Update MongoDB $or queries to avoid SERVER-13732 bug#3476
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TylerBrock merged 1 commit intoparse-community:masterfrom Feb 4, 2017
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MongoDB has an unfixed bug in all supported versions 2.6-3.4 which results in suboptimal index usage for `$or` queries when the query has implicit `$and`s at the query root. When adding `_rperm` to `$or` queries, Parse accidentally creates queries which hit this bug. The fix in this commit applies the suggested workaround of putting the `_rperm` property inside all `$or` subdocuments, moving it from the top level and leaving `$or` as the only top-level operator. MongoDB Bug Link: https://jira.mongodb.org/browse/SERVER-13732
NotBobTheBuilder
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TylerBrock
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Feb 4, 2017
| return qobj; | ||
| }); | ||
| } else { | ||
| newQuery._rperm = { "$in" : [null, "*", ...acl]}; |
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The spacing between the closing } and the ] is odd here and should have a space as well as the above '$in' in the if block.
TylerBrock
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Feb 4, 2017
| //Can't be any existing '_rperm' query, we don't allow client queries on that, no need to $and | ||
| newQuery._rperm = { "$in" : [null, "*", ...acl]}; | ||
| if (newQuery.hasOwnProperty('$or')) { | ||
| newQuery.$or = newQuery.$or.map(function(qobj) { |
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It might be nice to add a comment here that provides a link to the MongoDB JIRA ticket and a note that we are intentionally distributing the _rperm predicate.
Contributor
|
Nice catch and workaround! Thanks for the contribution. |
NotBobTheBuilder
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Feb 24, 2017
In a prior commit, improvements were made to the addition of `_rperm` in the case of `$or` queries, to avoid MongoDB bug SERVER-13732. As the vast majority of $or queries previously hit this bug due to the presence of `_rperm` on most Parse queries), the present solution avoids the bug and improves query performance in most cases. However, it's still possible for clients to supply their own queries which hit that bug, such as those with `_created_at` or `_updated_at` filters, or their own properties from their data model. This commit makes the logic currently present for `_rperm` available to all top level filters that exist alongside an $or query, meaning SERVER-13732 should be avoided in all cases where keys at the top and inner levels do not have name clashes. - parse-community#3476 - https://jira.mongodb.org/browse/SERVER-13732
flovilmart
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Feb 26, 2017
In a prior commit, improvements were made to the addition of `_rperm` in the case of `$or` queries, to avoid MongoDB bug SERVER-13732. As the vast majority of $or queries previously hit this bug due to the presence of `_rperm` on most Parse queries), the present solution avoids the bug and improves query performance in most cases. However, it's still possible for clients to supply their own queries which hit that bug, such as those with `_created_at` or `_updated_at` filters, or their own properties from their data model. This commit makes the logic currently present for `_rperm` available to all top level filters that exist alongside an $or query, meaning SERVER-13732 should be avoided in all cases where keys at the top and inner levels do not have name clashes. - #3476 - https://jira.mongodb.org/browse/SERVER-13732
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MongoDB has an unfixed bug in all supported versions 2.6-3.4 which
results in suboptimal index usage for
$orqueries when the query hasimplicit
$ands at the query root.When adding
_rpermto$orqueries, Parse accidentally createsqueries which hit this bug.
The fix in this commit applies the suggested workaround of putting the
_rpermproperty inside all$orsubdocuments, moving it from the toplevel and leaving
$oras the only top-level operator.MongoDB Bug Link: https://jira.mongodb.org/browse/SERVER-13732