Export Performance

LakeXpress auto-detects the best export method per table. Override when needed using CLI flags or the partition_columns table in the LakeXpress DB.

Export Methods

Without Key Column

Method	Database	Description
None	All	Sequential export (no parallelism)
Ctid	PostgreSQL	Tuple ID-based parallel export
Rowid	Oracle	Row ID-based parallel export
Physloc	SQL Server	Physical location-based parallel export

With Key Column

Method	Description	Key Column
Random	Distributes using column values	Integer or bigint
DataDriven	Splits on distinct values	Column with distinct values (e.g., year, region)
RangeId	Range partitioning via min/max	Numeric or date column
Ntile	Even distribution	Numeric column
Timepartition	Partitions by date/time column into Hive-style paths	Date/datetime column: (col,year,month)

Timepartition

Splits data into time-based chunks where each parallel thread handles a specific time period. Works with any source database -- ideal for time-series data and large historical tables.

Key column format -- a parenthesized list of a date column followed by granularity levels:

Format	Output paths
(col, year)	year=YYYY/
(col, year, month)	year=YYYY/month=MM/
(col, year, month, day)	year=YYYY/month=MM/day=DD/
(col, year, week)	year=YYYY/week=WW/

Exported files follow Hive-style partitioned paths, e.g. year=2008/month=01/CARRIER_CLAIMS.parquet.

Tuning Parameters

Parameter	Default	Description
--n_jobs	1	Tables exported simultaneously
--fastbcp_p	1	Parallel threads per large table
--large_table_threshold	100000	Row count below which tables export sequentially

Both --n_jobs and --fastbcp_p default to 1 (sequential) — increase them explicitly to enable parallelism. --fastbcp_p only takes effect when its value is greater than 1; tables below --large_table_threshold always use the None (sequential) method regardless of --fastbcp_p.

Parallel degree guidelines (--fastbcp_p):

• < 100K rows: 1 (default; below large_table_threshold, parallel export is skipped regardless of --fastbcp_p)
• 100K-10M rows: 2-4
• 10M-100M rows: 4-8
• > 100M rows: 8-16

Per-Table CLI Override

--fastbcp_table_config "[schema.]table:method:key_column:parallel_degree"

The schema prefix is optional. When omitted, the config applies to all schemas containing that table (a warning is logged). Multiple tables separated by semicolons. Empty fields use defaults.

# Schema-qualified (targets specific schema)
--fastbcp_table_config "dbo.lineitem:DataDriven:YEAR(l_shipdate):8;dbo.orders:Ctid::4"

# Without schema (applies to all schemas, with warning)
--fastbcp_table_config "lineitem:DataDriven:YEAR(l_shipdate):8;orders:Ctid::4"

# Timepartition -- key column uses parenthesized format
--fastbcp_table_config "CARRIER_CLAIMS:Timepartition:(CLM_FROM_DT,year,month):4"

Per-Table Database Override

Insert into the partition_columns table for persistent configuration:

INSERT INTO partition_columns (
    source_db_type, source_database, source_schema, source_table,
    fastbcp_method, fastbcp_parallel_degree, fastbcp_distribution_key
) VALUES (
    'postgres', 'analytics', 'public', 'events',
    'Ctid', 4, NULL
);

Database configuration takes priority over CLI configuration, which takes priority over auto-detection.

Monitoring

The real table is export_jobs (there is no plain jobs table), with columns job_status, started_at/completed_at, and num_rows_exported:

SELECT source_table, job_status, started_at, completed_at, num_rows_exported
FROM export_jobs
WHERE run_id = 'your-run-id'
ORDER BY started_at DESC;