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See the ClickHouse guide for usage examples, table design, and setup instructions. 
import { clickhouseTarget } from '@subsquid/pipes/targets/clickhouse'

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clickhouseTarget

clickhouseTarget<T>({
  client: ClickHouseClient,
  onStart?: (ctx: { store: ClickhouseStore; logger: Logger }) => unknown | Promise<unknown>,
  onData: (ctx: { store: ClickhouseStore; data: T; ctx: Ctx }) => unknown | Promise<unknown>,
  onRollback?: (ctx: {
    type: 'offset_check' | 'blockchain_fork'
    store: ClickhouseStore
    safeCursor: BlockCursor
    /** @deprecated Use `safeCursor` instead. */
    cursor: BlockCursor
  }) => unknown | Promise<unknown>,
  settings?: Settings,
})
ParameterRequiredDescription
clientYesClient from @clickhouse/client.
onStartNoRuns once before processing starts. Use for table creation or other setup.
onDataYesCalled for each batch.
onRollbackNoCalled on startup ('offset_check') and on each fork ('blockchain_fork').
settingsNoConfiguration for the internal cursor state table. See Settings below.
Settings:
FieldDefaultDescription
databaseClient’s configured databaseClickHouse database for the state table.
table'sync'Name of the state table.
id'stream'Stream identifier within the state table.
maxRows10000Maximum rows retained per stream id in the state table.

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ClickhouseStore methods

MethodDescription
store.insert(params)Queues an insert. Non-blocking — returns a Promise but need not be awaited inside onData; inserts are flushed when the target closes.
store.query(params)Passthrough to client.query().
store.command(params)Passthrough to client.command().
store.removeAllRows({ tables, where, params? })Cancels rows matching where by re-inserting them with sign = -1. Requires CollapsingMergeTree.
store.removeAllRowsByQuery({ table, query, params? })Like removeAllRows, but uses a custom SELECT to identify the rows to cancel.
store.executeFiles(dir)Executes all .sql files found in dir.