- svv_table_info.skew_rows （スライス単位での最大行数/最小行数）の値が大きいと偏っている。
=# select * from svv_table_info where "table" = 'lineitem_dk_shipdate1';
-[ RECORD 1 ]
database | tpch_3tb_skew_distkey
schema | public
table_id | 111347
table | lineitem_dk_shipdate1
encoded | Y, AUTO(ENCODE)
diststyle | KEY(l_shipdate)
sortkey1 | l_shipdate
max_varchar | 44
sortkey1_enc | none
sortkey_num | 2
size | 953627
pct_used | 0.1862
empty | 0
unsorted | 0.44
stats_off | 0.00
tbl_rows | 18080048306
skew_sortkey1 | 3.35
skew_rows | 1.29 ★
estimated_visible_rows | 18080047104
risk_event |
vacuum_sort_benefit | 0.00
- stv_tbl_perm.rows でスライス毎の行数を確認できる。
=# select * from stv_tbl_perm where name = 'lineitem_dk_shipdate1' order by slice;
slice | id | name | rows★ | sorted_rows | temp | db_id | insert_pristine | delete_pristine | backup | dist_style | block_count
0 | 111347 | lineitem_dk_shipdate1 | 1105831627 | 1105831627 | 0 | 110787 | 0 | 1 | 1 | 1 | 58332
1 | 111347 | lineitem_dk_shipdate1 | 1205274176 | 1205274176 | 0 | 110787 | 0 | 1 | 1 | 1 | 63588
2 | 111347 | lineitem_dk_shipdate1 | 1122205096 | 1122205096 | 0 | 110787 | 0 | 1 | 1 | 1 | 59151
3 | 111347 | lineitem_dk_shipdate1 | 1318458166 | 1318458166 | 0 | 110787 | 0 | 1 | 1 | 1 | 69562
4 | 111347 | lineitem_dk_shipdate1 | 1191046470 | 1111046470 | 0 | 110787 | 0 | 1 | 1 | 1 | 62940
5 | 111347 | lineitem_dk_shipdate1 | 1107365471 | 1107365471 | 0 | 110787 | 0 | 1 | 1 | 1 | 58409
6 | 111347 | lineitem_dk_shipdate1 | 1145335102 | 1145335102 | 0 | 110787 | 0 | 1 | 1 | 1 | 60410
7 | 111347 | lineitem_dk_shipdate1 | 1023442529 | 1023442529 | 0 | 110787 | 0 | 1 | 1 | 1 | 53997
8 | 111347 | lineitem_dk_shipdate1 | 1090088206 | 1090088206 | 0 | 110787 | 0 | 1 | 1 | 1 | 57473
9 | 111347 | lineitem_dk_shipdate1 | 1140357965 | 1140357965 | 0 | 110787 | 0 | 1 | 1 | 1 | 60123
10 | 111347 | lineitem_dk_shipdate1 | 1128260563 | 1128260563 | 0 | 110787 | 0 | 1 | 1 | 1 | 59512
11 | 111347 | lineitem_dk_shipdate1 | 1044099754 | 1044099754 | 0 | 110787 | 0 | 1 | 1 | 1 | 55074
12 | 111347 | lineitem_dk_shipdate1 | 1071680574 | 1071680574 | 0 | 110787 | 0 | 1 | 1 | 1 | 56517
13 | 111347 | lineitem_dk_shipdate1 | 1014295796 | 1014295796 | 0 | 110787 | 0 | 1 | 1 | 1 | 53462
14 | 111347 | lineitem_dk_shipdate1 | 1183561831 | 1183561831 | 0 | 110787 | 0 | 1 | 1 | 1 | 62405
15 | 111347 | lineitem_dk_shipdate1 | 1188744980 | 1188744980 | 0 | 110787 | 0 | 1 | 1 | 1 | 62672
12814 | 111347 | lineitem_dk_shipdate1 | 0 | 0 | 0 | 110787 | 3 | 1 | 1 | 1 | 0
