小编Jan*_*ins的帖子

在对分区进行连接时与在整个表上进行连接时，以下连接具有非常不同的行估计：

CREATE TABLE m_data.ga_session (
  session_id         BIGINT                   NOT NULL,
  visitor_id         BIGINT                   NOT NULL,
  transaction_id     TEXT,

  timestamp          TIMESTAMP WITH TIME ZONE NOT NULL,
  day_id             INTEGER                  NOT NULL,
  [...]

  device_category    TEXT                     NOT NULL,
  [...]
  operating_system   TEXT

);

对于所有分区：

CREATE TABLE IF NOT EXISTS m_data.ga_session_20170127 ( CHECK (day_id = 20170127) ) INHERITS (m_data.ga_session);
-- the identifier are theoretically invalid, but they get truncated to 63 chars and nevertheless work
CREATE INDEX IF NOT EXISTS "ga_session__m_tmp.normalize_device_category(ga_session.device_category)" on m_data.ga_session_20170127 USING btree (m_tmp.normalize_device_category(device_category)) ;
CREATE INDEX …