Hibernate嵌套的一对多关联

Question

我有具有以下关联的类Polygon，LineString，Point：

• 多边形-LineString是一对多关系（例如，polygon.getLineStrings（））
• LineString-点是一对多关系（例如lineString.getPoints（））

我想检索与Polygon相关的所有数据：其值类型，其LineString和每个LineString的磅。 理想情况下，应使用JOIN提取策略在单个查询中完成。

考虑以下数据库装置：

Polygon1
|-LineString1
  |-Point1
  |-Point2
  |-Point3
|-LineString2
  |-Point4
  |-Point5

以下查询正确检索LineStrings。 之后，将为每个LineString检索点，效率不高：

from Polygon as p join fetch p.lineStrings as l

以下查询检索5个LineString（多达Point），这是不正确的：

select Polygon as p join fetch p.lineStrings as l join fetch l.points

但是，生成的查询看起来不错：

select polygonent0_.ID as ID1_23_0_, linestring2_.ID as ID1_14_1_, pointentit4_.ID as ID1_22_2_, polygonent0_.POLYGONID as POLYGONI2_23_0_, polygonent0_.POLYGONTYPE as POLYGONT3_23_0_, polygonent0_.POLYGONDESIGNATOR as POLYGOND4_23_0_, polygonent0_.POLYGONAREA as POLYGONA5_23_0_, polygonent0_.POLYGONCOLOUR as POLYGONC6_23_0_, linestring2_.LINESTRINGID as LINESTRI2_14_1_, linestring2_.LINESTRINGTYPE as LINESTRI3_14_1_, linestring2_.LINESTRINGDESIGNATOR as LINESTRI4_14_1_, linestring2_.LINESTRINGWIDTH as LINESTRI5_14_1_, linestring2_.LINESTRINGLENGTH as LINESTRI6_14_1_, linestring2_.LINESTRINGCOLOUR as LINESTRI7_14_1_, linestring1_.POLYGONIDREF as POLYGONI1_23_0__, linestring1_.LINESTRINGIDREF as LINESTRI2_24_0__, pointentit4_.POINTID as POINTID2_22_2_, pointentit4_.POINTTYPE as POINTTYP3_22_2_, pointentit4_.POINTDESIGNATOR as POINTDES4_22_2_, pointentit4_.POINTNORTH as POINTNOR5_22_2_, pointentit4_.POINTEAST as POINTEAS6_22_2_, pointentit4_.POINTUP as POINTUP7_22_2_, pointentit4_.POINTCOLOUR as POINTCOL8_22_2_, pointentit4_.POINTHORIZONTALACCURACY as POINTHOR9_22_2_, pointentit4_.POINTVERTICALACCURACY as POINTVE10_22_2_, pointentit4_.FILENAME as FILENAM11_22_2_, pointentit4_.FILELENGTH as FILELEN12_22_2_, points3_.LINESTRINGIDREF as LINESTRI1_14_1__, points3_.POINTIDREF as POINTIDR2_15_1__, points3_.idx as idx3_1__ 
from POLYGON polygonent0_ 
inner join POLYGON_LINESTRING linestring1_ on polygonent0_.ID=linestring1_.POLYGONIDREF 
inner join LINESTRING linestring2_ on linestring1_.LINESTRINGIDREF=linestring2_.ID 
inner join LINESTRING_POINT points3_ on linestring2_.ID=points3_.LINESTRINGIDREF 
inner join POINT pointentit4_ on points3_.POINTIDREF=pointentit4_.ID 
where polygonent0_.ID=? 

任何帮助是极大的赞赏。

Answer 1

乍一看，我发现您正在为多边形和点重复使用相同的别名“ p”。 您能给他们不同的别名吗？