Cache logger instance.

- Nim 2.x has moved the DB connectors outside the standard library to
  the `db_connector` package.
- Refactor the pooling implementation and macro expectations to use the
  `withConnection` name instead of `withConn`. This change allows a
  caller to use a [waterpark](https://github.com/guzba/waterpark) pool
  instance instead of the builtin pool instance. Waterpark provides
  better support for multi-threaded environments. The builtin pooling
  mechanism may be deprecated in favor of waterpark in the future.
- Add the `getModelIfItExists` generated proc to the list of standard
  procs we generate. This is a flavour of `getModel` that returns an
  `Option` instead of raising an exception when there is no model for
  the given id.
- Change `PaginationParams#orderBy` to accept a `seq[string]` to allow
  for sorting on multiple fields.

README.rst

@@ -57,7 +57,7 @@ Models may be defined as:
 
 .. code-block:: Nim
    # models.nim
-   import std/options, std/times
+   import std/[options, times]
    import uuids
 
    type
@@ -82,6 +82,8 @@ Using Fiber ORM we can generate a data access layer with:
 
 .. code-block:: Nim
    # db.nim
+   import std/[options]
+   import db_connectors/db_postgres
    import fiber_orm
    import ./models.nim
 
@@ -102,6 +104,7 @@ This will generate the following procedures:
 
 .. code-block:: Nim
    proc getTodoItem*(db: TodoDB, id: UUID): TodoItem;
+   proc getTodoItemIfItExists*(db: TodoDB, id: UUID): Option[TodoItem];
    proc getAllTodoItems*(db: TodoDB): seq[TodoItem];
    proc createTodoItem*(db: TodoDB, rec: TodoItem): TodoItem;
    proc updateTodoItem*(db: TodoDB, rec: TodoItem): bool;
@@ -112,6 +115,7 @@ This will generate the following procedures:
      values: varargs[string, dbFormat]): seq[TodoItem];
 
    proc getTimeEntry*(db: TodoDB, id: UUID): TimeEntry;
+   proc getTimeEntryIfItExists*(db: TodoDB, id: UUID): Option[TimeEntry];
    proc getAllTimeEntries*(db: TodoDB): seq[TimeEntry];
    proc createTimeEntry*(db: TodoDB, rec: TimeEntry): TimeEntry;
    proc updateTimeEntry*(db: TodoDB, rec: TimeEntry): bool;

fiber_orm.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "2.0.0"
+version       = "3.1.1"
 author        = "Jonathan Bernard"
 description   = "Lightweight Postgres ORM for Nim."
 license       = "GPL-3.0"
@@ -11,4 +11,4 @@ srcDir        = "src"
 # Dependencies
 
 requires @["nim >= 1.4.0", "uuids"]
-requires "https://git.jdb-software.com/jdb/nim-namespaced-logging.git"
+requires "namespaced_logging >= 1.0.0"

src/fiber_orm.nim

@@ -1,6 +1,6 @@
 # Fiber ORM
 #
-# Copyright 2019 Jonathan Bernard <jonathan@jdbernard.com>
+# Copyright 2019-2024 Jonathan Bernard <jonathan@jdbernard.com>
 
