56b1efc6f1
This is a potential fix for some of the crash reports that have been streaming in. They all seem to be crashing within ndb_close_txn. I suspect this means that the transactions are trying to get closed when ndb is already closed. Closing Ndb will close the transactions automatically, so it looks like we might be trying to close twice.
123 lines
3.8 KiB
Swift
123 lines
3.8 KiB
Swift
//
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// NdbTx.swift
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// damus
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//
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// Created by William Casarin on 2023-08-30.
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//
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import Foundation
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#if TXNDEBUG
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fileprivate var txn_count: Int = 0
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#endif
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// Would use struct and ~Copyable but generics aren't supported well
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class NdbTxn<T> {
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var txn: ndb_txn
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private var val: T!
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var moved: Bool
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var inherited: Bool
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var ndb: Ndb
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init?(ndb: Ndb, with: (NdbTxn<T>) -> T = { _ in () }) {
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guard !ndb.closed else { return nil }
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self.ndb = ndb
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#if TXNDEBUG
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txn_count += 1
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print("opening transaction \(txn_count)")
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#endif
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if let active_txn = Thread.current.threadDictionary["ndb_txn"] as? ndb_txn {
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// some parent thread is active, use that instead
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self.txn = active_txn
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self.inherited = true
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} else {
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self.txn = ndb_txn()
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let ok = ndb_begin_query(ndb.ndb.ndb, &self.txn) != 0
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if !ok {
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return nil
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}
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Thread.current.threadDictionary["ndb_txn"] = self.txn
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self.inherited = false
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}
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self.moved = false
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self.val = with(self)
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}
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private init(ndb: Ndb, txn: ndb_txn, val: T) {
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self.txn = txn
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self.val = val
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self.moved = false
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self.inherited = false
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self.ndb = ndb
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}
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/// Only access temporarily! Do not store database references for longterm use. If it's a primitive type you
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/// can retrieve this value with `.value`
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var unsafeUnownedValue: T {
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precondition(!moved)
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return val
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}
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deinit {
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if moved || inherited || ndb.closed {
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return
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}
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#if TXNDEBUG
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txn_count -= 1;
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print("closing transaction \(txn_count)")
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#endif
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ndb_end_query(&self.txn)
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Thread.current.threadDictionary.removeObject(forKey: "ndb_txn")
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}
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// functor
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func map<Y>(_ transform: (T) -> Y) -> NdbTxn<Y> {
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self.moved = true
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return .init(ndb: self.ndb, txn: self.txn, val: transform(val))
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}
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// comonad!?
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// useful for moving ownership of a transaction to another value
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func extend<Y>(_ with: (NdbTxn<T>) -> Y) -> NdbTxn<Y> {
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self.moved = true
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return .init(ndb: self.ndb, txn: self.txn, val: with(self))
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}
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}
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protocol OptionalType {
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associatedtype Wrapped
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var optional: Wrapped? { get }
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}
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extension Optional: OptionalType {
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typealias Wrapped = Wrapped
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var optional: Wrapped? {
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return self
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}
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}
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extension NdbTxn where T: OptionalType {
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func collect() -> NdbTxn<T.Wrapped>? {
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guard let unwrappedVal: T.Wrapped = val.optional else {
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return nil
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}
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self.moved = true
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return NdbTxn<T.Wrapped>(ndb: self.ndb, txn: self.txn, val: unwrappedVal)
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}
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}
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extension NdbTxn where T == Bool { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == Bool? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == Int { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == Int? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == Double { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == Double? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == UInt64 { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == UInt64? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == String { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == String? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == NoteId? { var value: T { return self.unsafeUnownedValue } }
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extension NdbTxn where T == NoteId { var value: T { return self.unsafeUnownedValue } }
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