Class: UnnestedInFilters::Rewriter::IndexCoverage

Inherits:
Object
  • Object
show all
Defined in:
lib/unnested_in_filters/rewriter.rb

Overview

A naive query planner implementation. Checks if a database-level index can be utilized by given filtering and ordering predicates.

Supported index conditions:

- All columns queried are present in the index or partial predicate
- Unqueried index columns are at the end of the index
- Partial indices if the partial index predicate contains only one column.
- Only the `=` operator present in partial index predicate.

Examples:

Queried | Index | Supported? (col_1, col_2) | (col_1, col_2) | Y (col_1) | (col_1, col_2) | Y (col_2) | (col_1, col_2) | N (col_1, col_3) | (col_1, col_2, col_3) | N (col_1, col_2) | (col_1) where col_2 = “1” | Y (col_1, col_2) | (col_1) where col_2 <= 1 | N (col_1, col_2) | (col_1) where col_2 IS NULL | N (col_1, col_2) | (col_1) where col_2 = “1” AND COL_1 = “2” | N

Constant Summary collapse

PARTIAL_INDEX_REGEX = 
/(?<!\s)(?>\(*(?<column_name>\b\w+)\s*=\s*(?<column_value>\w+)\)*)(?!\s)/

Instance Method Summary collapse

Constructor Details

#initialize(index, where_hash, order_attributes) ⇒ IndexCoverage

Returns a new instance of IndexCoverage.



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# File 'lib/unnested_in_filters/rewriter.rb', line 101

def initialize(index, where_hash, order_attributes)
  @index = index
  @where_hash = where_hash
  @order_attributes = order_attributes
end

Instance Method Details

#covers? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/unnested_in_filters/rewriter.rb', line 107

def covers?
  filter_attributes_covered?            &&
    unused_columns_at_end_of_index?     &&
    can_be_used_for_sorting?
end