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b3d8a507cb
Adds the TABLESAMPLE clause for COMPUTE STATS.
Syntax:
COMPUTE STATS <table> TABLESAMPLE SYSTEM(<number>) [REPEATABLE(<number>)]
Computes and replaces the table-level row count and total file size,
as well as all table-level column statistics. Existing partition-level
row counts are not modified.
The TABLESAMPLE clause can be used to limit the scanned data volume to
a desired percentage. When sampling, the unmodified results of the
COMPUTE STATS queries are sent to the CatalogServer. There, the stats
are extrapolated before storing them into the HMS so as not to confuse
other engines like Hive/SparkSQL which may rely on the shared HMS
fields being accurate.
Limitations
- Only works for HDFS tables
- TABLESAMPLE is not supported for COMPUTE INCREMENTAL STATS
- TABLESAMPLE requires --enable_stats_extrapolation=true
Changes to EXPLAIN
The stored statistics from the HMS are more clearly displayed under
a 'stored statistics' section. Example:
00:SCAN HDFS [functional.alltypes, RANDOM]
partitions=24/24 files=24 size=478.45KB
stored statistics:
table: rows=7300 size=478.45KB
partitions: 24/24 rows=7300
columns: all
Testing:
- added new functional tests
- core/hdfs run passed
Change-Id: I7f3e72471ac563adada4a4156033a85852b7c8b7
Reviewed-on: http://gerrit.cloudera.org:8080/8136
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: Impala Public Jenkins
194 lines
7.2 KiB
Plaintext
194 lines
7.2 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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' stored statistics:'
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' table: rows=unavailable size=unavailable'
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' partitions: 0/12 rows=unavailable'
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' columns: unavailable'
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' extrapolated-rows=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 1 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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# Only the table-level row count is stored. The partition row counts are extrapolated.
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show table stats alltypes
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---- LABELS
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YEAR, MONTH, #ROWS, EXTRAP #ROWS, #FILES, SIZE, BYTES CACHED, CACHE REPLICATION, FORMAT, INCREMENTAL STATS, LOCATION
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---- RESULTS
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'2009','1',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=1'
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'2009','2',-1,288,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=2'
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'2009','3',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=3'
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'2009','4',-1,302,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=4'
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'2009','5',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=5'
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'2009','6',-1,302,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=6'
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'2009','7',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=7'
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'2009','8',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=8'
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'2009','9',-1,302,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=9'
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'2009','10',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=10'
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'2009','11',-1,302,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=11'
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'2009','12',-1,308,1,regex:.*B,'NOT CACHED','NOT CACHED','PARQUET','false','$NAMENODE/test-warehouse/$DATABASE.db/alltypes/year=2009/month=12'
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'Total','',3650,3650,12,regex:.*B,'0B','','','',''
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---- TYPES
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STRING,STRING,BIGINT,BIGINT,BIGINT,STRING,STRING,STRING,STRING,STRING,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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'Max Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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'Codegen disabled by planner'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'| Per-Host Resources: mem-estimate=16.00MB mem-reservation=0B'
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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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' stored statistics:'
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row_regex:.*table: rows=3650 size=.*
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' partitions: 0/12 rows=unavailable'
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' columns: all'
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' extrapolated-rows=3650'
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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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'Max Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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'Codegen disabled by planner'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'| Per-Host Resources: mem-estimate=16.00MB mem-reservation=0B'
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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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' stored statistics:'
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row_regex:.*table: rows=3650 size=.*
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' partitions: 0/3 rows=unavailable'
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' columns: all'
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' extrapolated-rows=904'
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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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'Max 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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'| Per-Host Resources: mem-estimate=16.00MB mem-reservation=0B'
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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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' stored statistics:'
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row_regex:.*table: rows=3650 size=.*
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' partitions: 0/12 rows=unavailable'
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' columns: all'
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' extrapolated-rows=7300'
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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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'Max Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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'Codegen disabled by planner'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'| Per-Host Resources: mem-estimate=16.00MB mem-reservation=0B'
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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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' stored statistics:'
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row_regex:.*table: rows=3650 size=.*
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' partitions: 0/12 rows=unavailable'
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' columns: all'
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' extrapolated-rows=3651'
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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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'Max Per-Host Resource Reservation: Memory=0B'
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'Per-Host Resource Estimates: Memory=16.00MB'
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'Codegen disabled by planner'
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''
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'F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1'
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'| Per-Host Resources: mem-estimate=16.00MB mem-reservation=0B'
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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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' stored statistics:'
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row_regex:.*table: rows=10950 size=.*
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' partitions: 0/12 rows=unavailable'
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' columns: all'
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' extrapolated-rows=3651'
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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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' stored statistics:'
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' table: rows=unavailable size=unavailable'
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' partitions: 0/24 rows=unavailable'
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' columns: unavailable'
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' extrapolated-rows=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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