Loading...

XML

Word

Printable

JSON

Sometimes, part of the predicate can be pushed down to the IXSCAN stage filter and minimise or even avoid fetching.

Predicate: AND [a=1, b=1]

Sort: c_1

Index: (c_1_a_1)

Resulting query

FETCH
    filter: AND [a=1, b=1]
    IXSCAN:
        pattern: (c_1_a_1)

Optimal query:

FETCH
    filter: b=1
    IXSCAN:
        filter: a=1
        pattern: (c_1_a_1)

causes

SERVER-107527 Incorrect predicates push down to IndexScan

duplicates

SERVER-13197 Tighten index bounds and allow compound index to be chosen when predicate on leading field is not provided

is duplicated by

SERVER-122725 Investigate eliding FetchNode if the predicate in root is covered.

is related to

SERVER-122796 Incorrect results for $elemMatch-$not when index is hinted

SERVER-122819 Investigate ways to improve PBT effectiveness in patches

SERVER-91404 Randomize property tester in waterfall

related to

SERVER-12769 Queries that scan an entire index to provide a sort should be covered when possible

(1 is related to, 1 related to)