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MemoryAnalyzer/OQL

< MemoryAnalyzer
Revision as of 13:12, 13 November 2019 by Andrew johnson.uk.ibm.com (Talk | contribs) (Created page with "== Object Query Language == Object Query Language is an SQL like language used by Memory Analyzer for exploring a heap dump. Simple <code> SELECT * FROM java.lang.String <...")

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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.

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