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Add cursor type for more safety. #726

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Add cursor type for more safety. #726

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586a993
Add cursor type for more safety.
nickmshelley May 5, 2017
79f8095
Change fatalError to throw.
nickmshelley Sep 20, 2017
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8 changes: 8 additions & 0 deletions Sources/SQLite/Core/Statement.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,14 @@ public final class Statement {

}

extension Statement {

func rowCursorNext() throws -> [Binding?]? {
return try step() ? Array(row) : nil
}

}

extension Statement : Sequence {

public func makeIterator() -> Statement {
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111 changes: 71 additions & 40 deletions Sources/SQLite/Typed/Query.swift
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Expand Up @@ -894,58 +894,89 @@ public struct Delete : ExpressionType {

}

public struct RowCursor {
let statement: Statement
let columnNames: [String: Int]

public func next() throws -> Row? {
return try statement.rowCursorNext().flatMap { Row(columnNames, $0) }
}

public func map<T>(_ transform: (Row) throws -> T) throws -> [T] {
var elements = [T]()
while true {
if let row = try next() {
elements.append(try transform(row))
} else {
break
}
}

return elements
}
}

extension Connection {

public func prepareCursor(_ query: QueryType) throws -> RowCursor {
let expression = query.expression
let statement = try prepare(expression.template, expression.bindings)
return RowCursor(statement: statement, columnNames: try columnNamesForQuery(query))
}

public func prepare(_ query: QueryType) throws -> AnySequence<Row> {
let expression = query.expression
let statement = try prepare(expression.template, expression.bindings)

let columnNames: [String: Int] = try {
var (columnNames, idx) = ([String: Int](), 0)
column: for each in query.clauses.select.columns {
var names = each.expression.template.characters.split { $0 == "." }.map(String.init)
let column = names.removeLast()
let namespace = names.joined(separator: ".")

func expandGlob(_ namespace: Bool) -> ((QueryType) throws -> Void) {
return { (query: QueryType) throws -> (Void) in
var q = type(of: query).init(query.clauses.from.name, database: query.clauses.from.database)
q.clauses.select = query.clauses.select
let e = q.expression
var names = try self.prepare(e.template, e.bindings).columnNames.map { $0.quote() }
if namespace { names = names.map { "\(query.tableName().expression.template).\($0)" } }
for name in names { columnNames[name] = idx; idx += 1 }
}
}
let columnNames = try columnNamesForQuery(query)

if column == "*" {
var select = query
select.clauses.select = (false, [Expression<Void>(literal: "*") as Expressible])
let queries = [select] + query.clauses.join.map { $0.query }
if !namespace.isEmpty {
for q in queries {
if q.tableName().expression.template == namespace {
try expandGlob(true)(q)
continue column
}
return AnySequence {
AnyIterator { statement.next().map { Row(columnNames, $0) } }
}
}

private func columnNamesForQuery(_ query: QueryType) throws -> [String: Int] {
var (columnNames, idx) = ([String: Int](), 0)
column: for each in query.clauses.select.columns {
var names = each.expression.template.characters.split { $0 == "." }.map(String.init)
let column = names.removeLast()
let namespace = names.joined(separator: ".")

func expandGlob(_ namespace: Bool) -> ((QueryType) throws -> Void) {
return { (query: QueryType) throws -> (Void) in
var q = type(of: query).init(query.clauses.from.name, database: query.clauses.from.database)
q.clauses.select = query.clauses.select
let e = q.expression
var names = try self.prepare(e.template, e.bindings).columnNames.map { $0.quote() }
if namespace { names = names.map { "\(query.tableName().expression.template).\($0)" } }
for name in names { columnNames[name] = idx; idx += 1 }
}
}

if column == "*" {
var select = query
select.clauses.select = (false, [Expression<Void>(literal: "*") as Expressible])
let queries = [select] + query.clauses.join.map { $0.query }
if !namespace.isEmpty {
for q in queries {
if q.tableName().expression.template == namespace {
try expandGlob(true)(q)
continue column
}
throw QueryError.noSuchTable(name: namespace)
}
for q in queries {
try expandGlob(query.clauses.join.count > 0)(q)
}
continue
fatalError("no such table: \(namespace)")
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this should probably be QueryError.noSuchTable?

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Good call. Sorry I took so long to make this simple change.

}

columnNames[each.expression.template] = idx
idx += 1
for q in queries {
try expandGlob(query.clauses.join.count > 0)(q)
}
continue
}
return columnNames
}()

return AnySequence {
AnyIterator { statement.next().map { Row(columnNames, $0) } }

columnNames[each.expression.template] = idx
idx += 1
}
return columnNames
}

public func scalar<V : Value>(_ query: ScalarQuery<V>) throws -> V {
Expand All @@ -971,7 +1002,7 @@ extension Connection {
}

public func pluck(_ query: QueryType) throws -> Row? {
return try prepare(query.limit(1, query.clauses.limit?.offset)).makeIterator().next()
return try prepareCursor(query.limit(1, query.clauses.limit?.offset)).next()
}

/// Runs an `Insert` query.
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10 changes: 10 additions & 0 deletions Tests/SQLiteTests/QueryTests.swift
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Expand Up @@ -347,6 +347,16 @@ class QueryIntegrationTests : SQLiteTestCase {
_ = user[users[managerId]]
}
}

func test_prepareCursor() {
let names = ["a", "b", "c"]
try! InsertUsers(names)

let emailColumn = Expression<String>("email")
let emails = try! db.prepareCursor(users).map { $0[emailColumn] }

XCTAssertEqual(names.map({ "\($0)@example.com" }), emails.sorted())
}

func test_select_optional() {
for _ in try! db.prepare(users) {
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