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 theinterators_now
table aggregated across all segments in the system. - The
iterators_tail_rollup
view shows iterator data from theinterators_tail
table aggregated across all segments in the system. - The
iterators_history_rollup
shows iterator data from theinterators_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 |
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. |