled

Batch Streaming
true When it is true, the optimizer will try to find out duplicated table sources and reuse them. This works only when table.optimizer.reuse-sub-plan-enabled is true.
table.optimizer.reuse-sub-plan-enabled

Batch Streaming
true When it is true, the optimizer will try to find out duplicated sub-plans and reuse them.
table.optimizer.source.predicate-pushdown-enabled

Batch Streaming
true When it is true, the optimizer will push down predicates into the FilterableTableSource. Default value is true.