Add. Support multiple database backends.

```Lua
local Database = require 'resources.functions.database'

-- Default backend configured via xml_handler.db_backend = 'native'
dbh = Database.new("system")

-- To use other backends you can use
dbh = Database.backend.luasql("system")
```

resources/install/scripts/odbc_pool.lua

@@ -0,0 +1,67 @@
+-- Start background service to support Lua-ODBC-Pool database backend
+
+require "resources.functions.config"
+require "resources.functions.file_exists"
+
+local log      = require "resources.functions.log".dbpool
+local odbc     = require "odbc"
+local odbcpool = require "odbc.pool"
+
+-- Configuration
+local POLL_TIMEOUT = 5
+local run_file = scripts_dir .. "/run/dbpool.tmp";
+
+-- Pool ctor
+local function run_odbc_pool(name, n)
+  local connection_string = assert(database[name])
+
+  local typ, dsn, user, password = connection_string:match("^(.-)://(.-):(.-):(.-)$")
+  assert(typ == 'odbc', "unsupported connection string:" .. connection_string)
+
+  local cli = odbcpool.client(name)
+
+  log.noticef("Starting reconnect thread[%s] ...", name)
+  local rthread = odbcpool.reconnect_thread(cli, dsn, user, password)
+  rthread:start()
+  log.noticef("Reconnect thread[%s] started", name)
+
+  local env = odbc.environment()
+
+  local connections = {}
+  for i = 1, (n or 10) do
+    local cnn = odbc.assert(env:connection())
+    connections[#connections+1] = cnn
+    cli:reconnect(cnn)
+  end
+
+  return {
+    name = name;
+    cli  = cli;
+    cnn  = connections;
+    thr  = rthread;
+  }
+end
+
+local function stop_odbc_pool(ctx)
+  log.noticef("Stopping reconnect thread[%s] ...", ctx.name)
+  ctx.thr:stop()
+  log.noticef("Reconnect thread[%s] stopped", ctx.name)
+end
+
+local function main()
+  local system_pool = run_odbc_pool("system", 10)
+  local switch_pool = run_odbc_pool("switch", 10)
+
+  local file = assert(io.open(run_file, "w"));
+  file:write("remove this file to stop the script");
+  file:close()
+
+  while file_exists(run_file) do
+    freeswitch.msleep(POLL_TIMEOUT*1000)
+  end
+
+  stop_odbc_pool(system_pool)
+  stop_odbc_pool(switch_pool)
+end
+
+main()

resources/install/scripts/resources/functions/database.lua

@@ -1,120 +1,30 @@
+---
+-- @usage 
+--  -- Use default backend
+--  dbh = Database.new("system")
+--  .....
+--
+-- @usage 
+--  -- Use LuaSQL backend
+--  dbh = Database.backend.luasql("system")
+--  .....
+
 require 'resources.functions.config'
 
------------------------------------------------------------
+local log = require "resources.functions.log".database
-local OdbcDatabase = {} if not freeswitch then
-OdbcDatabase.__index = OdbcDatabase
 
-local odbc = require "odbc.dba"
+local BACKEND = xml_handler and xml_handler.db_backend or 'native'
-
-function OdbcDatabase.new(name)
-  local self = setmetatable({}, OdbcDatabase)
-
-  local connection_string = assert(database[name])
-
-  local typ, dsn, user, password = connection_string:match("^(.-)://(.-):(.-):(.-)$")
-  assert(typ == 'odbc', "unsupported connection string:" .. connection_string)
-
-  self._dbh = odbc.Connect(dsn, user, password)
-
-  return self
-end
-
-function OdbcDatabase:query(sql, fn)
-  self._rows_affected = nil
-  if fn then
-    return self._dbh:neach(sql, function(row)
-      local o = {}
-      for k, v in pairs(row) do
-        if v == odbc.NULL then 
-          o[k] = nil
-        else
-          o[k] = tostring(v)
-        end
-      end
-      return fn(o)
-    end)
-  end
-  local ok, err = self._dbh:exec(sql)
-  if not ok then return nil, err end
-  self._rows_affected = ok
-  return self._rows_affected
-end
-
-function OdbcDatabase:affected_rows()
-  return self._rows_affected;
-end
-
-function OdbcDatabase:release()
-  if self._dbh then
-    self._dbh:destroy()
-    self._dbh = nil
-  end
-end
-
-function OdbcDatabase:connected()
-  return self._dbh and self._dbh:connected()
-end
-
-end
------------------------------------------------------------
 
