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Bug Fix: Handle multi-part lists properly in ReadPostingList #4574

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merged 11 commits into from Jan 22, 2020

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@martinmr martinmr commented Jan 14, 2020

This PR changes ReadPostingList to skip over the parts of a multi-part list so that they are not accessed the next time ReadPostingList is called. A multi-part posting list should only be accessed via the main key. Accessing the posting list via one of the other keys was causing issues during rollup and adding spurious keys to the database, which eventually caused reads to return nil in the Jepsen uid-set test.


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martinmr added 3 commits Jan 14, 2020
If a key has a startUid > 0 it should not be read by ReadPostingList.
Instead, when the main key is accessed, the iterator should be advanced
so that these keys are skipped over.
@martinmr martinmr changed the title Skip over multi-part list keys. Handle multi-part lists properly in ReadPostingList Jan 14, 2020
@martinmr martinmr marked this pull request as ready for review Jan 15, 2020
@martinmr martinmr requested a review from manishrjain as a code owner Jan 15, 2020
@martinmr martinmr requested a review from Jan 15, 2020
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@manishrjain manishrjain left a comment

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @manishrjain and @martinmr)


posting/list.go, line 491 at r1 (raw file):

func (l *List) Iterate(readTs uint64, afterUid uint64, f func(obj *pb.Posting) error) error {
	if l == nil {
		return nil

I'd create an error called errorNilList, and return it for all the funcs.


posting/mvcc.go, line 151 at r2 (raw file):

		// Trying to read a single part of a multi part list. This type of list
		// should be read once using the canonical list (with startUid equal to zero).
		return nil, nil

No nil error here. Should have a pre-defined error.

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@martinmr martinmr left a comment

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @manishrjain)


posting/list.go, line 491 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

I'd create an error called errorNilList, and return it for all the funcs.

Removed the special nil handling in favor of not returning nil lists in ReadPostingList


posting/mvcc.go, line 151 at r2 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

No nil error here. Should have a pre-defined error.

Done.

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@parasssh parasssh left a comment

Reviewable status: 0 of 2 files reviewed, 3 unresolved discussions (waiting on @manishrjain and @martinmr)

a discussion (no related file):
:lgtm:


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@manishrjain manishrjain left a comment

:lgtm: Hope you ran Jepsen!

Reviewed 2 of 2 files at r3.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @manishrjain and @martinmr)


posting/list.go, line 1136 at r3 (raw file):

func (l *List) Facets(readTs uint64, param *pb.FacetParams, langs []string,
	listType bool) ([]*pb.Facets, error) {
	l.RLock()

revert all changes here.


posting/mvcc.go, line 150 at r3 (raw file):

	if err != nil {
		return nil, errors.Wrapf(err, "while reading posting list with key [%v]", key)
	}

Comment here that we used to have a bug here, as caught by . This PR fixes that.

@manishrjain manishrjain changed the title Handle multi-part lists properly in ReadPostingList Bug Fix: Handle multi-part lists properly in ReadPostingList Jan 22, 2020
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@martinmr martinmr left a comment

Reviewable status: 0 of 2 files reviewed, 4 unresolved discussions (waiting on @manishrjain and @martinmr)


posting/list.go, line 1136 at r3 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

revert all changes here.

Done.


posting/mvcc.go, line 150 at r3 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Comment here that we used to have a bug here, as caught by . This PR fixes that.

Done.

@martinmr martinmr merged commit 9eb7c0a into master Jan 22, 2020
7 of 8 checks passed
@martinmr martinmr deleted the martinmr/jepsen-fix branch Jan 22, 2020
danielmai pushed a commit that referenced this issue Feb 6, 2020
This PR changes ReadPostingList to skip over the parts of a multi-part list so that
they are not accessed the next time ReadPostingList is called. A multi-part posting
list should only be accessed via the main key. Accessing the posting list via one of
the other keys was causing issues during rollup and adding spurious keys to the
database, which eventually caused reads to return nil in the Jepsen uid-set test.
danielmai added a commit that referenced this issue Feb 6, 2020
* Revert "Disable splits in release 1.2 (#4672)"

This reverts commit 1846c68.

* Bug Fix: Handle multi-part lists properly in ReadPostingList (#4574)

This PR changes ReadPostingList to skip over the parts of a multi-part list so that
they are not accessed the next time ReadPostingList is called. A multi-part posting
list should only be accessed via the main key. Accessing the posting list via one of
the other keys was causing issues during rollup and adding spurious keys to the
database, which eventually caused reads to return nil in the Jepsen uid-set test.

* Add checks to verify expected number of list splits in list_test.go (#4609)

(cherry picked from commit 9ca59f8)

Co-authored-by: Martin Martinez Rivera <martinmr@users.noreply.github.com>
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3 participants