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+====== Хелперы работы с clickhouse ======
+<code>
+SELECT partition, name, table FROM system.parts WHERE active
+</code>
+ss
+<code>
+SELECT * FROM system.parts WHERE active limit 1
+</code>
+ss
+<code>
+SELECT
+    name,
+    type,
+    formatReadableSize(data_compressed_bytes) AS compressed,
+    formatReadableSize(data_uncompressed_bytes) AS uncompressed,
+    data_uncompressed_bytes / data_compressed_bytes AS ratio,
+    compression_codec
+FROM system.columns
+WHERE (database = 'traffic') AND (table = 'raw')
+ORDER BY data_compressed_bytes DESC
+</code>
+===== Изменение алгоритма компресии для колонки =====
+<code>
+ALTER TABLE <database>.<table> MODIFY COLUMN <column> CODEC(Delta(4), ZSTD(10))
+</code>
+Changes are applied lazily: only for new data and while merging. A trick to rewrite column data on disk:
+<code>
+ALTER TABLE <database>.<table> UPDATE <column> = <column> WHERE 1
+</code>
+Процедура выполняется в фоне, чтобы проверить статус:
+<code>
+select * from system.mutations
+</code>

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