Understanding Query iterator

posted Apr 28, 2017, 10:08 AM by Sachchida Ojha
The gpperfmon database iterators_* tables store information about query plan iterators and their metrics. A query iterator refers to a node or operation in a query plan. Here are the list of all possible iterators in a query on Greenplum Database instance. The iterator tables include the metric name, the column in the iterators_* table in the gpperfmon database where the metric appears, how the metric is measured (unit), and a description of the metric. The following iterators are listed:

  1. Append
  2. Append-only Scan
  3. Append-only Columnar Scan
  4. Aggregate
  5. BitmapAnd
  6. BitmapOr
  7. Bitmap Append-Only Scan
  8. Bitmap Heap Scan
  9. Bitmap Index Scan
  10. Broadcast Motion
  11. Explicit Redistribute Motion
  12. External Scan
  13. Function Scan
  14. Gather Motion
  15. GroupAggregate
  16. Hash Join
  17.  HashAggregate
  18.  Index Scan
  19.  Limit
  20.  Materialize
  21.  Merge Join
  22.  Nested Loop
  23.  Redistribute Motion
  24.  Result
  25.  Repeat
  26.  Seq Scan
  27.  SetOp
  28.  Shared Scan
  29.  Sort
  30.  Subquery Scan
  31.  Tid Scan
  32.  Unique
  33.  Values Scan
  34.  Window