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HPCC-33022 Fix pathological dali load time #19350

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jakesmith
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@jakesmith jakesmith commented Dec 11, 2024

JPTree (used by Dali SDS) could perform horrendously slowly when dealing with a large list of child nodes sharing a common prefix. This was due to how the hashing function was used (no seed number provided). With many entries having the same prefix, it caused a high number of hash collisions, resulting in excessive scanning when adding new members.
This particularly affected the /GeneratedDlls section of Dali. After fixing the issue, the time to load this section dropped from over 4700 seconds to 17 seconds.

Also add a 'loadxml' utility to daliadmin, that loads and times loading an xml file, and traces the amount of memory it consumes.

Type of change:

  • This change is a bug fix (non-breaking change which fixes an issue).
  • This change is a new feature (non-breaking change which adds functionality).
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  • This change fixes warnings (the fix does not alter the functionality or the generated code)
  • This change is a breaking change (fix or feature that will cause existing behavior to change).
  • This change alters the query API (existing queries will have to be recompiled)

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  • My code follows the code style of this project.
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Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-33022

Jirabot Action Result:
Assigning user: [email protected]
Workflow Transition To: Merge Pending
Updated PR

@jakesmith jakesmith requested a review from ghalliday December 11, 2024 10:34
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@jakesmith one question, otherwise approved

@@ -31,9 +31,6 @@
#if defined(__clang__) || defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wformat-nonliteral"

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was this deletion on purpose?

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yep, I'll reverse

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@ghalliday - I've reverted that change (squashed in)

JPTree (used by Dali SDS) could perform horrendously slowly when
dealing with a large list of child nodes sharing a common
prefix. This was due to how the hashing function was used
(no seed number provided). With many entries having the same
prefix, it caused a high number of hash collisions, resulting
in excessive scanning when adding new members.
This particularly affected the /GeneratedDlls section of Dali.
After fixing the issue, the time to load this section dropped
from over 4700 seconds to 17 seconds.

Also add a 'loadxml' utility to daliadmin, that loads and
times loading an xml file, and traces the amount of memory it
consumes.

Signed-off-by: Jake Smith <[email protected]>
@jakesmith jakesmith force-pushed the HPCC-33022-pathological-jptree-ht-perf branch from b9c6195 to bb1a9e1 Compare December 11, 2024 16:26
@ghalliday ghalliday merged commit 959f55e into hpcc-systems:candidate-9.2.x Dec 11, 2024
49 of 50 checks passed
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Jirabot Action Result:
Added fix version: 9.2.146
Added fix version: 9.4.120
Added fix version: 9.6.72
Added fix version: 9.8.46
Workflow Transition: 'Resolve issue'

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2 participants