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zeus
2025-01-22 16:22:33 +08:00
parent 09b9cec8ec
commit 738c373a77
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iOS-SwiftUI-Code/GRDB.swift-6.29.3/GRDB/QueryInterface/Schema/VirtualTableModule.swift
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/// The protocol for SQLite virtual table modules.
///
/// The protocol can define a DSL for the
/// ``Database/create(virtualTable:ifNotExists:using:_:)`` `Database` method:
///
/// ```swift
/// let module = ...
/// try db.create(virtualTable: "item", using: module) { t in
/// ...
/// }
/// ```
///
/// GRDB ships with three concrete classes that implement this protocol:
/// ``FTS3``, ``FTS4`` and `FTS5`.
///
/// ## Topics
///
/// ### Configuration Virtual Table Creation
///
/// - ``VirtualTableConfiguration``
public protocol VirtualTableModule {
/// The type of the argument in the
/// ``Database/create(virtualTable:ifNotExists:using:_:)`` closure.
///
/// For example:
///
/// ```swift
/// try db.create(virtualTable: "item", using: module) { t in
/// // t is TableDefinition
/// }
/// ```
associatedtype TableDefinition
/// The name of the module.
var moduleName: String { get }
/// Returns a table definition that is passed as the argument in the
/// ``Database/create(virtualTable:ifNotExists:using:_:)`` closure.
///
/// For example:
///
/// ```swift
/// try db.create(virtualTable: "item", using: module) { t in
/// // t is the result of makeTableDefinition(configuration:)
/// }
/// ```
func makeTableDefinition(configuration: VirtualTableConfiguration) -> TableDefinition
/// Returns the module arguments for the `CREATE VIRTUAL TABLE` query.
func moduleArguments(for definition: TableDefinition, in db: Database) throws -> [String]
/// Execute any relevant database statement after the virtual table has
/// been created.
func database(_ db: Database, didCreate tableName: String, using definition: TableDefinition) throws
}
public struct VirtualTableConfiguration {
/// If true, existing objects must not be replaced, or generate any error
/// (even if they do not match the objects that would be created otherwise.)
var ifNotExists: Bool
}
extension Database {
// MARK: - Database Schema
/// Creates a virtual database table.
///
/// For example:
///
/// ```swift
/// // CREATE VIRTUAL TABLE vocabulary USING spellfix1
/// try db.create(virtualTable: "vocabulary", using: "spellfix1")
/// ```
///
/// Related SQLite documentation: <https://www.sqlite.org/lang_createtable.html>
///
/// - parameters:
/// - name: The table name.
/// - ifNotExists: If false (the default), an error is thrown if the
/// table already exists. Otherwise, the table is created unless it
/// already exists.
/// - module: The name of an SQLite virtual table module.
/// - throws: A ``DatabaseError`` whenever an SQLite error occurs.
public func create(virtualTable name: String, ifNotExists: Bool = false, using module: String) throws {
var chunks: [String] = []
chunks.append("CREATE VIRTUAL TABLE")
if ifNotExists {
chunks.append("IF NOT EXISTS")
}
chunks.append(name.quotedDatabaseIdentifier)
chunks.append("USING")
chunks.append(module)
let sql = chunks.joined(separator: " ")
try execute(sql: sql)
}
/// Creates a virtual database table.
///
/// The type of the argument of the `body` function depends on the type of
/// the `module` argument: refer to this module's documentation.
///
/// You can use this method to create full-text virtual tables:
///
/// ```swift
/// try db.create(virtualTable: "book", using: FTS4()) { t in
/// t.column("title")
/// t.column("author")
/// t.column("body")
/// }
/// ```
///
/// Related SQLite documentation: <https://www.sqlite.org/lang_createtable.html>
///
/// - parameters:
/// - name: The table name.
/// - ifNotExists: If false (the default), an error is thrown if the
/// table already exists. Otherwise, the table is created unless it
/// already exists.
/// - module: a virtual module.
/// - body: An optional closure that defines the virtual table.
/// - throws: A ``DatabaseError`` whenever an SQLite error occurs.
public func create<Module: VirtualTableModule>(
virtualTable tableName: String,
ifNotExists: Bool = false,
using module: Module,
_ body: ((Module.TableDefinition) throws -> Void)? = nil)
throws
{
// Define virtual table
let configuration = VirtualTableConfiguration(ifNotExists: ifNotExists)
let definition = module.makeTableDefinition(configuration: configuration)
if let body {
try body(definition)
}
// Create virtual table
var chunks: [String] = []
chunks.append("CREATE VIRTUAL TABLE")
if ifNotExists {
chunks.append("IF NOT EXISTS")
}
chunks.append(tableName.quotedDatabaseIdentifier)
chunks.append("USING")
let arguments = try module.moduleArguments(for: definition, in: self)
if arguments.isEmpty {
chunks.append(module.moduleName)
} else {
chunks.append(module.moduleName + "(" + arguments.joined(separator: ", ") + ")")
}
let sql = chunks.joined(separator: " ")
try inSavepoint {
try execute(sql: sql)
try module.database(self, didCreate: tableName, using: definition)
return .commit
}
}
}