Understanding Query iterator

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