oracle - When may it make sense to not have an index on a table and why? -
for oracle , being relative application tuning, when may make sense not have index on table , why?
there cost associated having index:
- it takes disk space
- it slows down updates (index needs updated well)
- it makes query planning more complex (slightly slower, more importantly increased potential bad decisions)
these costs supposed offset benefit of more efficient query processing (faster, fewer i/o).
if index not used enough justify cost, having index negative.
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