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fix(core): fix rare index reader memory on partition drop#6087

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ideoma merged 2 commits intomasterfrom
jh_index_leak_after_deleted_partition
Sep 1, 2025
Merged

fix(core): fix rare index reader memory on partition drop#6087
ideoma merged 2 commits intomasterfrom
jh_index_leak_after_deleted_partition

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@jerrinot
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@jerrinot jerrinot commented Aug 30, 2025 •
edited by ideoma
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A partition removal followed by a schema change could cause a memory and file descriptor leak
It's fixing a FD and memory leak found by a fuzz test.

WIP.
Scenario:

  1. Partition gets deleted -> stale bitmap indexes left in bitmapIndexes list beyond a valid range (at position not references by any column)
  2. Eventually, a table schema change triggers createNewColumnList()
  3. createNewColumnList() creates a new bitmapIndexes list but only copies indexes from the old list within a valid range
  4. The stale indexes beyond the range are not included in the new bitmap index list
  5. When old arrays are replaced with new ones, those stale indexes are orphaned - they remain open but unreachable
  6. FD leak - the file descriptors for those bitmap indexes are never closed

Note:
I am not quite sure if Misc.free(bitmapIndexes.get(i)); is needed. I added it only because of the Misc.free(columns.get(i)); above. but it appears to me that both columns and indexes should be closed above at closePartitionResource():

if (partitionSize > -1) {
    closePartitionResources(partitionIndex, offset);
    openPartitionCount--;
}
int baseIndex = getPrimaryColumnIndex(columnBase, 0);
int newBaseIndex = getPrimaryColumnIndex(getColumnBase(partitionIndex + 1), 0);
for (int i = baseIndex, n = newBaseIndex - 1; i < n; i++) {
    // Close columns before deleting the objects.
    // FD leak caught by failing fuzz tests.
    Misc.free(columns.get(i)); <--- pre-existing line. is it needed? why? 
    Misc.free(bitmapIndexes.get(i)); <-- is this needed? why? 
}

but the partitionSize > -1 guard prevents the resources to be closed?

@jerrinot
fix(core): index reader memory leak fix
d2b702b 
a partition removal followed by a schema change could cause a memory and file descriptor leak
@jerrinot jerrinot added Bug Incorrect or unexpected behavior Core Related to storage, data type, etc. labels Aug 30, 2025
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@glasstiger
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glasstiger commented Aug 31, 2025

[PR Coverage check]

😍 pass : 3 / 3 (100.00%)

file detail

path covered line new line coverage
🔵 io/questdb/cairo/TableReader.java 3 3 100.00%

ideoma
ideoma reviewed Sep 1, 2025
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Looks good, what about tests?

@ideoma ideoma changed the title fix(core): index reader memory leak fix fix(core): fix rare index reader memory on partition drop Sep 1, 2025
@ideoma ideoma merged commit 39f84f2 into master Sep 1, 2025
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@ideoma ideoma deleted the jh_index_leak_after_deleted_partition branch September 1, 2025 08:17
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@jerrinot @glasstiger @ideoma @bluestreak01