fix memory problems

[jvillafanez]

Description

Excessive memory usage caused by several variables not being cleaned.
Related to #35094

Related Issue

https://github.com/owncloud/enterprise/issues/2925

Motivation and Context

Memory used by those variables can be reclaimed and reused once those variables aren't needed any longer.

How Has This Been Tested?

• test environment:
• test case 1:
• test case 2:
• ...

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

Open tasks:

• Backport (if applicable set "backport-request" label and remove when the backport was done)

[VicDeo]

Looks good

[codecov]

Codecov Report

Merging #35612 into master will increase coverage by 0.21%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master   #35612      +/-   ##
============================================
+ Coverage     65.47%   65.68%   +0.21%     
+ Complexity    18776    18775       -1     
============================================
  Files          1222     1222              
  Lines         70871    70932      +61     
  Branches       1289     1289              
============================================
+ Hits          46405    46595     +190     
+ Misses        24088    23959     -129     
  Partials        378      378

Flag	Coverage Δ	Complexity Δ
#javascript	53.7% <ø> (ø)	0 <ø> (ø)	⬇️
#phpunit	67.06% <100%> (+0.23%)	18775 <0> (-1)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
lib/private/legacy/hook.php	79.41% <ø> (+2.26%)	17 <0> (ø)	⬇️
lib/private/Preview.php	80.16% <100%> (+0.04%)	178 <0> (ø)	⬇️
apps/dav/lib/Connector/Sabre/Node.php	75% <0%> (-6.15%)	49% <0%> (-1%)
lib/private/DB/MigrationService.php	85.29% <0%> (-5.15%)	53% <0%> (ø)
apps/files_external/lib/Lib/Storage/SMB.php	47.94% <0%> (-4.5%)	0% <0%> (ø)
...es_sharing/lib/Controller/Share20OcsController.php	87.5% <0%> (-0.07%)	211% <0%> (-2%)
...aring/appinfo/Migrations/Version20170804201125.php	0% <0%> (ø)	2% <0%> (ø)	⬇️
lib/private/Files/View.php	84.6% <0%> (+0.25%)	398% <0%> (-3%)	⬇️
lib/private/DB/QueryBuilder/QueryBuilder.php	91.34% <0%> (+0.48%)	68% <0%> (ø)	⬇️
lib/private/DB/Connection.php	67.64% <0%> (+0.73%)	49% <0%> (ø)	⬇️
... and 14 more

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #35612 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master   #35612      +/-   ##
============================================
+ Coverage     65.77%   65.77%   +<.01%     
  Complexity    18776    18776              
============================================
  Files          1222     1222              
  Lines         70871    70871              
  Branches       1289     1289              
============================================
+ Hits          46615    46616       +1     
+ Misses        23878    23877       -1     
  Partials        378      378

Flag	Coverage Δ	Complexity Δ
#javascript	53.7% <ø> (ø)	0 <ø> (ø)	⬇️
#phpunit	67.15% <100%> (ø)	18776 <0> (ø)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
lib/private/legacy/hook.php	79.41% <ø> (+2.26%)	17 <0> (ø)	⬇️
lib/private/Preview.php	80.16% <100%> (+0.04%)	178 <0> (ø)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a0f0e3d...2c58cc1. Read the comment docs.

[micbar]

Please backport.

[phil-davis]

Backport stable10 #35708