iterators_*_rollup

The iterators_*_rollup set of views aggregate the metrics stored in the iterators_* tables. A query iterator refers to a node or operation in a query plan. For example, a sequential scan operation may be one type of iterator in a particular query plan. For each iterator in a query plan, the iterators_* tables store the metrics collected from each segment instance. The iterators_*_rollup views summarize the query iterator metrics across all segments in the system.

The tmid, ssid and ccnt columns are the composite key that uniquely identifies a particular query.

There are three iterators rollup views, all having the same columns:

  • The iterators_now_rollup view shows iterator data from the interators_now table aggregated across all segments in the system.
  • The iterators_tail_rollup view shows iterator data from the interators_tail table aggregated across all segments in the system.
  • The iterators_history_rollup shows iterator data from the interators_history table aggregated across all segments in the system.

See also the iterators_* tables for more information about the query plan iterator types and the metrics collected for each iterator.

Column Type Description
sample_time timestamp The ctime from the associated iterators_* table.
tmid int A time identifier for a particular query. All iterator records associated with the query will have the same tmid.
ssid int The session id as shown by the gp_session_id parameter. All iterator records associated with the query will have the same ssid.
ccnt int The command number within this session as shown by gp_command_count parameter. All iterator records associated with the query will have the same ccnt.
nid int

The ID of this query plan node from the slice plan.

pnid int The pnid (slice plan parent node ID) from the associated iterators_* table.
ntype text

The ntype (node/iterator type) from the associated iterators_* table.

nstatus text The accumulated status of this iterator. Possible values are: Initialize, Executing, or Finished.
tstart timestamp The average start time for this iterator.
tduration numeric The average execution time for this iterator.
pmemsize numeric The average work memory allocated by the Greenplum planner to this iterator’s query processes.
pmemmax numeric The average of the maximum planner work memory used by this iterator’s query processes.
memsize numeric The average OS memory allocated to this iterator’s processes.
memresid numeric The average resident memory allocated to this iterator’s processes (as opposed to shared memory).
memshare numeric The average shared memory allocated to this iterator’s processes.
cpu_elapsed numeric Sum of the CPU usage of all segment processes executing this iterator.
cpu_currpct double precision

The current average percentage of CPU utilization used by this iterator’s processes. This value is always zero for historical (completed) iterators.

rows_out numeric The total number of actual rows output for this iterator on all segments.
rows_out_est numeric The total number of output rows for all segments as estimated by the query planner.
skew_cpu numeric Coefficient of variation for cpu_elapsed of iterators across all segments for this query, multiplied by 100. For example, a value of .95 is rendered as 95.
skew_rows numeric Coefficient of variation for rows_out of iterators across all segments for this query, multiplied by 100. For example, a value of .95 is rendered as 95.
m0 text The name (m0_name), unit of measure (m0_unit), average actual value (m0_val), and average estimated value (m0_est) for this iterator metric across all segments. The m0 metric is always rows for all iterator types.
m1 text The name (m1_name), unit of measure (m1_unit), average actual value (m1_val), and average estimated value (m1_est) for this iterator metric across all segments.
m2 text The name (m2_name), unit of measure (m2_unit), average actual value (m2_val), and average estimated value (m2_est) for this iterator metric across all segments.
m3 text The name (m3_name), unit of measure (m3_unit), average actual value (m3_val), and average estimated value (m3_est) for this iterator metric across all segments.
m4 text The name (m4_name), unit of measure (m4_unit), average actual value (m4_val), and average estimated value (m4_est) for this iterator metric across all segments.
m5 text The name (m5_name), unit of measure (m5_unit), average actual value (m5_val), and average estimated value (m5_est) for this iterator metric across all segments.
m6 text The name (m6_name), unit of measure (m6_unit), average actual value (m6_val), and average estimated value (m6_est) for this iterator metric across all segments.
m7 text The name (m7_name), unit of measure (m7_unit), average actual value (m7_val), and average estimated value (m7_est) for this iterator metric across all segments.
m8 text The name (m8_name), unit of measure (m8_unit), average actual value (m8_val), and average estimated value (m8_est) for this iterator metric across all segments.
m9 text The name (m9_name), unit of measure (m9_unit), average actual value (m9_val), and average estimated value (m9_est) for this iterator metric across all segments.
m10 - m5 text Metrics m10 through m15 are not currently used by any iterator types.
t0 text The name of the relation (t0_val) being scanned by this iterator. This metric is collected only for iterators that perform scan operations such as a sequential scan or function scan.