PostgreSql: TimeZoneInfo as DefaultTimeZone

no loading data from server

Author: alex-kulakov

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/DriverFactory.cs

@@ -13,7 +13,6 @@
 using Xtensive.Orm;
 using Xtensive.Sql.Info;
 using Xtensive.Sql.Drivers.PostgreSql.Resources;
-using System.Collections.Generic;
 
 namespace Xtensive.Sql.Drivers.PostgreSql
 {
@@ -67,9 +66,9 @@ protected override SqlDriver CreateDriver(string connectionString, SqlDriverConf
       else
         OpenConnectionFast(connection, configuration, false).GetAwaiter().GetResult();
       var version = GetVersion(configuration, connection);
-      var serverTimezones = GetServerTimeZones(connection, false).GetAwaiter().GetResult();
       var defaultSchema = GetDefaultSchema(connection);
-      return CreateDriverInstance(connectionString, version, defaultSchema, serverTimezones, connection.Timezone);
+      var defaultTimeZoneInfo = PostgreSqlHelper.GetTimeZoneInfoForServerTimeZone(connection.Timezone);
+      return CreateDriverInstance(connectionString, version, defaultSchema, defaultTimeZoneInfo);
     }
 
     /// <inheritdoc/>
@@ -87,9 +86,9 @@ protected override async Task<SqlDriver> CreateDriverAsync(
         else
           await OpenConnectionFast(connection, configuration, true, token).ConfigureAwait(false);
         var version = GetVersion(configuration, connection);
-        var serverTimezones = await GetServerTimeZones(connection, true, token).ConfigureAwait(false);
         var defaultSchema = await GetDefaultSchemaAsync(connection, token: token).ConfigureAwait(false);
-        return CreateDriverInstance(connectionString, version, defaultSchema, serverTimezones, connection.Timezone);
+        var defaultTimeZoneInfo = PostgreSqlHelper.GetTimeZoneInfoForServerTimeZone(connection.Timezone);
+        return CreateDriverInstance(connectionString, version, defaultSchema, defaultTimeZoneInfo);
       }
     }
 
@@ -103,7 +102,7 @@ private static Version GetVersion(SqlDriverConfiguration configuration, NpgsqlCo
 
     private static SqlDriver CreateDriverInstance(
       string connectionString, Version version, DefaultSchemaInfo defaultSchema,
-      Dictionary<string, TimeSpan> timezones, string defaultTimeZone)
+      TimeZoneInfo defaultTimeZone)
     {
       var coreServerInfo = new CoreServerInfo {
         ServerVersion = version,
@@ -116,7 +115,6 @@ private static SqlDriver CreateDriverInstance(
       var pgsqlServerInfo = new PostgreServerInfo() {
         InfinityAliasForDatesEnabled = InfinityAliasForDatesEnabled,
         LegacyTimestampBehavior = LegacyTimestamptBehaviorEnabled,
-        ServerTimeZones = timezones,
         DefaultTimeZone = defaultTimeZone
       };
 
@@ -204,44 +202,7 @@ await SqlHelper.NotifyConnectionInitializingAsync(accessors,
       }
     }
 
-    private static async ValueTask<Dictionary<string, TimeSpan>> GetServerTimeZones(NpgsqlConnection connection, bool isAsync, CancellationToken token = default)
-    {
-      var resultZones = new Dictionary<string, TimeSpan>();
-
-      var command = connection.CreateCommand();
-      command.CommandText = "SELECT \"name\", \"abbrev\", \"utc_offset\", \"is_dst\" FROM pg_timezone_names";
-      if (isAsync) {
-        await using(command)
-        await using(var reader = await command.ExecuteReaderAsync()) {
-          while(await reader.ReadAsync()) {
-            ReadTimezoneRow(reader, resultZones);
-          }
-        }
-      }
-      else {
-        using (command)
-        using (var reader = command.ExecuteReader()) {
-          while (reader.Read()) {
-            ReadTimezoneRow(reader, resultZones);
-          }
-        }
-      }
-      return resultZones;
-
-
-      static void ReadTimezoneRow(NpgsqlDataReader reader, Dictionary<string, TimeSpan> zones)
-      {
-        var name = reader.GetString(0);
-        var abbrev = reader.GetString(1);
-        var utcOffset = PostgreSqlHelper.ResurrectTimeSpanFromNpgsqlInterval(reader.GetFieldValue<NpgsqlTypes.NpgsqlInterval>(2));
-
-        _ = zones.TryAdd(name, utcOffset);
-        //flatten results for search convinience
-        if (!string.IsNullOrEmpty(abbrev)) {
-          _ = zones.TryAdd(abbrev, utcOffset);
-        }
-      }
-    }
+    #region Helpers
 
     private static bool SetOrGetExistingDisableInfinityAliasForDatesSwitch(bool valueToSet) =>
       GetSwitchValueOrSet(Orm.PostgreSql.WellKnown.DateTimeToInfinityConversionSwitchName, valueToSet);
@@ -260,6 +221,8 @@ private static bool GetSwitchValueOrSet(string switchName, bool valueToSet)
       }
     }
 
