Scylla SStable¶

Syntax¶

The command syntax is as follows:

scylla sstable <operation> <path to SStable>

You can specify more than one SStable.

Schema¶

All operations need a schema to interpret the SStables with. Currently, there are two ways to obtain the schema:

• --schema-file FILENAME - Read the schema definition from a file.

• --system-schema KEYSPACE.TABLE - Use the known definition of built-in tables (only works for system tables).

By default, the tool uses the first method: --schema-file schema.cql; i.e. it assumes there is a schema file named schema.cql in the working directory. If this fails, it will exit with an error.

The schema file should contain all definitions needed to interpret data belonging to the table.

Example schema.cql:

CREATE KEYSPACE ks WITH replication = {'class': 'NetworkTopologyStrategy', 'mydc1': 1, 'mydc2': 4};

CREATE TYPE ks.mytype (
    f1 int,
    f2 text
);

CREATE TABLE ks.cf (
    pk int,
    ck text,
    v1 int,
    v2 mytype,
    PRIMARY KEY (pk, ck)
);

Note:

• In addition to the table itself, the definition also has to includes any user defined types the table uses.

• The keyspace definition is optional, if missing one will be auto-generated.

• The schema file doesn’t have to be called schema.cql, this is just the default name. Any file name is supported (with any extension).

INSERT INTO system_schema.dropped_columns (
    keyspace_name,
    table_name,
    column_name,
    dropped_time,
    type
) VALUES (
    'ks',
    'cf',
    'v1',
    1631011979170675,
    'int'
);

CREATE TABLE ks.cf (pk int PRIMARY KEY, v2 int);

scylla sstable dump-data --system-schema system.local ./path/to/md-123456-big-Data.db

Supported Operations¶

The dump-* operations output JSON. For dump-data, you can specify another output format.

• dump-data - Dumps the content of the SStable. You can use it with additional parameters:

  • --merge - Allows you to process multiple SStables as a unified stream (if not specified, multiple SStables are processed one by one).

  • --partition={{<partition key>}} or partitions-file={{<partition key>}} - Allows you to narrow down the scope of the operation to specified partitions. To specify the partition(s) you want to be processed, provide partition keys in the hexdump format used by ScyllaDB (the hex representation of the raw buffer).

  • --output-format=<format> - Allows you to specify the output format: json or text.

• dump-index - Dumps the content of the SStable index.

• dump-compression-info - Dumps the SStable compression information, including compression parameters and mappings between compressed and uncompressed data.

• dump-summary - Dumps the summary of the SStable index.

• dump-statistics - Dumps the statistics of the SStable, including metadata about the data component.

• dump-scylla-metadata - Dumps the SStable’s scylla-specific metadata.

• writetime-histogram - Generates a histogram of all the timestamps in the SStable. You can use it with a parameter:

  • --bucket=<unit> - Allows you to specify the unit of time to be used as bucket (years, months, weeks, days, or hours).

• validate - Validates the content of the SStable with the mutation fragment stream validator.

• validate-checksums - Validates SStable checksums (full checksum and per-chunk checksum) against the SStable data.

• decompress - Decompresses the data component of the SStable (the *-Data.db file) if compressed. The decompressed data is written to a *-Data.decompressed file.

Examples¶

Dumping the content of the SStable:

scylla sstable dump-data /path/to/md-123456-big-Data.db

Dumping the content of two SStables as a unified stream:

scylla sstable dump-data --merge /path/to/md-123456-big-Data.db /path/to/md-123457-big-Data.db

Validating the specified SStables:

scylla sstable validate /path/to/md-123456-big-Data.db /path/to/md-123457-big-Data.db