 -----------------------------------------------------------
-local FsDatabase = {} if freeswitch then
+local installed_classes = {}
+local default_backend = FsDatabase
+local function new_database(backend)
+  local class = installed_classes[backend]
+  if class then return class end
 
-require "resources.functions.file_exists"
-require "resources.functions.database_handle"
-
-FsDatabase.__index = FsDatabase
-
-function FsDatabase.new(name)
-  local dbh = assert(name)
-  if type(name) == 'string' then
-    if name == 'switch' and file_exists(database_dir.."/core.db") then
-      dbh = freeswitch.Dbh("sqlite://"..database_dir.."/core.db")
-    else
-      dbh = database_handle(name)
-    end
-  end
-  assert(dbh:connected())
-
-  local self = setmetatable({
-    _dbh = dbh;
-  }, FsDatabase)
-
-  return self
-end
-
-function FsDatabase:query(sql, fn)
-  if fn then
-    return self._dbh:query(sql, fn)
-  end
-  return self._dbh:query(sql)
-end
-
-function FsDatabase:affected_rows()
-  if self._dbh then
-    return self._dbh:affected_rows()
-  end
-end
-
-function FsDatabase:release()
-  if self._dbh then
-    self._dbh:release()
-    self._dbh = nil
-  end
-end
-
-function FsDatabase:connected()
-  return self._dbh and self._dbh:connected()
-end
-
-end
------------------------------------------------------------
-
------------------------------------------------------------
   local Database = {} do
   Database.__index = Database
-Database.__base = freeswitch and FsDatabase or OdbcDatabase
+  Database.__base = backend or default_backend
   Database = setmetatable(Database, Database.__base)
 
   function Database.new(...)
@@ -160,7 +70,9 @@ function Database:fetch_all(sql)
   end
 
   function Database.__self_test__(...)
+    log.info('self_test Database - ' ..  Database._backend_name)
     local db = Database.new(...)
+
     assert(db:connected())
 
     assert("1" == db:first_value("select 1 as v union all select 2 as v"))
@@ -179,11 +91,45 @@ function Database.__self_test__(...)
 
     -- assert(nil == db:first_value("some non sql query"))
 
+    -- select NULL
+    local a = assert(db:first_value("select NULL as a"))
+    assert(a == "")
+
     db:release()
     assert(not db:connected())
-  print(" * databse - OK!")
+    log.info('self_test Database - pass')
   end
 
+  end
+
+  installed_classes[backend] = Database
+  return Database
+end
+-----------------------------------------------------------
+
+-----------------------------------------------------------
+local Database = {} do 
+
+local backend_loader = setmetatable({}, {__index = function(self, backend)
+  local class = require("resources.functions.database." .. backend)
+  local database = new_database(class)
+  self[backend] = function(...)
+    return database.new(...)
+  end
+  return self[backend]
+end})
+
+Database.backend = backend_loader
+
+Database.new = Database.backend[BACKEND]
+
+Database.__self_test__ = function(backends, ...)
+  for _, backend in ipairs(backends) do
+    local t = Database.backend[backend]
+    t(...).__self_test__(...)
+  end
+end;
+
 end
 -----------------------------------------------------------
 

