A letter to the internet, and lo, the entire English writing population.

[nephroth]

The Apostrophe's function is not plurality but possession.

Example:
"This database has ten indexes"
Is correct.

"This database has ten index's"
Is not correct.

"This indexes binary tree has 500 nodes"
Is not correct.

"This index's binary tree has 500 nodes"
Is correct.

"The knife's blade is embedded in your groin for misusing apostrophes"
Is correct.

I hope these examples have helped clear up the confusion you apparently have.