ClickHouse/docs/en/operations/system-tables/data_skipping_indices.md

slug
/en/operations/system-tables/data_skipping_indices

data_skipping_indices

Contains information about existing data skipping indices in all the tables.

Columns:

• database (String) — Database name.
• table (String) — Table name.
• name (String) — Index name.
• type (String) — Index type.
• type_full (String) — Index type expression from create statement.
• expr (String) — Expression for the index calculation.
• granularity (UInt64) — The number of granules in the block.
• data_compressed_bytes (UInt64) — The size of compressed data, in bytes.
• data_uncompressed_bytes (UInt64) — The size of decompressed data, in bytes.
• marks_bytes (UInt64) — The size of marks, in bytes.

Example

SELECT * FROM system.data_skipping_indices LIMIT 2 FORMAT Vertical;

Row 1:
──────
database:    default
table:       user_actions
name:        clicks_idx
type:        minmax
type_full:   minmax
expr:        clicks
granularity: 1
data_compressed_bytes:   58
data_uncompressed_bytes: 6
marks:                   48

Row 2:
──────
database:    default
table:       users
name:        contacts_null_idx
type:        minmax
type_full:   minmax
expr:        assumeNotNull(contacts_null)
granularity: 1
data_compressed_bytes:   58
data_uncompressed_bytes: 6
marks:                   48