[DERBY-5487] Primary key disk pages not reclaimed when using SYSCS_UTIL.SYSCS_COMPRESS_TABLE with just the purge_rows option

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 10.8.1.2
• Component/s: Store
• Labels: derby_triage10_8
• Environment: Windows 7, Embedded Derby mode
• Urgency: Normal
• Issue & fix info: Repro attached
• Bug behavior facts: Performance
• Assignee: Unassigned
• Reporter: Sundar Narayanaswamy
• Created: 29/Oct/11 04:30
• Updated: 23/Sep/17 21:37

Description

When I continuously insert data, delete the inserted data then compress with purge_rows option in a loop, space is not reclaimed from the primary key file. The inserts are committed every 10000 rows, deletes committed every 50000 rows. All the rows that were inserted are deleted. The primary key values continually increase (across the inserts) . All the activities occur on a single thread. Included below is the space table output after each iteration in the loop:

As can be seen below and in the screenshot attached, the NumAllocatedpages for SQL111029001155930 is continuously increasing. This increase does not happen if the primary key values are reset after each iteration (ie, primary key values for new inserts are in the same range as deleted rows).

Iteration: 0
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 803 1 4096 3289088
SQL111029003533400 1 238 31 179 4096 126976
LOC_INDEX 1 211 185 119 4096 757760
Database size: 12993 KB

Iteration: 1
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 816 1 4096 3342336
SQL111029003533400 1 324 192 200 4096 786432
LOC_INDEX 1 1 406 1 4096 1662976
Database size: 17112 KB

Iteration: 2
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 7 810 1 4096 3317760
SQL111029003533400 1 579 23 294 4096 94208
LOC_INDEX 1 394 28 2 4096 114688
Database size: 22821 KB

Iteration: 3
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 816 0 4096 3342336
SQL111029003533400 1 631 227 451 4096 929792
LOC_INDEX 1 5 437 3 4096 1789952
Database size: 18054 KB

Iteration: 4
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 735 174 460 4096 712704
LOC_INDEX 1 1 441 1 4096 1806336
Database size: 15632 KB

Iteration: 5
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 4 814 0 4096 3334144
SQL111029003533400 1 992 21 690 4096 86016
LOC_INDEX 1 378 64 127 4096 262144
Database size: 25633 KB

Iteration: 6
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 1071 199 744 4096 815104
LOC_INDEX 1 5 437 3 4096 1789952
Database size: 19763 KB

Iteration: 7
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 1320 29 932 4096 118784
LOC_INDEX 1 395 47 11 4096 192512
Database size: 26911 KB

Iteration: 8
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 1421 177 1014 4096 724992
LOC_INDEX 1 1 441 1 4096 1806336
Database size: 21003 KB

Iteration: 9
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 1593 106 1063 4096 434176
LOC_INDEX 1 1 441 1 4096 1806336
Database size: 29662 KB

Iteration: 10
ConglomerateName IsIndex NumAllocatedPages NumFreePages NumUnFilledPages PageSize EstimSpaceSaving
LOCATION 0 1 817 0 4096 3346432
SQL111029003533400 1 1736 135 1083 4096 552960
LOC_INDEX 1 3 439 2 4096 1798144
Database size: 22035 KB

------------------ Java Information ------------------
Java Version: 1.6.0_21
Java Vendor: Sun Microsystems Inc.
Java home: c:\development\
Java classpath: .;derby-10.8.1.2.jar
OS name: Windows 7
OS architecture: x86
OS version: 6.1
Java user name: testuser
Java user home: C:\Users\testuser
Java user dir: C:\temp\Derby
java.specification.name: Java Platform API Specification
java.specification.version: 1.6
java.runtime.version: 1.6.0_21-b06
--------- Derby Information --------
JRE - JDBC: Java SE 6 - JDBC 4.0
[C:\temp\Derby\derby-10.8.1.2.jar] 10.8.1.2 - (1095077)
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----------------- Locale Information -----------------
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Issue Links

• is related to: DERBY-5876 Overhaul table compression code