Rajesh Balamohan created HIVE-16290:
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Summary: Stats: StatsRulesProcFactory::evaluateComparator
estimates are wrong when minValue == filterValue
Key: HIVE-16290
URL: https://issues.apache.org/jira/browse/HIVE-16290
Project: Hive
Issue Type: Bug
Components: Statistics
Reporter: Rajesh Balamohan
Priority: Minor
Issue:
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In {{StatsRulesProcFactory::evaluateCompator}}, when {{minValue}} is >=
filtered {{value}}, it should return all rows. Currently, it returns
{{numRows/3}}. This lesser number of reducers to be spun up in queries. E.g Q79
in TPC-DS.
E.g: TPC-DS store table stats:
=============================
{noformat}
hive --orcfiledump
hdfs://nn:8020/apps/hive/warehouse/tpcds_bin_partitioned_orc_1000.db/store/000000_0
Stripe Statistics:
Stripe 1:
Column 0: count: 1002 hasNull: false
Column 1: count: 1002 hasNull: false min: 1 max: 1002 sum: 502503
Column 2: count: 1002 hasNull: false min: AAAAAAAAAABAAAAA max:
AAAAAAAAPPBAAAAA sum: 16032
Column 3: count: 1002 hasNull: false min: max: 2001-03-13 sum: 9950
Column 4: count: 1002 hasNull: false min: max: 2001-03-12 sum: 5010
Column 5: count: 273 hasNull: true min: 2450820 max: 2451313 sum: 669141525
Column 6: count: 1002 hasNull: false min: max: pri sum: 3916
Column 7: count: 994 hasNull: true min: 200 max: 300 sum: 249970
Column 8: count: 996 hasNull: true min: 5002549 max: 9997773 sum: 7382689071
Column 9: count: 1002 hasNull: false min: max: 8AM-8AM sum: 7088
select compute_stats(s_employee_count, 16) from store;
{"columntype":"Long","min":200,"max":300,"countnulls":8,"numdistinctvalues":63,"ndvbitvector":"{0,
1, 2, 3, 4, 5, 11, 12}{0, 1, 2, 3, 6}{0, 1, 2, 3, 4, 5, 7, 11}{0, 1, 2, 3, 4,
5, 7}{0, 1, 2, 3, 4, 5, 6}{0, 1, 2, 3, 4, 5, 8}{0, 1, 2, 3, 4}{0, 1, 2, 3, 4,
5, 7, 9}{0, 1, 2, 3, 4}{0}{0, 1, 2, 3, 4, 5, 7}{0, 1, 2, 3, 4, 5, 6, 7}{0, 1,
2, 3, 4, 8, 9, 14}{0, 1, 2, 3, 5}{0, 1, 2, 3, 4, 5, 6, 7}{0, 1, 2, 3, 4, 5, 6,
8}"}
{noformat}
{noformat}
explain select count(s_store_sk) from store where s_number_employees > 200 and
s_number_employees < 295;
{noformat}
Above query would first apply 1002/3 = 334 for {{s_number_employees > 200}} and
then 334 / 3 = 111 for {{s_number_employees < 295}}. Ideally it should return
all 1002 rows for filter {{s_number_employees > 200}}.
In TPC-DS Q79, this causes too less reduce tasks to be spun up causing runtime
delays.
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