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Combining operators

Covering index optimization


Table: R(a, b, c, d, e, f, g)

Index: abc_idx(a, b, c)

Query:
    select b, c
    from R 
    where a = 1 and g < 3

Execution plan


Project(
    SelectScan(
        GetTableRow(
            R,
            SelectIndex(abc_idx, a = 1)),
        g < 3)
    [b, c])

Index: Index key -> row id
SelectIndex: Yields row ids
GetTableRow: Row id -> Row of table. Expensive! Lots of random access

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