Memory Analysis Tool OQL 用例汇总及语法学习

典型用例

• 获取所有对象:

  SELECT * FROM ${snapshot}.getClasses()
  SELECT * FROM (SELECT * FROM java.lang.Class)

• 获取所有java.lang.Thread的对象及子对象:

  SELECT * FROM INSTANCEOF java.lang.Thread

• 获取Thread的对象的引用，用于引用链分析:

  SELECT OBJECTS outbounds(t) FROM INSTANCEOF java.lang.Thread t WHERE toHex(t.@objectAddress).equals("0x40a35490")

• 获取Thread的对象的objectId:

  SELECT t.@objectId FROM INSTANCEOF java.lang.Thread t 

• 利用objectId查看对象的引用链:

  SELECT OBJECTS outbounds(t) FROM OBJECTS 411 t 
  

• 获取所有根节点:

  SELECT OBJECTS ${snapshot}.getGCRoots() FROM OBJECTS 0x0

• 根节点中的java.lang.String:

  SELECT t, t.@retainedHeapSize FROM java.lang.String t WHERE (t  IN  (SELECT OBJECTS ${snapshot}.getGCRoots() FROM OBJECTS 0x0 ))

• 按线程级别分析内存占用(用于指导是否采用Thread-Local-Heap):

  SELECT t.@retainedHeapSize, toString(t) FROM INSTANCEOF java.lang.Thread t 
  

• 获取某个对象的引用对象集合

  SELECT AS RETAINED SET * FROM OBJECTS 410

   

基本语法

• 结构
  

  SELECT *
  FROM [ INSTANCEOF ] <class name>
  [ WHERE <filter-expression> ]

• SELECT
• FROM
• WHERE
• 内置函数调用