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Merge pull request #1228 from geoffmacd/window-functions
Implements built-in window functions
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,145 @@ | ||
| import Foundation | ||
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| // see https://www.sqlite.org/windowfunctions.html#builtins | ||
| private enum WindowFunction: String { | ||
| // swiftlint:disable identifier_name | ||
| case ntile | ||
| case row_number | ||
| case rank | ||
| case dense_rank | ||
| case percent_rank | ||
| case cume_dist | ||
| case lag | ||
| case lead | ||
| case first_value | ||
| case last_value | ||
| case nth_value | ||
| // swiftlint:enable identifier_name | ||
|
|
||
| func wrap<T>(_ value: Int? = nil) -> Expression<T> { | ||
| if let value { | ||
| return self.rawValue.wrap(Expression(value: value)) | ||
| } | ||
| return Expression(literal: "\(rawValue)()") | ||
| } | ||
|
|
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| func over<T>(value: Int? = nil, _ orderBy: Expressible) -> Expression<T> { | ||
| return Expression<T>(" ".join([ | ||
| self.wrap(value), | ||
| Expression<T>("OVER (ORDER BY \(orderBy.expression.template))", orderBy.expression.bindings) | ||
| ]).expression) | ||
| } | ||
|
|
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| func over<T>(valueExpr: Expressible, _ orderBy: Expressible) -> Expression<T> { | ||
| return Expression<T>(" ".join([ | ||
| self.rawValue.wrap(valueExpr), | ||
| Expression<T>("OVER (ORDER BY \(orderBy.expression.template))", orderBy.expression.bindings) | ||
| ]).expression) | ||
| } | ||
| } | ||
|
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| extension ExpressionType where UnderlyingType: Value { | ||
| /// Builds a copy of the expression with `lag(self, offset, default) OVER (ORDER BY {orderBy})` window function | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `lag(self, offset, default) OVER (ORDER BY {orderBy})` window function | ||
| public func lag(offset: Int = 0, default: Expressible? = nil, _ orderBy: Expressible) -> Expression<UnderlyingType> { | ||
| if let defaultExpression = `default` { | ||
| return Expression( | ||
| "lag(\(template), \(offset), \(defaultExpression.asSQL())) OVER (ORDER BY \(orderBy.expression.template))", | ||
| bindings + orderBy.expression.bindings | ||
| ) | ||
|
|
||
| } | ||
| return Expression("lag(\(template), \(offset)) OVER (ORDER BY \(orderBy.expression.template))", bindings + orderBy.expression.bindings) | ||
| } | ||
|
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| /// Builds a copy of the expression with `lead(self, offset, default) OVER (ORDER BY {orderBy})` window function | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `lead(self, offset, default) OVER (ORDER BY {orderBy})` window function | ||
| public func lead(offset: Int = 0, default: Expressible? = nil, _ orderBy: Expressible) -> Expression<UnderlyingType> { | ||
| if let defaultExpression = `default` { | ||
| return Expression( | ||
| "lead(\(template), \(offset), \(defaultExpression.asSQL())) OVER (ORDER BY \(orderBy.expression.template))", | ||
| bindings + orderBy.expression.bindings) | ||
|
|
||
| } | ||
| return Expression("lead(\(template), \(offset)) OVER (ORDER BY \(orderBy.expression.template))", bindings + orderBy.expression.bindings) | ||
| } | ||
|
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| /// Builds a copy of the expression with `first_value(self) OVER (ORDER BY {orderBy})` window function | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `first_value(self) OVER (ORDER BY {orderBy})` window function | ||
| public func firstValue(_ orderBy: Expressible) -> Expression<UnderlyingType> { | ||
| WindowFunction.first_value.over(valueExpr: self, orderBy) | ||
| } | ||
|
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| /// Builds a copy of the expression with `last_value(self) OVER (ORDER BY {orderBy})` window function | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `last_value(self) OVER (ORDER BY {orderBy})` window function | ||
| public func lastValue(_ orderBy: Expressible) -> Expression<UnderlyingType> { | ||
| WindowFunction.last_value.over(valueExpr: self, orderBy) | ||
| } | ||
|
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| /// Builds a copy of the expression with `nth_value(self) OVER (ORDER BY {orderBy})` window function | ||
| /// | ||
| /// - Parameter index: Row N of the window frame to return | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `nth_value(self) OVER (ORDER BY {orderBy})` window function | ||
| public func value(_ index: Int, _ orderBy: Expressible) -> Expression<UnderlyingType> { | ||
| Expression("nth_value(\(template), \(index)) OVER (ORDER BY \(orderBy.expression.template))", bindings + orderBy.expression.bindings) | ||
| } | ||
| } | ||
|
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| /// Builds an expression representing `ntile(size) OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `ntile(size) OVER (ORDER BY {orderBy})` | ||
| public func ntile(_ size: Int, _ orderBy: Expressible) -> Expression<Int> { | ||
| // Expression.ntile(size, orderBy) | ||
|
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| WindowFunction.ntile.over(value: size, orderBy) | ||
| } | ||
|
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| /// Builds an expression representing `row_count() OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `row_count() OVER (ORDER BY {orderBy})` | ||
| public func rowNumber(_ orderBy: Expressible) -> Expression<Int> { | ||
| WindowFunction.row_number.over(orderBy) | ||
| } | ||
|
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| /// Builds an expression representing `rank() OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `rank() OVER (ORDER BY {orderBy})` | ||
| public func rank(_ orderBy: Expressible) -> Expression<Int> { | ||
| WindowFunction.rank.over(orderBy) | ||
| } | ||
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| /// Builds an expression representing `dense_rank() OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `dense_rank() OVER ('over')` | ||
| public func denseRank(_ orderBy: Expressible) -> Expression<Int> { | ||
| WindowFunction.dense_rank.over(orderBy) | ||
| } | ||
|
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| /// Builds an expression representing `percent_rank() OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `percent_rank() OVER (ORDER BY {orderBy})` | ||
| public func percentRank(_ orderBy: Expressible) -> Expression<Double> { | ||
| WindowFunction.percent_rank.over(orderBy) | ||
| } | ||
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| /// Builds an expression representing `cume_dist() OVER (ORDER BY {orderBy})` | ||
| /// | ||
| /// - Parameter orderBy: Expression to evaluate window order | ||
| /// - Returns: An expression returning `cume_dist() OVER (ORDER BY {orderBy})` | ||
| public func cumeDist(_ orderBy: Expressible) -> Expression<Double> { | ||
| WindowFunction.cume_dist.over(orderBy) | ||
| } |
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