resources/install/scripts/resources/functions/database/luasql.lua

@@ -0,0 +1,102 @@
+--
+-- LuaSQL backend to FusionPBX database class
+--
+
+require "resources.functions.split"
+local log  = require "resources.functions.log".database
+
+local LuaSQLDatabase = {} do
+LuaSQLDatabase.__index = LuaSQLDatabase
+LuaSQLDatabase._backend_name = 'LuaSQL'
+
+local map = {
+  pgsql = 'postgres';
+}
+
+local function apply_names(row, colnames, null_value)
+  for _, name in pairs(colnames) do
+    if row[name] == nil then
+      row[name] = null_value
+    else
+      row[name] = tostring(row[name])
+    end
+  end
+  return row
+end
+
+function LuaSQLDatabase.new(name)
+  local self = setmetatable({}, OdbcDatabase)
+
+  local connection_string = assert(database[name])
+
+  local typ, args = split_first(database[name], "://", true);
+  typ = map[typ] or typ
+
+  local luasql = require ("luasql." .. typ)
+  local env = assert (luasql[typ]())
+  local dbh = assert (env:connect( usplit(args, ':', true) ))
+
+  self._env, self._dbh = env, dbh
+  return self
+end
+
+function LuaSQLDatabase:query(sql, fn)
+  self._rows_affected = nil
+
+  if fn then
+    local cur, err = self._dbh:execute(sql)
+    if err and not cur then
+      log.errf("Can not execute sql: %s\n%s", tostring(err), sql)
+    end
+
+    local colnames = cur:getcolnames()
+    while true do
+      local row, err = cur:fetch({}, "a")
+      if not row then break end
+      local ok, ret = pcall(fn, apply_names(row, colnames, ""))
+      if (not ok) or (type(ret) == 'number' and ret > 0) then
+        break
+      end
+    end
+    cur:close()
+
+    return true
+  end
+
+  local ok, err = self._dbh:execute(sql)
+  if err and not ok then
+    log.errf("Can not execute sql: %s\n%s", tostring(err), sql)
+  end
+
+  if not ok then return nil, err end
+
+  if type(ok) ~= 'number' then
+    ok:close()
+    log.warning('SQL return recordset')
+  else
+    self._rows_affected = ok
+  end
+
+  self._rows_affected = ok
+  return self._rows_affected
+end
+
+function LuaSQLDatabase:affected_rows()
+  return self._rows_affected;
+end
+
+function LuaSQLDatabase:release()
+  if self._dbh then
+    self._dbh:close()
+    self._env:close()
+    self._env, self._dbh = nil
+  end
+end
+
+function LuaSQLDatabase:connected()
+  return self._dbh and self._dbh:connected()
+end
+
+end
+
+return LuaSQLDatabase

resources/install/scripts/resources/functions/database/native.lua

@@ -0,0 +1,61 @@
+--
+-- Native backend to FusionPBX database class
+--
+
+local log = require "resources.functions.log".database
+
+-----------------------------------------------------------
+local FsDatabase = {} if freeswitch then
+
+require "resources.functions.file_exists"
+require "resources.functions.database_handle"
+
+FsDatabase.__index = FsDatabase
+FsDatabase._backend_name = 'native'
+
+function FsDatabase.new(name)
+  local dbh = assert(name)
+  if type(name) == 'string' then
+    if name == 'switch' and file_exists(database_dir.."/core.db") then
+      dbh = freeswitch.Dbh("sqlite://"..database_dir.."/core.db")
+    else
+      dbh = database_handle(name)
+    end
+  end
+  assert(dbh:connected())
+
+  local self = setmetatable({
+    _dbh = dbh;
+  }, FsDatabase)
+
+  return self
+end
+
+function FsDatabase:query(sql, fn)
+  if fn then
+    return self._dbh:query(sql, fn)
+  end
+  return self._dbh:query(sql)
+end
+
+function FsDatabase:affected_rows()
+  if self._dbh then
+    return self._dbh:affected_rows()
+  end
+end
+
+function FsDatabase:release()
+  if self._dbh then
+    self._dbh:release()
+    self._dbh = nil
+  end
+end
+
+function FsDatabase:connected()
+  return self._dbh and self._dbh:connected()
+end
+
+end
+-----------------------------------------------------------
+
+return FsDatabase