+    #endregion
+
     static DriverFactory()
     {
       // Starging from Npgsql 6.0 they broke compatibility by forcefully replacing

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/PostgreServerInfo.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Text.RegularExpressions;
 
 namespace Xtensive.Sql.Drivers.PostgreSql
 {
@@ -27,13 +28,10 @@ internal sealed class PostgreServerInfo
     public bool LegacyTimestampBehavior { get; init; }
 
     /// <summary>
-    /// Contains server timezone names and their base Utc offset (including abbreviations).
+    /// Gets the <see cref="TimeZoneInfo"/> to which <see cref="DateTimeOffset"/> values
+    /// will be converted on reading from database.
+    /// <see langword="null"/> if no local equivalent of server time zone.
     /// </summary>
-    public IReadOnlyDictionary<string, TimeSpan> ServerTimeZones { get; init; }
-
-    /// <summary>
-    /// Gets time zone of connection after connection initialization script was executed.
-    /// </summary>
-    public string DefaultTimeZone { get; init; }
+    public TimeZoneInfo DefaultTimeZone { get; init; }
   }
 }

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/v8_0/TypeMapper.cs

@@ -5,13 +5,11 @@
 // Created:    2009.06.23
 
 using System;
-using System.Collections.Generic;
 using System.Data;
 using System.Data.Common;
 using System.Security;
 using Npgsql;
 using NpgsqlTypes;
-using Xtensive.Orm.PostgreSql;
 using Xtensive.Reflection.PostgreSql;
 
 
@@ -27,7 +25,7 @@ internal class TypeMapper : Sql.TypeMapper
     private const long TimeSpanMaxValueAdjustedTicks = 9223372036854775800;
 
     protected readonly bool legacyTimestampBehaviorEnabled;
-    protected readonly TimeSpan? defaultTimeZone;
+    protected readonly TimeZoneInfo defaultTimeZone;
 
     public override bool IsParameterCastRequired(Type type)
     {
@@ -158,7 +156,7 @@ public override void BindDateTime(DbParameter parameter, object value)
         // in Npgsql 6+, though both types have the same range of values and resolution.
         //
         // If no explicit type declared it seems to be identified by DateTime value's Kind,
-        // so now we have to unbox-box value to change kind of value because of this "talanted" person.
+        // so now we have to unbox-box value to change kind of value.
         nativeParameter.NpgsqlDbType = NpgsqlDbType.Timestamp;
         nativeParameter.Value = value is null
           ? DBNull.Value
@@ -180,7 +178,6 @@ public override void BindDateTimeOffset(DbParameter parameter, object value)
         nativeParameter.NpgsqlDbType = NpgsqlDbType.TimestampTz;
 
         // Manual switch to universal time is required by Npgsql from now on,
-        // Npgsql team "untaught" the library to do it.
         nativeParameter.NpgsqlValue = value is null
           ? DBNull.Value
           : value is DateTimeOffset dateTimeOffset
@@ -300,23 +297,22 @@ public override object ReadDateTimeOffset(DbDataReader reader, int index)
         return value;
       }
       else {
-        // Here, we try to apply connection timezone to the values we read.
-        // To not get it from internal connection of DbDataReader
-        // we assume that time zone switch happens (if happens)
-        // in DomainConfiguration.ConnectionInitializationSql and
-        // we cache time zone of native connection after the script
-        // has been executed.
-
-        return (defaultTimeZone.HasValue)
-          ? value.ToOffset(defaultTimeZone.Value)
-          : value.ToLocalTime();
+        // Here, we try to apply connection time zone (if it was recongized on client-side)
+        // to the values we read.
+        // If any time zone change happens, we assume that DomainConfiguration.ConnectionInitializationSql
+        // is used to make such change and we cache time zone info on first connection in driver factory
+        // after initialization has happened.
+        // If connection time zone has not been recognized we transform value to local offset
+        // on the assumption that database server is usually in the same region.
+        return defaultTimeZone is not null
+          ?  TimeZoneInfo.ConvertTime(value, defaultTimeZone)
+          : (object) value.ToLocalTime();
       }
     }
 
-    internal protected ArgumentException ValueNotOfTypeError(string typeName)
-    {
-      return new ArgumentException($"Value is not of '{typeName}' type.");
-    }
+    internal protected ArgumentException ValueNotOfTypeError(string typeName) =>
+      new($"Value is not of '{typeName}' type.");
+
 
     // Constructors
 
@@ -325,11 +321,7 @@ public TypeMapper(PostgreSql.Driver driver)
     {
       var postgreServerInfo = driver.PostgreServerInfo;
       legacyTimestampBehaviorEnabled = postgreServerInfo.LegacyTimestampBehavior;
-      defaultTimeZone = postgreServerInfo.ServerTimeZones.TryGetValue(
-          PostgreSqlHelper.TryGetZoneFromPosix(postgreServerInfo.DefaultTimeZone), out var offset)
-        ? offset
-        : null;
-      ;
+      defaultTimeZone = postgreServerInfo.DefaultTimeZone;
     }
   }
 }