> > Well, for starters you're looking at an estimation miss. The > exhaustive search found the 'cheaper' plan than what geqo came up > with, but that did not correlate to execution time. This is a common > and frustrating problem. Generally to try and avoid it it's good to > avoid things in tables and queries that the database has difficulty > planning or to crank statistics in specific cases. >
RhodiumToad on #postgresql thinks it may be a different issue -- namely, the fact that there are various estimates of rows=1 when the actual number is higher. Increasing default_statistics_target to 1000 and 10000 seems to confirm this -- if anything, the query runs slower, and the plans look to be about the same. So I'm not convinced yet that it's not a bug. The better performance with geqo on is pretty consistent. I recognize that the query is complex, and I can try to simplify it, but it would be nice if its performance were not a matter of luck. I've attached a file containing the original query and the EXPLAIN ANALYZE results for geqo on and default_statistics_target 100, geqo off and default_statistics_target 100, geqo on and default_statistics_target 10000, and geqo off and default_statistics_target 10000, showing that the increased statistics target doesn't help. (I figured it would be easier to read as an attachment because my email client automatically wraps long lines.) Dave
SELECT ex.ex, ex.lv, ex.tt, ex.td, dnsrc.ex AS trex, ((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) + uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2) AS trq FROM ex INNER JOIN lv ON (lv.lv = ex.lv) INNER JOIN dn ON (dn.ex = ex.ex) INNER JOIN mn ON (mn.mn = dn.mn) INNER JOIN ap ON (ap.ap = mn.ap) INNER JOIN dn AS dn2 ON (dn2.mn = dn.mn) INNER JOIN dn AS dn3 ON (dn3.ex = dn2.ex) INNER JOIN dn AS dnsrc ON (dnsrc.mn = dn3.mn) INNER JOIN mn AS mnsrc ON (mnsrc.mn = dnsrc.mn) INNER JOIN ap AS apsrc ON (apsrc.ap = mnsrc.ap) INNER JOIN ex AS exsrc ON (exsrc.ex = dnsrc.ex) INNER JOIN lv AS lvsrc ON (lvsrc.lv = exsrc.lv) WHERE dn.ex != dn2.ex AND dn3.ex != dnsrc.ex AND mn.ap != mnsrc.ap AND dn.ex != dnsrc.ex AND lcvc(lv.lc, lv.vc) IN ('zul-000') AND lcvc(lvsrc.lc, lvsrc.vc) IN ('gle-000') AND exsrc.tt IN ('doras') GROUP BY ex.ex, dnsrc.ex ORDER BY trq desc LIMIT 2000; EXPLAIN ANALYZE with geqo on and default_statistics_target = 100: QUERY PLAN ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Limit (cost=3603.82..3603.82 rows=2 width=57) (actual time=674.046..674.050 rows=31 loops=1) -> Sort (cost=3603.82..3603.82 rows=2 width=57) (actual time=674.044..674.046 rows=31 loops=1) Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) + uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2)) Sort Method: quicksort Memory: 27kB -> HashAggregate (cost=3603.60..3603.82 rows=2 width=57) (actual time=672.799..674.008 rows=31 loops=1) Group Key: ex.ex, dnsrc.ex -> Nested Loop (cost=3075.23..3603.59 rows=2 width=57) (actual time=8.048..671.384 rows=766 loops=1) -> Nested Loop (cost=3075.17..3603.43 rows=2 width=55) (actual time=8.036..669.963 rows=766 loops=1) Join Filter: (mn.ap <> mnsrc.ap) Rows Removed by Join Filter: 3793 -> Hash Join (cost=3075.08..3603.21 rows=2 width=63) (actual time=8.012..660.229 rows=4559 loops=1) Hash Cond: (dn.ex = ex.ex) -> Nested Loop (cost=3.04..510.58 rows=20564 width=26) (actual time=0.939..553.677 rows=1047985 loops=1) Join Filter: (dn.ex <> dnsrc.ex) Rows Removed by Join Filter: 5396 -> Nested Loop (cost=2.92..277.03 rows=118 width=22) (actual time=0.934..120.245 rows=40543 loops=1) -> Nested Loop (cost=2.87..267.76 rows=118 width=16) (actual time=0.921..62.140 rows=40543 