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e89d7057a6
The main idea of this patch is to use table stats to extrapolate the row counts for new/modified partitions. Existing behavior: - Partitions that lack the row count stat are ignored when estimating the cardinality of HDFS scans. Such partitions effectively have an estimated row count of zero. - We always use the row count stats for partitions that have one. The row count may be innaccurate if data in such partitions has changed significantly. Summary of changes: - Enhance COMPUTE STATS to also store the total number of file bytes in the table. - Use the table-level row count and file bytes stats to estimate the number of rows in a scan. - A new impalad startup flag is added to enable/disable the extrapolation behavior. The feature is disabled by default. Note that even with the feature disabled, COMPUTE STATS stores the file bytes so you can enable the feature without having to run COMPUTE STATS again. Testing: - Added new FE unit test - Added new EE test Change-Id: I972c8a03ed70211734631a7dc9085cb33622ebc4 Reviewed-on: http://gerrit.cloudera.org:8080/6840 Reviewed-by: Alex Behm <alex.behm@cloudera.com> Tested-by: Impala Public Jenkins
149 lines
4.4 KiB
Plaintext
149 lines
4.4 KiB
Plaintext
====
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---- QUERY
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create table alltypes like functional_parquet.alltypes;
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insert into alltypes partition(year, month)
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select * from functional_parquet.alltypes where year = 2009;
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====
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---- QUERY
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# No stats are available.
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explain select id from alltypes;
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---- RESULTS: VERIFY_IS_SUBSET
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' stats-rows=unavailable extrapolated-rows=unavailable'
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' table stats: rows=unavailable size=unavailable'
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' column stats: unavailable'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=unavailable'
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---- TYPES
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STRING
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====
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---- QUERY
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compute stats alltypes
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---- RESULTS
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'Updated 12 partition(s) and 11 column(s).'
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---- TYPES
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STRING
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====
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---- QUERY
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# Stats are available now.
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explain select id from alltypes;
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---- RESULTS: VERIFY_IS_EQUAL
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'Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'PLAN-ROOT SINK'
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'| mem-estimate=0B mem-reservation=0B'
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'|'
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'00:SCAN HDFS [$DATABASE.alltypes]'
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row_regex:.*partitions=12/12 files=12 size=.*
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' stats-rows=3650 extrapolated-rows=3650'
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row_regex:.*table stats: rows=3650 size=.*
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' column stats: all'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=3650'
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---- TYPES
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STRING
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====
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---- QUERY
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# Select a subset of partitions.
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explain select id from alltypes where month in (1, 2, 3);
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---- RESULTS: VERIFY_IS_EQUAL
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'Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'PLAN-ROOT SINK'
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'| mem-estimate=0B mem-reservation=0B'
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'|'
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'00:SCAN HDFS [$DATABASE.alltypes]'
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row_regex:.*partitions=3/12 files=3 size=.*
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' stats-rows=900 extrapolated-rows=904'
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row_regex:.*table stats: rows=3650 size=.*
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' column stats: all'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=904'
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---- TYPES
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STRING
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====
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---- QUERY
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# Double the data in existing partitions.
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insert into alltypes partition(year, month)
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select * from functional_parquet.alltypes where year = 2009;
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explain select id from alltypes;
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---- RESULTS: VERIFY_IS_EQUAL
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'Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'PLAN-ROOT SINK'
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'| mem-estimate=0B mem-reservation=0B'
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'|'
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'00:SCAN HDFS [$DATABASE.alltypes]'
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row_regex:.*partitions=12/12 files=24 size=.*
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' stats-rows=3650 extrapolated-rows=7300'
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row_regex:.*table stats: rows=3650 size=.*
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' column stats: all'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=7300'
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---- TYPES
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STRING
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====
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---- QUERY
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# Create new partitions and extrapolate their row count.
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insert into alltypes partition(year, month)
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select * from functional_parquet.alltypes where year = 2010;
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explain select id from alltypes where year = 2010;
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---- RESULTS: VERIFY_IS_EQUAL
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'Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'PLAN-ROOT SINK'
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'| mem-estimate=0B mem-reservation=0B'
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'|'
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'00:SCAN HDFS [$DATABASE.alltypes]'
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row_regex:.*partitions=12/24 files=12 size=.*
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' stats-rows=unavailable extrapolated-rows=3651'
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row_regex:.*table stats: rows=3650 size=.*
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' column stats: all'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=3651'
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---- TYPES
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STRING
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====
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---- QUERY
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# Compute stats and run the same query again.
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compute stats alltypes;
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explain select id from alltypes where year = 2010;
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---- RESULTS: VERIFY_IS_EQUAL
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'Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'PLAN-ROOT SINK'
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'| mem-estimate=0B mem-reservation=0B'
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'|'
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'00:SCAN HDFS [$DATABASE.alltypes]'
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row_regex:.*partitions=12/24 files=12 size=.*
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' stats-rows=3650 extrapolated-rows=3651'
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row_regex:.*table stats: rows=10950 size=.*
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' column stats: all'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=3651'
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---- TYPES
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STRING
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====
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---- QUERY
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# Test that dropping stats resets everything.
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drop stats alltypes;
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explain select id from alltypes;
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---- RESULTS: VERIFY_IS_SUBSET
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' stats-rows=unavailable extrapolated-rows=unavailable'
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' table stats: rows=unavailable size=unavailable'
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' column stats: unavailable'
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' mem-estimate=16.00MB mem-reservation=0B'
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' tuple-ids=0 row-size=4B cardinality=unavailable'
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---- TYPES
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STRING
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====
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