[SERVER-15279] Disable hash-based index intersection (AND_HASH) by default Created: 16/Sep/14 Updated: 28/Dec/17 Resolved: 17/Sep/14 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Querying |
| Affects Version/s: | None |
| Fix Version/s: | 2.6.5, 2.7.7 |
| Type: | Task | Priority: | Major - P3 |
| Reporter: | David Storch | Assignee: | David Storch |
| Resolution: | Done | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Case: | (copied to CRM) | ||||||||||||||||||||
| Description |
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Performance testing has suggested that hash-based index intersection, implemented by the AND_HASH query execution stage, does not offer a significant performance advantage for test workloads. This is due in part to SERVER-12923, which describes how query optimization can suffer for plans that are not fully pipelined. Based on the results of this testing, we should disable hash-based intersection by default. It will be possible to re-enable AND_HASH at run time via:
Sort-based intersection will be on by default and will not be affected by this change. |
| Comments |
| Comment by Githook User [ 17/Sep/14 ] |
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Author: {u'username': u'dstorch', u'name': u'David Storch', u'email': u'david.storch@10gen.com'}Message: (cherry picked from commit 5e2b3c29b438f936eeb0a675e70e0131ab4c145a) Conflicts: |
| Comment by Githook User [ 17/Sep/14 ] |
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Author: {u'username': u'dstorch', u'name': u'David Storch', u'email': u'david.storch@10gen.com'}Message: |