loops=1) -> Hash Join (cost=2.76..266.08 rows=1 width=12) (actual time=0.899..6.318 rows=1254 loops=1) Hash Cond: (exsrc.lv = lvsrc.lv) -> Nested Loop (cost=0.43..263.08 rows=871 width=16) (actual time=0.173..5.788 rows=1516 loops=1) -> Nested Loop (cost=0.34..164.79 rows=871 width=20) (actual time=0.142..1.239 rows=1516 loops=1) -> Nested Loop (cost=0.23..155.09 rows=5 width=12) (actual time=0.101..0.308 rows=43 loops=1) -> Index Scan using ex_tt_idx on ex exsrc (cost=0.11..2.57 rows=2 width=8) (actual time=0.060..0.065 rows=5 loops=1) Index Cond: (tt = 'doras'::text) -> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..75.55 rows=71 width=8) (actual time=0.026..0.045 rows=9 loops=5) Index Cond: (ex = exsrc.ex) -> Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..1.13 rows=81 width=8) (actual time=0.007..0.016 rows=35 loops=43) Index Cond: (mn = dnsrc.mn) Filter: (ex <> dnsrc.ex) Rows Removed by Filter: 1 Heap Fetches: 0 -> Index Scan using mn_pkey on mn mnsrc (cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.003 rows=1 loops=1516) Index Cond: (mn = dnsrc.mn) -> Hash (cost=2.32..2.32 rows=1 width=4) (actual time=0.026..0.026 rows=1 loops=1) Buckets: 1024 Batches: 1 Memory Usage: 1kB -> Index Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1 width=4) (actual time=0.025..0.025 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'gle-000'::bpchar) -> Index Scan using dn_ex_idx on dn dn2 (cost=0.11..0.98 rows=71 width=8) (actual time=0.006..0.040 rows=32 loops=1254) Index Cond: (ex = dn3.ex) -> Index Scan using ap_pkey on ap apsrc (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=40543) Index Cond: (ap = mnsrc.ap) -> Index Only Scan using dn_mn_ex_key on dn (cost=0.11..1.13 rows=81 width=8) (actual time=0.003..0.007 rows=26 loops=40543) Index Cond: (mn = dn2.mn) Filter: (ex <> dn2.ex) Rows Removed by Filter: 1 Heap Fetches: 764 -> Hash (cost=3049.48..3049.48 rows=2149 width=41) (actual time=5.541..5.541 rows=2105 loops=1) Buckets: 1024 Batches: 1 Memory Usage: 121kB -> Nested Loop (cost=0.19..3049.48 rows=2149 width=41) (actual time=0.044..5.110 rows=2105 loops=1) -> Index Scan using lv_lcvc_idx on lv (cost=0.11..2.32 rows=1 width=4) (actual time=0.013..0.014 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'zul-000'::bpchar) -> Index Scan using ex_lv_idx on ex (cost=0.09..3017.95 rows=2921 width=41) (actual time=0.031..4.799 rows=2105 loops=1) Index Cond: (lv = lv.lv) -> Index Scan using mn_pkey on mn (cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1 loops=4559) Index Cond: (mn = dn.mn) -> Index Scan using ap_pkey on ap (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=766) Index Cond: (ap = mn.ap) Planning time: 110.866 ms Execution time: 674.268 ms EXPLAIN ANALYZE with geqo off and default_statistics_target = 100: QUERY PLAN ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Limit (cost=114.58..114.58 rows=1 width=57) (actual time=11155.010..11155.011 rows=31 loops=1) -> Sort (cost=114.58..114.58 rows=1 width=57) (actual time=11155.010..11155.010 rows=31 loops=1) Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) + uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2)) Sort Method: quicksort Memory: 27kB -> HashAggregate (cost=114.47..114.58 rows=1 width=57) (actual time=11153.788..11154.985 rows=31 loops=1) Group Key: ex.ex, dnsrc.ex -> Nested Loop (cost=1.10..114.46 rows=1 width=57) (actual time=6.810..11152.329 rows=766 loops=1) -> Nested Loop (cost=1.05..114.38 rows=1 width=55) (actual time=6.807..11150.787 rows=766 loops=1) Join Filter: (mn.ap <> mnsrc.ap) Rows Removed by Join Filter: 3793 -> Nested Loop (cost=0.96..114.27 