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Difference between revisions of "MemoryAnalyzer/OQL"
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Revision as of 13:13, 13 November 2019
Object Query Language
Object Query Language is an SQL like language used by Memory Analyzer for exploring a heap dump.
Simple
SELECT * FROM java.lang.String
Displays all String objects as a tree.
SELECT s as String,s.value as "characters" FROM java.lang.String s
Displays all String objects as a table.
SELECT s as String,s.value as "characters", inbounds(s),inbounds(s).@length FROM java.lang.String s
String |characters |inbounds(s)| inbounds(s).@length -------------------------------------------------------------------------------------------------------------- java.lang.String [id=0x22e58820]|char[] [id=0x22e60f50;length=16;size=48] |[I@620f7a39| 1 java.lang.String [id=0x22e59150]|char[] [id=0x22e62ff0;length=6;size=24] |[I@1f7b8d59| 1 java.lang.String [id=0x22e5b560]|char[] [id=0x22e6b730;length=537;size=1088]|[I@28551755| 1 --------------------------------------------------------------------------------------------------------------
There are two sorts of objects encountered with OQL, IObject which represent Java objects in the snapshot and regular Java objects generated by OQL processing.
java.lang.String [id=0x22e58820] is a IInstance representing a String from the snapshot.
char[] [id=0x22e60f50;length=16;size=48] is an IPrimitiveArray representing a character array from the snapshot.
[I@620f7a39 is a regular Java integer array holding a several of ints which are the object IDs Memory Analyzer uses to represent IObjects in the snapshot.