# `Electric.Shapes.Filter.Indexes.EqualityIndex`
[🔗](https://github.com/electric-sql/electric/tree/%40core/sync-service%401.6.2/packages/sync-service/lib/electric/shapes/filter/indexes/equality_index.ex#L1)

Efficiently finds shapes that are affected by a change when the shape's where clause has `field = const` in it.

Data is stored in the Filter's eq_index_table ETS table with keys of the form:
`{condition_id, field, value}` -> `{type, next_condition_id}`

The type is stored to know how to parse values from records.
The next_condition_id points to a WhereCondition for the remaining conditions
of the where clause.

Additionally, the field type is cached at:
`{:type, condition_id, field}` -> type
This enables O(1) type lookup for parsing record values.

# `add_shape`

# `affected_shapes`

# `all_shape_ids`

# `remove_shape`

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*Consult [api-reference.md](api-reference.md) for complete listing*