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Communication Directives

The communication directives are special instructions in conditional queries that modify how the query engine handles data transfer during querying.

The following directives are supported:

DirectiveReductStore VersionDescription
Communication
#batch_sizev1.17Maximum size of a batch of records returned by the query.
#batch_recordsv1.17Maximum number of records in a batch returned by the query.
#batch_metadata_sizev1.17Maximum size of metadata in a batch returned by the query.
#batch_timeoutv1.17Maximum time to wait before sending a batch of records.
#record_timeoutv1.17Maximum time to wait for a record to be processed before sending a batch.
#io_timeoutv1.17Maximum time to wait for I/O operations during querying. Reserved for future use.

#batch_size​

The #batch_size directive sets the maximum size (in bytes) of a batch of records returned by the query.

Syntax​

{
  "#batch_size": <expression as int | string>
}

If the expression is a string, it can include size suffixes like KB, MB, or GB (e.g. "10MB").

Behavior​

The querying stops when the batch size is reached but puts the current record in the batch, even if it exceeds the limit. It means that the actual batch size may be larger than the specified limit.

This directive overrides the server's RS_IO_BATCH_MAX_SIZE setting. See the server configuration documentation for more details.

Example​

{
  "#batch_size": "5MB"
}

#batch_records​

The #batch_records directive sets the maximum number of records in a batch returned by the query.

Syntax​

{
  "#batch_records": <expression as int>
}

Behavior​

The querying stops when the number of records in the batch reaches the specified limit.

This directive overrides the server's RS_IO_BATCH_MAX_RECORDS setting. See the server configuration documentation for more details.

Example​

{
  "#batch_records": 1000
}

#batch_metadata_size​

The #batch_metadata_size directive sets the maximum size (in bytes) of metadata in a batch returned by the query.

Syntax​

{
  "#batch_metadata_size": <expression as int | string>
}

If the expression is a string, it can include size suffixes like KB, MB, or GB (e.g. "1MB").

Behavior​

The querying stops when the metadata size in the batch reaches the specified limit but puts the current record in the batch, even if it exceeds the limit. It means that the actual metadata size may be larger than the specified limit.

This directive overrides the server's RS_IO_BATCH_MAX_METADATA_SIZE setting. See the server configuration documentation for more details.

Example​

{
  "#batch_metadata_size": "500KB"
}

#batch_timeout​

The #batch_timeout directive sets the maximum time to wait before sending a batch of records.

Syntax​

{
  "#batch_timeout": <expression as duration literal>
}

Behavior​

The querying sends the current batch when the timeout is reached, even if the batch is not full.

This directive overrides the server's RS_IO_BATCH_TIMEOUT setting. See the server configuration documentation for more details.

Example​

{
  "#batch_timeout": "200ms"
}
info

The #batch_timeout directive is ignored in replication conditional queries.

#record_timeout​

The #record_timeout directive sets the maximum time to wait for a record to be processed before sending a batch.

Syntax​

{
  "#record_timeout": <expression as duration literal>
}

Behavior​

The querying sends the current batch when the timeout is reached, even if the current record is not fully processed.

This directive overrides the server's RS_IO_BATCH_RECORD_TIMEOUT setting. See the server configuration documentation for more details.

Example​

{
  "#record_timeout": "100ms"
}
info

The #record_timeout directive is ignored in replication conditional queries.

#io_timeout​

The #io_timeout directive sets the maximum time to wait for I/O operations during querying.

Syntax​

{
  "#io_timeout": <expression as duration literal>
}

Behavior​

The querying aborts if an I/O operation takes longer than the specified timeout.

info

This directive is reserved for future use and currently has no effect.

Example​

{
  "#io_timeout": "5s"
}