resources/install/scripts/resources/functions/database/odbc.lua

@@ -0,0 +1,67 @@
+--
+-- Lua-ODBC backend to FusionPBX database class
+--
+
+local log  = require "resources.functions.log".database
+local odbc = require "odbc.dba"
+
+local function remove_null(row, null, null_value)
+  local o = {}
+  for k, v in pairs(row) do
+    if v == null then 
+      o[k] = null_value
+    else
+      o[k] = tostring(v)
+    end
+  end
+  return o
+end
+
+local OdbcDatabase = {} do
+OdbcDatabase.__index = OdbcDatabase
+OdbcDatabase._backend_name = 'ODBC'
+
+function OdbcDatabase.new(name)
+  local self = setmetatable({}, OdbcDatabase)
+
+  local connection_string = assert(database[name])
+
+  local typ, dsn, user, password = connection_string:match("^(.-)://(.-):(.-):(.-)$")
+  assert(typ == 'odbc', "unsupported connection string:" .. connection_string)
+
+  self._dbh = odbc.Connect(dsn, user, password)
+
+  return self
+end
+
+function OdbcDatabase:query(sql, fn)
+  self._rows_affected = nil
+  if fn then
+    return self._dbh:neach(sql, function(row)
+      return fn(remove_null(row, odbc.NULL, ""))
+    end)
+  end
+  local ok, err = self._dbh:exec(sql)
+  if not ok then return nil, err end
+  self._rows_affected = ok
+  return self._rows_affected
+end
+
+function OdbcDatabase:affected_rows()
+  return self._rows_affected;
+end
+
+function OdbcDatabase:release()
+  if self._dbh then
+    self._dbh:destroy()
+    self._dbh = nil
+  end
+end
+
+function OdbcDatabase:connected()
+  return self._dbh and self._dbh:connected()
+end
+
+end
+
+return OdbcDatabase

resources/install/scripts/resources/functions/database/odbcpool.lua

@@ -0,0 +1,82 @@
+--
+-- Lua-ODBC-Pool backend to FusionPBX database class
+--
+
+local log      = require "resources.functions.log".database
+local odbc     = require "odbc.dba"
+local odbcpool = require "odbc.dba.pool"
+
+local function remove_null(row, null, null_value)
+  local o = {}
+  for k, v in pairs(row) do
+    if v == null then 
+      o[k] = null_value
+    else
+      o[k] = tostring(v)
+    end
+  end
+  return o
+end
+
+-----------------------------------------------------------
+local OdbcPoolDatabase = {} do
+OdbcPoolDatabase.__index = OdbcPoolDatabase
+OdbcPoolDatabase._backend_name = 'ODBC Pool'
+
+function OdbcPoolDatabase.new(name)
+  local self = setmetatable({}, OdbcPoolDatabase)
+  self._cli           = odbcpool.client(name)
+  self._timeout       = 1000
+  self._rows_affected = nil
+  return self
+end
+
+function OdbcPoolDatabase:query(sql, fn)
+  self._rows_affected = nil
+  local cli = self._cli
+
+  local ok, err
+  if fn then
+    ok, err = cli:acquire(self._timeout, function(dbh)
+      local ok, err = dbh:neach(sql, function(row)
+        return fn(remove_null(row, odbc.NULL, ""))
+      end)
+      if err and not ok then
+        log.errf("Can not execute sql: %s\n%s", tostring(err), sql)
+      end
+      return not not dbh:connected(), true
+    end)
+  else
+    ok, err = cli:acquire(self._timeout, function(dbh)
+      local ok, err = dbh:exec(sql)
+      if err and not ok then
+        log.errf("Can not execute sql: %s\n%s", tostring(err), sql)
+      end
+      self._rows_affected = ok
+      return not not dbh:connected(), ok
+    end)
+  end
+
+  if err and not ok then
+    log.errf("Can not get database handle: %s", tostring(err))
+  end
+
+  return ok
+end
+
+function OdbcPoolDatabase:affected_rows()
+  return self._rows_affected;
+end
+
+function OdbcPoolDatabase:release()
+  self._cli = nil
+end
+
+function OdbcPoolDatabase:connected()
+  return not not self._cli
+end
+
+end
+-----------------------------------------------------------
+
+return OdbcPoolDatabase

resources/install/scripts/self_test.lua

@@ -0,0 +1,12 @@
+local Cache    = require 'resources.functions.cache'
+local Database = require 'resources.functions.database'
+
+Database.__self_test__({
+  "native",
+  "luasql",
+  "odbc",
+  "odbcpool",
+},
+"system")
+
+Cache._self_test()