Joins vs. Plans (Interesting orders)
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SELECT R.b FROM R,S,T WHERE R.a = S.a and S.b = T.b; SELECT R.b FROM R,S,T WHERE R.a = S.a and S.b = T.b ORDER BY R.b ; Joins vs. Plans (Interesting orders) T T.b DC RS S.b DC DC R.a R S.a DC S.b S ST S.a DC RST DC In-memory directory Number of Joins = 4 Number of Plans = 12 15 R.b R.b R.b R S S T R ST RS T 2 join partitions Order on R.a is interesting (useful) for Merge-join with S
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RST. DC. R.b. 2 join partitions. ST. S.a. DC. R. RS. R. S. T. T. S. ST. S.b. RS. DC. R.b. T.b. DC. T. S. S.b. S.a. DC. R. R.b. DC. R.a. Joins vs. Plans (Interesting orders). In-memory directory. SELECT R.b FROM R,S,T WHERE R.a = S.a and - PowerPoint PPT Presentation
Transcript of Joins vs. Plans (Interesting orders)
SELECT R.bFROM R,S,TWHERE R.a = S.a and S.b = T.b;
SELECT R.bFROM R,S,TWHERE R.a = S.a and S.b = T.bORDER BY R.b ;
Joins vs. Plans (Interesting orders)
T T.bDC
RS S.bDC
DC R.aR
S.aDC S.bS
ST S.aDC
RST DC
In-memory directory
Number of Joins = 4Number of Plans = 1215
R.b
R.b
R.b
R SS T
R ST
RS T
2 join partitions
Order on R.a is interesting (useful) for Merge-join with S