rows=1 width=63) (actual time=6.803..11137.899 rows=4559 loops=1) -> Nested Loop (cost=0.90..114.19 rows=1 width=57) (actual time=6.797..11124.582 rows=4559 loops=1) -> Nested Loop (cost=0.85..110.70 rows=27 width=57) (actual time=0.134..3802.781 rows=1047985 loops=1) -> Nested Loop (cost=0.76..107.61 rows=27 width=20) (actual time=0.115..805.442 rows=1047985 loops=1) Join Filter: ((dn.ex <> dn2.ex) AND (dn.ex <> dnsrc.ex)) Rows Removed by Join Filter: 45939 -> Nested Loop (cost=0.65..85.78 rows=11 width=28) (actual time=0.110..231.112 rows=40543 loops=1) -> Nested Loop (cost=0.56..84.54 rows=11 width=20) (actual time=0.102..54.952 rows=40543 loops=1) -> Nested Loop (cost=0.45..82.85 rows=1 width=16) (actual time=0.094..1.056 rows=1254 loops=1) -> Nested Loop (cost=0.33..80.91 rows=1 width=8) (actual time=0.081..0.132 rows=26 loops=1) -> Nested Loop (cost=0.22..4.65 rows=1 width=4) (actual time=0.071..0.073 rows=1 loops=1) -> Index Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1 width=4) (actual time=0.023..0.024 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'gle-000'::bpchar) -> Index Scan using ex_lv_tt_key on ex exsrc (cost=0.11..2.32 rows=1 width=8) (actual time=0.045..0.046 rows=1 loops=1) Index Cond: ((lv = lvsrc.lv) AND (tt = 'doras'::text)) -> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..75.55 rows=71 width=8) (actual time=0.010..0.048 rows=26 loops=1) Index Cond: (ex = exsrc.ex) -> Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..1.13 rows=81 width=8) (actual time=0.004..0.025 rows=48 loops=26) Index Cond: (mn = dnsrc.mn) Filter: (ex <> dnsrc.ex) Rows Removed by Filter: 1 Heap Fetches: 0 -> Index Scan using dn_ex_idx on dn dn2 (cost=0.11..0.98 rows=71 width=8) (actual time=0.005..0.037 rows=32 loops=1254) Index Cond: (ex = dn3.ex) -> Index Scan using mn_pkey on mn (cost=0.09..0.10 rows=1 width=8) (actual time=0.004..0.004 rows=1 loops=40543) Index Cond: (mn = dn2.mn) -> Index Only Scan using dn_mn_ex_key on dn (cost=0.11..1.09 rows=81 width=8) (actual time=0.003..0.008 rows=27 loops=40543) Index Cond: (mn = mn.mn) Heap Fetches: 764 -> Index Scan using ex_pkey on ex (cost=0.09..0.10 rows=1 width=41) (actual time=0.002..0.002 rows=1 loops=1047985) Index Cond: (ex = dn.ex) -> Index Scan using lv_pkey on lv (cost=0.06..0.12 rows=1 width=4) (actual time=0.007..0.007 rows=0 loops=1047985) Index Cond: (lv = ex.lv) Filter: (lcvc(lc, vc) = 'zul-000'::bpchar) Rows Removed by Filter: 1 -> Index Scan using ap_pkey on ap (cost=0.06..0.07 rows=1 width=10) (actual time=0.002..0.002 rows=1 loops=4559) Index Cond: (ap = mn.ap) -> Index Scan using mn_pkey on mn mnsrc (cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1 loops=4559) Index Cond: (mn = dnsrc.mn) -> Index Scan using ap_pkey on ap apsrc (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=766) Index Cond: (ap = mnsrc.ap) Planning time: 163.196 ms Execution time: 11155.197 ms EXPLAIN ANALYZE with geqo on and default_statistics_target = 100: QUERY PLAN ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Limit (cost=2786.77..2786.77 rows=1 width=57) (actual time=790.758..790.761 rows=31 loops=1) -> Sort (cost=2786.77..2786.77 rows=1 width=57) (actual time=790.758..790.761 rows=31 loops=1) Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) + uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2)) Sort Method: quicksort Memory: 27kB -> HashAggregate (cost=2786.65..2786.77 rows=1 width=57) (actual time=789.532..790.738 rows=31 loops=1) Group Key: ex.ex, dnsrc.ex -> Nested Loop (cost=116.90..2786.65 rows=1 width=57) (actual time=627.615..788.824 rows=766 loops=1) -> Nested Loop (cost=116.85..2786.57 