Add config. parameter DefaultTimeZone.

builds/install/misc/firebird.conf.in

@@ -706,6 +706,17 @@
 #
 #DummyPacketInterval = 0
 
+#
+# Default session or client time zone.
+#
+# If empty, the default is the OS time zone.
+# When set in the server, it defines the default session time zone for attachments.
+# When set in the client, it defines the default time zone used with client-side API functions.
+#
+# Type: string
+#
+#DefaultTimeZone =
+
 
 # ----------------------------
 # TCP Protocol Settings

doc/sql.extensions/README.time_zone.md

@@ -4,7 +4,7 @@ Time zone support consists of `TIME WITH TIME ZONE` and `TIMESTAMP WITH TIME ZON
 
 The first important thing to understand is that `TIME WITHOUT TIME ZONE`, `TIMESTAMP WITHOUT TIME ZONE` and `DATE` data types are defined to use the session time zone when converting from or to a `TIME WITH TIME ZONE` or `TIMESTAMP WITH TIME ZONE`. `TIME` and `TIMESTAMP` are synonymous to theirs respectively `WITHOUT TIME ZONE` data types.
 
-The session time zone, as the name implies, can be a different one for each database attachment. It can be set with the isc_dpb_session_time_zone DPB, and if not, it starts by default defined to be the same time zone used by the Firebird database OS process.
+The session time zone, as the name implies, can be a different one for each database attachment. It can be set with the isc_dpb_session_time_zone DPB, and if not, it starts by default defined to be the `firebird.conf` parameter `DefaultTimeZone` or the same time zone used by the Firebird OS process when the parameter is not defined. A change in `DefaultTimeZone` configuration or the OS time zone does not changes the default of a running Firebird process.
 
 It can then be changed with `SET TIME ZONE` statement to a given time zone or reset to its original value with `SET TIME ZONE LOCAL`.
 

src/common/TimeZoneUtil.cpp

@@ -33,6 +33,7 @@
 #include "../common/classes/rwlock.h"
 #include "../common/classes/timestamp.h"
 #include "../common/classes/GenericMap.h"
+#include "../common/config/config.h"
 #include "unicode/ucal.h"
 
 #ifdef TZ_UPDATE
@@ -195,6 +196,7 @@ USHORT TimeZoneUtil::getSystemTimeZone()
 	static volatile USHORT cachedTimeZoneId = TimeZoneUtil::GMT_ZONE;
 	static volatile int32_t cachedTimeZoneNameLen = -1;
 	static UChar cachedTimeZoneName[TimeZoneUtil::MAX_SIZE];
+	static GlobalPtr<RWLock> lock;
 
 	if (cachedError)
 		return cachedTimeZoneId;
@@ -203,9 +205,21 @@ USHORT TimeZoneUtil::getSystemTimeZone()
 	Jrd::UnicodeUtil::ConversionICU& icuLib = Jrd::UnicodeUtil::getConversionICU();
 
 	UChar buffer[TimeZoneUtil::MAX_SIZE];
-	int32_t len = icuLib.ucalGetDefaultTimeZone(buffer, FB_NELEM(buffer), &icuErrorCode);
+	int32_t len;
+	const char* configDefault = Config::getDefaultTimeZone();
 
-	static GlobalPtr<RWLock> lock;
+	if (configDefault && configDefault[0])
+	{
+		UChar* dst = buffer;
+
+		for (const char* src = configDefault; src - configDefault < TimeZoneUtil::MAX_SIZE && *src; ++src, ++dst)
+			*dst = *src;
+
+		*dst = 0;
+		len = dst - buffer;
+	}
+	else
+		len = icuLib.ucalGetDefaultTimeZone(buffer, FB_NELEM(buffer), &icuErrorCode);
 
 	ReadLockGuard readGuard(lock, "TimeZoneUtil::getSystemTimeZone");
 

src/common/config/config.cpp

@@ -151,6 +151,7 @@ const Config::ConfigEntry Config::entries[MAX_CONFIG_KEY] =
 	{TYPE_INTEGER,		"DefaultDbCachePages",		(ConfigValue) -1},			// pages
 	{TYPE_INTEGER,		"ConnectionTimeout",		(ConfigValue) 180},			// seconds
 	{TYPE_INTEGER,		"DummyPacketInterval",		(ConfigValue) 0},			// seconds
+	{TYPE_STRING,		"DefaultTimeZone",			(ConfigValue) ""},
 	{TYPE_INTEGER,		"LockMemSize",				(ConfigValue) 1048576},		// bytes
 	{TYPE_INTEGER,		"LockHashSlots",			(ConfigValue) 8191},		// slots
 	{TYPE_INTEGER,		"LockAcquireSpins",			(ConfigValue) 0},
@@ -517,6 +518,11 @@ int Config::getDummyPacketInterval() const
 	return get<int>(KEY_DUMMY_PACKET_INTERVAL);
 }
 
+const char* Config::getDefaultTimeZone()
+{
+	return getDefaultConfig()->get<const char*>(KEY_DEFAULT_TIME_ZONE);
+}
+
 int Config::getLockMemSize() const
 {
 	int size = get<int>(KEY_LOCK_MEM_SIZE);

src/common/config/config.h

@@ -98,6 +98,7 @@ public:
 		KEY_DEFAULT_DB_CACHE_PAGES,
 		KEY_CONNECTION_TIMEOUT,
 		KEY_DUMMY_PACKET_INTERVAL,
+		KEY_DEFAULT_TIME_ZONE,
 		KEY_LOCK_MEM_SIZE,
 		KEY_LOCK_HASH_SLOTS,
 		KEY_LOCK_ACQUIRE_SPINS,
@@ -263,6 +264,8 @@ public:
 	// Dummy packet interval
 	int getDummyPacketInterval() const;
 
+	static const char* getDefaultTimeZone();
+
 	// Lock manager memory size
 	int getLockMemSize() const;