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Type:
Task
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Resolution: Unresolved
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: None
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Query Execution
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15
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One of the areas in which SBE's performance can be improved is by eliminating repeated path traversals. This is evident in $or queries such as:
"$or" : [
{
"a" : 1,
"b" : 2
},
{
"a" : 2,
"b" : 3
}
]
The SBE plan is as follows:
[1] filter {s30}
[1] nlj [s4, s5] [s4, s5]
left
[1] scan s4 s5 none none none none [] @"7b34d685-f43c-4e59-86ad-bdf5f77c6234" true false
right
[1] limit 1
[1] union [s30] [
[s28] [1] project [s28 = true]
[1] filter {s16}
[1] limit 1
[1] union [s16] [
[s14] [1] project [s14 = false]
[1] filter {! fillEmpty (s9, false)}
[1] traverse s9 s8 s6 {s9 || s8} {s9} 1
from
[1] project [s6 = getField (s4, "a")]
[1] limit 1
[1] coscan
in
[1] project [s8 = fillEmpty (s6 == s7, false)]
[1] limit 1
[1] coscan
,
[s15] [1] project [s15 = fillEmpty (s13, false)]
[1] traverse s13 s12 s10 {s13 || s12} {s13} 1
from
[1] project [s10 = getField (s4, "b")]
[1] limit 1
[1] coscan
in
[1] project [s12 = fillEmpty (s10 == s11, false)]
[1] limit 1
[1] coscan ] ,
[s29] [1] project [s29 = s27]
[1] limit 1
[1] union [s27] [
[s25] [1] project [s25 = false]
[1] filter {! fillEmpty (s20, false)}
[1] traverse s20 s19 s17 {s20 || s19} {s20} 1
from
[1] project [s17 = getField (s4, "a")]
[1] limit 1
[1] coscan
in
[1] project [s19 = fillEmpty (s17 == s18, false)]
[1] limit 1
[1] coscan
,
[s26] [1] project [s26 = fillEmpty (s24, false)]
[1] traverse s24 s23 s21 {s24 || s23} {s24} 1
from
[1] project [s21 = getField (s4, "b")]
[1] limit 1
[1] coscan
in
[1] project [s23 = fillEmpty (s21 == s22, false)]
[1] limit 1
[1] coscan ]
]
In the above plan, we perform multiple getField lookups for "a" and "b", one for each branch of the $or. This ticket tracks to investigate eliminating such repeated path lookups when constructing SBE plans (credit to nikita.lapkov@mongodb.com for the idea!)
- related to
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SERVER-69510 Make SBE Stage Builder for match expressions use ABT
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- Closed
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- Closed
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