Details
Critical - P2 Description
Here's a simple repro script, inspired by jstests/core/index_bounds_pipe.js:
(function() {
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"use strict";
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const coll = db.coll;
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coll.drop();
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assert.commandWorked(coll.insert({_id: "a"}));
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assert.commandWorked(coll.insert({_id: "b"}));
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assert.commandWorked(coll.insert({_id: "foo"}));
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// Run a query which results in an auto-parameterized index scan plan being added to the SBE plan
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// cache.
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assert.eq(coll.find({_id: /^a/}).itcount(), 1);
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// This query incorrectly reuses the cached plan, and as a result returns 3 results instead of 2.
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assert.eq(coll.find({_id: /^a|b/}).itcount(), 2);
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}());
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Note this this only triggers the problem if you also include the changes for SERVER-64315, since this repro depends on the caching of single solution plans.
I believe the problem is similar to SERVER-64776 – namely, the bounds tightness of the regex predicate is not correctly incorporated into the plan cache key. The first regex, /^a/, has exact bounds tightness, and therefore the predicate is "trimmed" and not included as an explicit filter in the execution plan. In contrast, /^a|b/ has inexact bounds and the regex must be reapplied to each index key. However, this query reuses a plan that has no filter stage. Consequently, the predicate does not get reapplied and the query returns extra results.
Attachments
Issue Links
- is depended on by
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SERVER-64315 Re-enable caching of single solution plans
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- Closed
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- is related to
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- Backlog
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SERVER-33511 Same Query Shape with different regex can give suboptimal index selection
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- Closed
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- Closed
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