--- metadata: - name: generator content: Diplodoc Platform v5.50.6 alternate: - https://ytsaurus.tech/docs/en/user-guide/storage/examples.md - https://ytsaurus.tech/docs/ru/user-guide/storage/examples.md --- > **Documentation Index:** Fetch the complete configuration index at https://ytsaurus.tech/docs/en/llms.txt # Examples of Cypress object processing This section provides examples of Cypress object processing. ## Static tables { #static_tables } ### Creating { #create_table } Use the `create` command to create a table. ```bash yt create table //home/dev/test_table 1282c-1ed72c-3fe0191-443cf2ee ``` ### Deleting { #remove_table } Use the `remove` command to delete a table. ```bash yt remove //home/dev/test_table ``` ### Reading { #read_table } To read an existing table named ``, use the `read-table` command. ```bash yt read-table [--format FORMAT] [--table-reader TABLE_READER]
``` The `--format` option defines the output data format. The supported formats are `json`, `yson`, `dsv`, and `schemaful_dsv`. For more information, see [Formats](https://ytsaurus.tech/docs/en/user-guide/storage/formats.md). ```bash yt read-table --format dsv //home/dev/test_table day=monday time=10 day=wednesday time=20 day=friday time=30 ``` The `--table-reader` option modifies the table read settings. #### Sampling { #sampling_rate } The `sampling_rate` attribute sets the percentage of data that must be read from an input table. ```bash yt read-table --format dsv --table-reader '{"sampling_rate"=0.3}' //home/dev/test_table day=monday time=10 day=friday time=30 ``` In this example, `read-table` will return 30% of all the rows in the input table. The `sampling_seed` controls a random number generator that selects the rows. It guarantees the same output for the same `sampling_speed` and collection of input chunks. If unspecified, the `sampling_seed` attribute will be random. ```bash yt read-table --format dsv --table-reader '{"sampling_seed"=42;"sampling_rate"=0.3}' //home/dev/test_table ``` To place sampling output in a different table, please run `map`: ```bash yt map cat --src //home/dev/input --dst //home/dev/output --spec '{job_io = {table_reader = {sampling_rate = 0.001}}}' --format yson ``` {% note info "Note" %} The specified `sampling_rate` attribute notwithstanding, sampling reads all data from disk. {% endnote %} ### Overwriting { #write_table } The `write-table` command overwrites an existing table called `
` with the data transmitted. ```bash yt write-table [--format FORMAT] [--table-writer TABLE_WRITER]
``` The `--format` option defines the input data format. The supported formats are `json`, `yson`, `dsv`, and `schemaful_dsv`. For more information, see [Formats](https://ytsaurus.tech/docs/en/user-guide/storage/formats.md). ```bash yt write-table --format dsv //home/dev/test_table time=10 day=monday time=20 day=wednesday time=30 day=friday ^D ``` To add records to a table, use the `` option before the table path. ```bash cat test_table.json {"time":"10","day":"monday"} {"time":"20","day":"wednesday"} {"time":"30","day":"friday"} cat test_table.json | yt write-table --format json ""//home/dev/test_table ``` The `--table-writer` option modifies the table write settings: * [Limit on table row size.](#max_row_weight) * [Chunk size.](#desired_chunk_size) * [Replication factor.](#replication_factor) ##### Limit on table row size { #max_row_weight } When writing table data, the YTsaurus system checks its size. A write will return an error if the size is greater than the maximum legal value. By default, maximum row size is 16 MB. To modify this value, use the `--table-writer` option's `max_row_weight` parameter. Enter a value in bytes. ```bash cat test_table.json | yt write-table --format json --table-writer {"max_row_weight"=33554432} //home/dev/test_table ``` {% note info "Note" %} `max_row_weight` cannot be greater than 128 MB. {% endnote %} #### Chunk size { #desired_chunk_size } The `desired_chunk_size` defines chunk size in bytes. ```bash cat test_table.json | yt write-table --format json --table-writer {"desired_chunk_size"=1024} //home/dev/test_table ``` #### Replication factor { #replication_factor } You can control the replication factor for new table chunks through the `min_upload_replication_factor` and the `upload_replication_factor` attributes. `upload_replication_factor` sets the number of synchronous replicas created when writing new data to a table. `min_upload_replication_factor` sets the minimum number of successfully written chunks. Both attributes have a default value of 2 and a maximum value of 10. ```bash cat test_table.json | yt write-table --format json --table-writer '{"upload_replication_factor"=5;"min_upload_replication_factor"=3}' //home/dev/test_table ``` To increase the number of replicas of an existing table, use one of the methods below: - Start a Merge operation: ```bash yt merge --mode auto --spec '{"force_transform"=true; "job_io"={"table_writer"={"upload_replication_factor"=5}}}' --src <> --dst <> ``` - Increase the table's `replication_factor` attribute. This will perform the conversion in the background at a later point in time. New records added to the table will have a replication factor set by the `upload_replication_factor` attribute. Subsequently, a background process will asynchronously replicate chunks to achieve the replication factor defined for the specific table. ```bash yt set //home/dev/test_table/@replication_factor 5 ``` ### Medium { #medium } To move a table to a different medium, change the value of the `primary_medium` attribute. New data written to the table will be delivered directly to the new medium while old data will move in the background. To force-move data to a new medium, start a Merge: ```bash yt set //home/dev/test_table/@primary_medium ssd_blobs yt merge --mode auto --spec '{"force_transform"=true;}' --src //home/dev/test_table --dst //home/dev/test_table ``` To check whether a table's medium has changed, run the command below: ```bash $ yt get //home/dev/test_table/@chunk_media_statistics { "ssd_blobs" = { "chunk_count" = 2126; "uncompressed_data_size" = 9667220402266; "compressed_data_size" = 4954465956017; "data_weight" = 10764306825793; "max_block_size" = 6584787; }; } ``` The amount is shown in bytes.