Class: ClickHouse::SyncCursor

Inherits:
Object
  • Object
show all
Defined in:
lib/click_house/sync_cursor.rb

Constant Summary collapse

QUERY = 
<<~SQL
  SELECT argMax(primary_key_value, recorded_at) AS primary_key_value
  FROM sync_cursors
  WHERE table_name = {table_name:String}
  LIMIT 1
SQL
INSERT_CURSOR_QUERY = 
<<~SQL
  INSERT INTO sync_cursors
  (primary_key_value, table_name, recorded_at)
  VALUES ({primary_key_value:UInt64}, {table_name:String}, {recorded_at:DateTime64})
SQL

Class Method Summary collapse

Class Method Details

.cursor_for(identifier) ⇒ Object 



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# File 'lib/click_house/sync_cursor.rb', line 18

def self.cursor_for(identifier)
  query = ClickHouse::Client::Query.new(
    raw_query: QUERY,
    placeholders: { table_name: identifier.to_s }
  )

  # The query returns the default value (0) when no records are present.
  ClickHouse::Client.select(query, :main).first['primary_key_value']
end

.update_cursor_for(identifier, value) ⇒ Object 



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# File 'lib/click_house/sync_cursor.rb', line 28

def self.update_cursor_for(identifier, value)
  query = ClickHouse::Client::Query.new(
    raw_query: INSERT_CURSOR_QUERY,
    placeholders: {
      primary_key_value: value,
      table_name: identifier.to_s,
      recorded_at: Time.current.to_f
    }
  )

  ClickHouse::Client.execute(query, :main)
end