rows=1 width=55) (actual time=627.610..787.758 rows=766 loops=1) Join Filter: (mn.ap <> mnsrc.ap) Rows Removed by Join Filter: 3793 -> Hash Join (cost=116.76..2786.46 rows=1 width=63) (actual time=627.601..780.862 rows=4559 loops=1) Hash Cond: (ex.ex = dn.ex) -> Nested Loop (cost=0.19..2668.27 rows=2148 width=41) (actual time=0.028..1.977 rows=2105 loops=1) -> Index Scan using lv_lcvc_idx on lv (cost=0.11..2.32 rows=1 width=4) (actual time=0.014..0.015 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'zul-000'::bpchar) -> Index Scan using ex_lv_idx on ex (cost=0.09..2640.46 rows=2549 width=41) (actual time=0.012..1.642 rows=2105 loops=1) Index Cond: (lv = lv.lv) -> Hash (cost=86.23..86.23 rows=2889 width=26) (actual time=625.609..625.609 rows=1047985 loops=1) Buckets: 1024 Batches: 1 Memory Usage: 61406kB -> Nested Loop (cost=3.04..86.23 rows=2889 width=26) (actual time=0.468..478.534 rows=1047985 loops=1) Join Filter: (dn.ex <> dnsrc.ex) Rows Removed by Join Filter: 5396 -> Nested Loop (cost=2.92..69.60 rows=72 width=22) (actual time=0.465..94.991 rows=40543 loops=1) -> Nested Loop (cost=2.87..63.94 rows=72 width=16) (actual time=0.462..39.185 rows=40543 loops=1) -> Hash Join (cost=2.76..63.53 rows=1 width=12) (actual time=0.454..4.564 rows=1254 loops=1) Hash Cond: (exsrc.lv = lvsrc.lv) -> Nested Loop (cost=0.43..61.01 rows=241 width=16) (actual time=0.058..4.104 rows=1516 loops=1) -> Nested Loop (cost=0.34..33.88 rows=241 width=20) (actual time=0.051..0.773 rows=1516 loops=1) -> Nested Loop (cost=0.23..32.51 rows=6 width=12) (actual time=0.023..0.090 rows=43 loops=1) -> Index Scan using ex_tt_idx on ex exsrc (cost=0.11..2.57 rows=2 width=8) (actual time=0.015..0.019 rows=5 loops=1) Index Cond: (tt = 'doras'::text) -> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..14.84 rows=13 width=8) (actual time=0.006..0.012 rows=9 loops=5) Index Cond: (ex = exsrc.ex) -> Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..0.18 rows=5 width=8) (actual time=0.004..0.011 rows=35 loops=43) Index Cond: (mn = dnsrc.mn) Filter: (ex <> dnsrc.ex) Rows Removed by Filter: 1 Heap Fetches: 0 -> Index Scan using mn_pkey on mn mnsrc (cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1 loops=1516) Index Cond: (mn = dnsrc.mn) -> Hash (cost=2.32..2.32 rows=1 width=4) (actual time=0.008..0.008 rows=1 loops=1) Buckets: 1024 Batches: 1 Memory Usage: 1kB -> Index Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1 width=4) (actual time=0.007..0.007 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'gle-000'::bpchar) -> Index Scan using dn_ex_idx on dn dn2 (cost=0.11..0.28 rows=13 width=8) (actual time=0.004..0.023 rows=32 loops=1254) Index Cond: (ex = dn3.ex) -> Index Scan using ap_pkey on ap apsrc (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=40543) Index Cond: (ap = mnsrc.ap) -> Index Only Scan using dn_mn_ex_key on dn (cost=0.11..0.18 rows=5 width=8) (actual time=0.003..0.006 rows=26 loops=40543) Index Cond: (mn = dn2.mn) Filter: (ex <> dn2.ex) Rows Removed by Filter: 1 Heap Fetches: 764 -> Index Scan using mn_pkey on mn (cost=0.09..0.10 rows=1 width=8) (actual time=0.001..0.001 rows=1 loops=4559) Index Cond: (mn = dn.mn) -> Index Scan using ap_pkey on ap (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=766) Index Cond: (ap = mn.ap) Planning time: 381.122 ms Execution time: 790.886 ms EXPLAIN ANALYZE with geqo off and default_statistics_target = 100: QUERY PLAN ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Limit (cost=22.31..22.31 rows=1 width=57) (actual time=11552.198..11552.200 rows=31 loops=1) -> Sort (cost=22.31..22.31 rows=1 width=57) (actual