Selectivity Estimation in Spatial Databases

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Selectivity Estimation in Spatial Databases

• S. Acharya, V. Poosala, S. Ramaswamy
• Presented By Eyal Flato

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????

• ????? - ???? ????? ????????? ???????? ??????
• ??????? ???????
• ???????? Min-Skew
• ?????? ???????
• ??????

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???? ?????

• GIS - Geographic Information System??????
  ???????? ESRI ARC/INFO, MapInfoDB ?? ?????
  ???????? Informix, Oracle
• Selectivity Estimation - ????? ???? ????????
  ??????? ??????? - ???? ?- query optimizers-
  ????? ??? ????? ?????? - ???? ??????- ???????
  ???????? ?? ????? ???? ???????

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???? ????? - ?????
5
??????? ??????

• ?????????
• ?????
• ???? ?????? ?????? ????? ?? ???? ??? ?? ??????
• ????? ???? ????? ??????? ?-buckets, ?????
  ??????? ??? ???? ??????? ?? ?-buckets

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Spatial v. Traditional

• ???????? ?-DB ?????? ????? ???? ????? ?????
• ??????? ?????? ????? ?? ?????? ??? ?????(?????
  ??? ??????? ??????)
• ?????? (????? ?????) ??????? ????? ????

Q
in Q ?
of Milk ?
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????? ?????

• ?? ????? ????? ?? ????? ????? ??? (????? ??????)
• ??????? ???? ????

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???????

• T - ???? ???????
• Area(T) - ??? ????? ????? ?? ?? ???????
• TA - ???? ?????? ?? ?? ????????
• Q - ???? ???????
• selectivity of Q - ???? ?????? ??????? ?????
  ????? ????????
• Vavg, Havg - ???? ????? ????? ??????? ?-T

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????? ?????

• ????? ???? ?? ?? ???? ????????? ????? ???????
• ??? ?????? ????? ??? ??? ????? ??????

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Uniformity Assumption

• Point Query - ??? ??????? ???? ??????
• TA / Area(T)
• ?? ???? ??????? ????? ???? ?????
• Range Query - ?????? ?????? ???? ???? ?????
  ?????? ???????? ????? ???? ????
• nArea(Q) / Area(T)
• Q - ????? ?? ??????? ???? ????? ??????

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????? ???? ???????

• ???????? ?????? ????? ??????? ?? ????? ????
  ??????? - ???? ??????? ???? ????
• ???? ????? ??????? ??????? ?????? ???????
  ???????? ?? ?????? ??????? ??????? ?????

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15
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????? ??????? ?????

• Equi-Area - ?????? ????? ????.
• ?????? ????? ???????? ?? ?????? ????????? ???????
  (??? ??? ???? ????? ?????)
• ????? ?????? ?? ???? ???????

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????? ??????? ?????

• Equi-Count - ??? ???? ???? ???? ?? ???????.
• ?????? ????? ???????? ?? ?????? ????????? ???????
  (??? ???? ??????? ????? ?????)
• ????? ?????? ??????, ???? ?????? ?? ?? ????

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?????? ??? ?????? R-Tree

• ????? ?????? ??? ??? ?? ???? ????? ???? ????
  ????? ?? ?? ??????????-??? ???
• ???? ??? ??????/ ?? 2-3
• ????? ?? ????? ??? ??? ?????????? ????? ??????
  ????? ???????? ?? ????, ????? ???

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??????? ?? ?????? ????? ?-R-Tree

• ????Equi-Area - ?? ?????? ???????? ??????
  ????????Equi-Count - ????? ???? ?????? ???????
  ??????, ?? ?? ???????? ????? - ?? ?????R-Tree -
  ????? ???? ?????? ?? ??????

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??????? ?? ?????? ????? ?-R-Tree

• ??? ?????Equi-Area, Equi-Count - ???? ?????? ??
  ???? ??????? ???? ??????R-Tree - ??? ????? ???

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???????? Min-Skew

• ?????
• ????? ?????? ????? - ???????? ????? ???????? ????
• ????? ???? ??????? ??????? ?????
• ????? ?? ???? ?????? ???? ????
• ????? ?? ?????? ???? ?? ??? ?????

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???????? Min-Skew

• ????????? ????? ???? ????? ???????
• 1. ????? ??????? ?? ???? ????? ?????? ???????
  ?????? ?? ??? ?? ?????? ???????
• 2. ???????? greedy ?????? ??????

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???????? Min-Skew????? ????

• ????? ?-grid ????? ????? ???? ???? ???????
• ???? ??? ?? ???? ?????? ?? ???? ???????? ?????
  ??? ??? ?????? ?-grid - ?????? ??????
• ???? ???? ???? ?? ????????? ???? ?-grid ?????
  ??????? ??????? ??? ?? ??.

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???????? Min-Skew ????? ??????

• ??? ???? Bi ?????? ????? spatial skew
• Si ?????? ?? ???? ??????? ??????? ?? ??????
  ?-grid ??????? ???? Bi
• ??????? ?????
• (Ni ???? ?????? ?-grid ????? Bi)
• ????? ????? ?????? ???????? ?? ??????? ?????
• ????????? ??? Binary Space Partition

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1
0
1
2
3
2
1
Bi
0
5
1
3
2
1
1
1
Ni 6 Si 2.3
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???????? Min-Skew ????? ??????

• ??? ?????? grid ?? ?????? ?????? ??? ??
• ????? ????? ???? ????? ?? ?? ???? ??????
• ?? ??? ?? ???? ?????? ??????

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?????? ???????

• ????? ??????? ?????? ?????? ?? ?????? ???????
  ?????????
• ??? ?????? ?????? - ????? ????? ?????? ??
  ???????? ????? ?????? ??????? ?? ??????? ???????

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?????? ???????????? ???? ???????
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?????? ???????????? ???? ??????? ?????
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?????? ???????????? ?????? ?-grid ?? Min-Skew
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????? Min-SkewProgressive Refinement

• ????? ???????? ?????? ????? ????? ???? ?? ???
  ?????? ?????? ?-grid

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?????Progressive Refinement
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???? ????
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??????

• ?????? ??????? ?- selectivity estimation (?????,
  ?????????) ?? ??????? ?-DB ???????? (?????)
• ????? ???????? ????? ???????? ?????? ?????? ?????
  ?? ?? ?????? ????? ???
• ???????? Min-Skew ???? ?? ??? ???????? ??????
  ????? ????? ???? ????? ????

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