alamb commented on code in PR #15708: URL: https://github.com/apache/datafusion/pull/15708#discussion_r2049366426
########## docs/source/user-guide/sql/format_options.md: ########## @@ -0,0 +1,209 @@ +<!--- + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, + software distributed under the License is distributed on an + "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + KIND, either express or implied. See the License for the + specific language governing permissions and limitations + under the License. +--> + +# Format Options + +DataFusion supports customizing how data is read from or written to disk as a result of a `COPY`, `INSERT INTO`, or `CREATE EXTERNAL TABLE` statements. There are a few special options, file format (e.g., CSV or Parquet) specific options, and Parquet column-specific options. In some cases, Options can be specified in multiple ways with a set order of precedence. + +## Specifying Options and Order of Precedence + +Format-related options can be specified in three ways, in decreasing order of precedence: + +- `CREATE EXTERNAL TABLE` syntax +- `COPY` option tuples +- Session-level config defaults + +For a list of supported session-level config defaults, see [Configuration Settings](../configs). These defaults apply to all operations but have the lowest level of precedence. + +If creating an external table, table-specific format options can be specified when the table is created using the `OPTIONS` clause: + +```sql +CREATE EXTERNAL TABLE + my_table(a bigint, b bigint) + STORED AS csv + LOCATION '/test/location/my_csv_table/' + OPTIONS( + NULL_VALUE 'NAN', + 'has_header' 'true', + 'format.delimiter' ';' + ); +``` + +When running `INSERT INTO my_table ...`, the options from the `CREATE TABLE` will be respected (e.g., gzip compression, special delimiter, and header row included). Note that compression, header, and delimiter settings can also be specified within the `OPTIONS` tuple list. Dedicated syntax within the SQL statement always takes precedence over arbitrary option tuples, so if both are specified, the `OPTIONS` setting will be ignored. + +Finally, options can be passed when running a `COPY` command. + +```sql +COPY source_table + TO 'test/table_with_options' + PARTITIONED BY (column3, column4) + OPTIONS ( + format parquet, + compression snappy, + 'compression::column1' 'zstd(5)', + ) +``` + +In this example, we write the entirety of `source_table` out to a folder of Parquet files. One Parquet file will be written in parallel to the folder for each partition in the query. The next option `compression` set to `snappy` indicates that unless otherwise specified, all columns should use the snappy compression codec. The option `compression::col1` sets an override, so that the column `col1` in the Parquet file will use the ZSTD compression codec with compression level `5`. In general, Parquet options that support column-specific settings can be specified with the syntax `OPTION::COLUMN.NESTED.PATH`. + +# Available Options + +## Execution-Specific Options + +The following options are available when executing a `COPY` query. + +| Option Key | Description | Default Value | Review Comment: This largely replicates what is already in this page: https://datafusion.apache.org/user-guide/configs.html I think the idea is that the format_options page will describe options specific to formats -- I will push a small commit to fix ########## docs/source/user-guide/sql/format_options.md: ########## @@ -0,0 +1,209 @@ +<!--- + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, + software distributed under the License is distributed on an + "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + KIND, either express or implied. See the License for the + specific language governing permissions and limitations + under the License. +--> + +# Format Options + +DataFusion supports customizing how data is read from or written to disk as a result of a `COPY`, `INSERT INTO`, or `CREATE EXTERNAL TABLE` statements. There are a few special options, file format (e.g., CSV or Parquet) specific options, and Parquet column-specific options. In some cases, Options can be specified in multiple ways with a set order of precedence. + +## Specifying Options and Order of Precedence + +Format-related options can be specified in three ways, in decreasing order of precedence: + +- `CREATE EXTERNAL TABLE` syntax +- `COPY` option tuples +- Session-level config defaults + +For a list of supported session-level config defaults, see [Configuration Settings](../configs). These defaults apply to all operations but have the lowest level of precedence. + +If creating an external table, table-specific format options can be specified when the table is created using the `OPTIONS` clause: + +```sql +CREATE EXTERNAL TABLE + my_table(a bigint, b bigint) + STORED AS csv + LOCATION '/test/location/my_csv_table/' + OPTIONS( + NULL_VALUE 'NAN', + 'has_header' 'true', + 'format.delimiter' ';' + ); +``` + +When running `INSERT INTO my_table ...`, the options from the `CREATE TABLE` will be respected (e.g., gzip compression, special delimiter, and header row included). Note that compression, header, and delimiter settings can also be specified within the `OPTIONS` tuple list. Dedicated syntax within the SQL statement always takes precedence over arbitrary option tuples, so if both are specified, the `OPTIONS` setting will be ignored. + +Finally, options can be passed when running a `COPY` command. + +```sql +COPY source_table + TO 'test/table_with_options' + PARTITIONED BY (column3, column4) + OPTIONS ( + format parquet, + compression snappy, + 'compression::column1' 'zstd(5)', + ) +``` + +In this example, we write the entirety of `source_table` out to a folder of Parquet files. One Parquet file will be written in parallel to the folder for each partition in the query. The next option `compression` set to `snappy` indicates that unless otherwise specified, all columns should use the snappy compression codec. The option `compression::col1` sets an override, so that the column `col1` in the Parquet file will use the ZSTD compression codec with compression level `5`. In general, Parquet options that support column-specific settings can be specified with the syntax `OPTION::COLUMN.NESTED.PATH`. + +# Available Options + +## Execution-Specific Options + +The following options are available when executing a `COPY` query. + +| Option Key | Description | Default Value | +| ----------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ | ------------- | +| execution.batch_size | Default batch size while creating new batches. | 8192 | +| execution.coalesce_batches | Whether to coalesce small batches into larger ones between operators. | true | +| execution.collect_statistics | Should DataFusion collect statistics after listing files. | false | +| execution.target_partitions | Number of partitions for query execution. Defaults to number of CPU cores. | (num_cpus) | +| execution.time_zone | The default time zone (e.g., "+00:00"). | "+00:00" | +| execution.planning_concurrency | Fan-out during initial physical planning. Defaults to number of CPU cores. | (num_cpus) | +| execution.skip_physical_aggregate_schema_check | Skip verifying that the schema produced by planning the input of `Aggregate` matches the input plan. | false | +| execution.sort_spill_reservation_bytes | Reserved memory for each spillable sort operation (bytes). | 10485760 | +| execution.sort_in_place_threshold_bytes | Below what size should data be concatenated and sorted in a single RecordBatch (bytes). | 1048576 | +| execution.meta_fetch_concurrency | Number of files to read in parallel when inferring schema and statistics. | 32 | +| execution.minimum_parallel_output_files | Guarantees a minimum level of output files running in parallel. | 4 | +| execution.soft_max_rows_per_output_file | Target number of rows in output files when writing multiple (soft max). | 50000000 | +| execution.max_buffered_batches_per_output_file | Maximum number of RecordBatches buffered for each output file. | 2 | +| execution.listing_table_ignore_subdirectory | Should subdirectories be ignored when scanning directories for data files. | true | +| execution.enable_recursive_ctes | Should DataFusion support recursive CTEs. | true | +| execution.split_file_groups_by_statistics | Attempt to eliminate sorts by packing & sorting files with non-overlapping statistics into same file groups. | false | +| execution.keep_partition_by_columns | Should DataFusion keep the columns used for partition_by in the output RecordBatches. | false | +| execution.skip_partial_aggregation_probe_ratio_threshold | Aggregation ratio threshold for skipping partial aggregation. | 0.8 | +| execution.skip_partial_aggregation_probe_rows_threshold | Number of input rows partial aggregation partition should process before switching mode. | 100000 | +| execution.use_row_number_estimates_to_optimize_partitioning | Use row number estimates to optimize partitioning. | false | +| execution.enforce_batch_size_in_joins | Should DataFusion enforce batch size in joins. | false | + +**Usage Example:** + +```sql +COPY my_table TO '/tmp/output.csv' +OPTIONS ( + 'execution.batch_size' '4096', + 'execution.target_partitions' '8', + 'execution.keep_partition_by_columns' 'true' +); +``` + +Note: `execution.keep_partition_by_columns` flag can also be enabled through `ExecutionOptions` within `SessionConfig`. + +## JSON Format Options + +The following options are available when reading or writing JSON files. Note: If any unsupported option is specified, an error will be raised and the query will fail. + +| Option | Description | Default Value | +| ----------- | ---------------------------------------------------------------------------------------------------------------------------------- | ------------- | +| COMPRESSION | Sets the compression that should be applied to the entire JSON file. Supported values are GZIP, BZIP2, XZ, ZSTD, and UNCOMPRESSED. | UNCOMPRESSED | + +**Example:** + +```sql +CREATE EXTERNAL TABLE t(a int) +STORED AS JSON +LOCATION '/tmp/foo/' +OPTIONS('COMPRESSION' 'gzip'); +-- Inserting arow creates a new file in /tmp/foo +INSERT INTO t VALUES(1); +``` + +## CSV Format Options + +The following options are available when reading or writing CSV files. Note: If any unsupported option is specified, an error will be raised and the query will fail. + +| Option | Description | Default Value | +| -------------------- | --------------------------------------------------------------------------------------------------------------------------------- | ------------------ | +| COMPRESSION | Sets the compression that should be applied to the entire CSV file. Supported values are GZIP, BZIP2, XZ, ZSTD, and UNCOMPRESSED. | UNCOMPRESSED | +| HAS_HEADER | Sets if the CSV file should include column headers. If not set, uses session or system default. | None | +| DELIMITER | Sets the character which should be used as the column delimiter within the CSV file. | `,` (comma) | +| QUOTE | Sets the character which should be used for quoting values within the CSV file. | `"` (double quote) | +| TERMINATOR | Sets the character which should be used as the line terminator within the CSV file. | None | +| ESCAPE | Sets the character which should be used for escaping special characters within the CSV file. | None | +| DOUBLE_QUOTE | Sets if quotes within quoted fields should be escaped by doubling them (e.g., `"aaa""bbb"`). | None | +| NEWLINES_IN_VALUES | Sets if newlines in quoted values are supported. If not set, uses session or system default. | None | +| DATE_FORMAT | Sets the format that dates should be encoded in within the CSV file. | None | +| DATETIME_FORMAT | Sets the format that datetimes should be encoded in within the CSV file. | None | +| TIMESTAMP_FORMAT | Sets the format that timestamps should be encoded in within the CSV file. | None | +| TIMESTAMP_TZ_FORMAT | Sets the format that timestamps with timezone should be encoded in within the CSV file. | None | +| TIME_FORMAT | Sets the format that times should be encoded in within the CSV file. | None | +| NULL_VALUE | Sets the string which should be used to indicate null values within the CSV file. | None | +| NULL_REGEX | Sets the regex pattern to match null values when loading CSVs. | None | +| SCHEMA_INFER_MAX_REC | Sets the maximum number of records to scan to infer the schema. | None | +| COMMENT | Sets the character which should be used to indicate comment lines in the CSV file. | None | + +**Example:** + +```sql +CREATE EXTERNAL TABLE t (col1 varchar, col2 int, col3 boolean) +STORED AS CSV +LOCATION '/tmp/foo/' +OPTIONS('DELIMITER' '|', 'HAS_HEADER' 'true', 'NEWLINES_IN_VALUES' 'true'); +``` + +## Parquet Format Options Review Comment: 👍 this looks great -- This is an automated message from the Apache Git Service. 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