time=11552.196..11552.196 rows=31 loops=1) Sort Key: (((uiuq_score(array_agg(ap.ui), array_agg(ap.uq)) + uiuq_score(array_agg(apsrc.ui), array_agg(apsrc.uq))) / 2)) Sort Method: quicksort Memory: 27kB -> HashAggregate (cost=22.20..22.31 rows=1 width=57) (actual time=11550.953..11552.178 rows=31 loops=1) Group Key: ex.ex, dnsrc.ex -> Nested Loop (cost=1.10..22.19 rows=1 width=57) (actual time=5.028..11549.670 rows=766 loops=1) -> Nested Loop (cost=1.05..22.12 rows=1 width=55) (actual time=5.025..11548.118 rows=766 loops=1) Join Filter: (mn.ap <> mnsrc.ap) Rows Removed by Join Filter: 3793 -> Nested Loop (cost=0.96..22.00 rows=1 width=63) (actual time=5.022..11535.336 rows=4559 loops=1) -> Nested Loop (cost=0.90..21.92 rows=1 width=57) (actual time=5.016..11521.601 rows=4559 loops=1) -> Nested Loop (cost=0.85..21.41 rows=4 width=57) (actual time=0.084..3902.872 rows=1047985 loops=1) -> Nested Loop (cost=0.76..20.95 rows=4 width=20) (actual time=0.077..898.511 rows=1047985 loops=1) Join Filter: ((dn.ex <> dnsrc.ex) AND (mn.mn = dn.mn)) Rows Removed by Join Filter: 5396 -> Nested Loop (cost=0.65..20.48 rows=2 width=28) (actual time=0.073..210.791 rows=40543 loops=1) -> Nested Loop (cost=0.56..20.26 rows=2 width=20) (actual time=0.065..56.851 rows=40543 loops=1) -> Nested Loop (cost=0.45..19.85 rows=1 width=16) (actual time=0.057..1.095 rows=1254 loops=1) -> Nested Loop (cost=0.33..19.62 rows=1 width=8) (actual time=0.047..0.089 rows=26 loops=1) -> Nested Loop (cost=0.22..4.65 rows=1 width=4) (actual time=0.038..0.040 rows=1 loops=1) -> Index Scan using lv_lcvc_idx on lv lvsrc (cost=0.11..2.32 rows=1 width=4) (actual time=0.021..0.022 rows=1 loops=1) Index Cond: (lcvc(lc, vc) = 'gle-000'::bpchar) -> Index Scan using ex_lv_tt_key on ex exsrc (cost=0.11..2.32 rows=1 width=8) (actual time=0.014..0.015 rows=1 loops=1) Index Cond: ((lv = lvsrc.lv) AND (tt = 'doras'::text)) -> Index Scan using dn_ex_idx on dn dnsrc (cost=0.11..14.84 rows=13 width=8) (actual time=0.008..0.036 rows=26 loops=1) Index Cond: (ex = exsrc.ex) -> Index Only Scan using dn_mn_ex_key on dn dn3 (cost=0.11..0.18 rows=5 width=8) (actual time=0.004..0.027 rows=48 loops=26) Index Cond: (mn = dnsrc.mn) Filter: (ex <> dnsrc.ex) Rows Removed by Filter: 1 Heap Fetches: 0 -> Index Scan using dn_ex_idx on dn dn2 (cost=0.11..0.28 rows=13 width=8) (actual time=0.005..0.038 rows=32 loops=1254) Index Cond: (ex = dn3.ex) -> Index Scan using mn_pkey on mn (cost=0.09..0.10 rows=1 width=8) (actual time=0.003..0.003 rows=1 loops=40543) Index Cond: (mn = dn2.mn) -> Index Only Scan using dn_mn_ex_key on dn (cost=0.11..0.18 rows=5 width=8) (actual time=0.003..0.011 rows=26 loops=40543) Index Cond: (mn = dn2.mn) Filter: (ex <> dn2.ex) Rows Removed by Filter: 1 Heap Fetches: 764 -> Index Scan using ex_pkey on ex (cost=0.09..0.10 rows=1 width=41) (actual time=0.002..0.002 rows=1 loops=1047985) Index Cond: (ex = dn.ex) -> Index Scan using lv_pkey on lv (cost=0.06..0.12 rows=1 width=4) (actual time=0.007..0.007 rows=0 loops=1047985) Index Cond: (lv = ex.lv) Filter: (lcvc(lc, vc) = 'zul-000'::bpchar) Rows Removed by Filter: 1 -> Index Scan using ap_pkey on ap (cost=0.06..0.07 rows=1 width=10) (actual time=0.002..0.002 rows=1 loops=4559) Index Cond: (ap = mn.ap) -> Index Scan using mn_pkey on mn mnsrc (cost=0.09..0.10 rows=1 width=8) (actual time=0.002..0.002 rows=1 loops=4559) Index Cond: (mn = dnsrc.mn) -> Index Scan using ap_pkey on ap apsrc (cost=0.06..0.07 rows=1 width=10) (actual time=0.001..0.001 rows=1 loops=766) Index Cond: (ap = mnsrc.ap) Planning time: 434.082 ms Execution time: 11552.325 ms
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