 ## Lightweight ORM supporting the `Postgres`_ and `SQLite`_ databases in Nim.
 ## It supports a simple, opinionated model mapper to generate SQL queries based
@@ -107,6 +107,7 @@
 ##
 ##    proc createTodoItem*(db: TodoDB, rec: TodoItem): TodoItem;
 ##    proc updateTodoItem*(db: TodoDB, rec: TodoItem): bool;
+##    proc createOrUpdateTodoItem*(db: TodoDB, rec: TodoItem): bool;
 ##    proc deleteTodoItem*(db: TodoDB, rec: TodoItem): bool;
 ##    proc deleteTodoItem*(db: TodoDB, id: UUID): bool;
 ##
@@ -263,62 +264,64 @@
 ## In the example above the `pool.DbConnPool`_ object is used as database
 ## object type (aliased as `TodoDB`). This is the intended usage pattern, but
 ## anything can be passed as the database object type so long as there is a
-## defined `withConn` template that provides an injected `conn: DbConn` object
+## defined `withConnection` template that provides a `conn: DbConn` object
 ## to the provided statement body.
 ##
 ## For example, a valid database object implementation that opens a new
 ## connection for every request might look like this:
 ##
 ## .. code-block:: Nim
-##    import std/db_postgres
+##    import db_connector/db_postgres
 ##
 ##    type TodoDB* = object
 ##      connString: string
 ##
-##    template withConn*(db: TodoDB, stmt: untyped): untyped =
-##      let conn {.inject.} = open("", "", "", db.connString)
-##      try: stmt
-##      finally: close(conn)
+##    template withConnection*(db: TodoDB, stmt: untyped): untyped =
+##      block:
+##        let conn = open("", "", "", db.connString)
+##        try: stmt
+##        finally: close(conn)
 ##
 ## .. _pool.DbConnPool: fiber_orm/pool.html#DbConnPool
 ##
-import std/db_postgres, std/macros, std/options, std/sequtils, std/strutils
+import std/[json, macros, options, sequtils, strutils]
+import db_connector/db_common
 import namespaced_logging, uuids
 
 from std/unicode import capitalize
 
+import ./fiber_orm/db_common as fiber_db_common
 import ./fiber_orm/pool
 import ./fiber_orm/util
 
-export
-  pool,
-  util.columnNamesForModel,
-  util.dbFormat,
-  util.dbNameToIdent,
-  util.identNameToDb,
-  util.modelName,
-  util.rowToModel,
-  util.tableName
+export pool, util
 
 type
-  PaginationParams* = object
-    pageSize*: int
-    offset*: int
-    orderBy*: Option[string]
-
   PagedRecords*[T] = object
     pagination*: Option[PaginationParams]
     records*: seq[T]
     totalRecords*: int
 
+  DbUpdateError* = object of CatchableError ##\
+    ## Error types raised when a DB modification fails.
+
   NotFoundError* = object of CatchableError ##\
     ## Error type raised when no record matches a given ID
 
-var logNs {.threadvar.}: LoggingNamespace
+var logService {.threadvar.}: Option[LogService]
+var logger {.threadvar.}: Option[Logger]
 
-template log(): untyped =
-  if logNs.isNil: logNs = initLoggingNamespace(name = "fiber_orm", level = lvlNotice)
-  logNs
+proc logQuery*(methodName: string, sqlStmt: string, args: openArray[(string, string)] = []) =
+  # namespaced_logging would do this check for us, but we don't want to even
+  # build the log object if we're not actually logging
+  if logService.isNone: return
+  if logger.isNone: logger = logService.getLogger("fiber_orm/query")
+  var log = %*{ "method": methodName, "sql": sqlStmt }
+  for (k, v) in args: log[k] = %v
+  logger.debug(log)
+
+proc enableDbLogging*(svc: LogService) =
+  logService = some(svc)
 
 proc newMutateClauses(): MutateClauses =
   return MutateClauses(
@@ -326,7 +329,7 @@ proc newMutateClauses(): MutateClauses =
     placeholders: @[],
     values: @[])
 
-proc createRecord*[T](db: DbConn, rec: T): T =
+proc createRecord*[D: DbConnType, T](db: D, rec: T): T =
   ## Create a new record. `rec` is expected to be a `model class`_. The `id`
   ## field is only set if it is non-empty (see `ID Field`_ for details).
   ##
@@ -344,12 +347,12 @@ proc createRecord*[T](db: DbConn, rec: T): T =
     " VALUES (" & mc.placeholders.join(",") & ") " &
     " RETURNING " & columnNamesForModel(rec).join(",")
 
-  log().debug "createRecord: [" & sqlStmt & "]"
+  logQuery("createRecord", sqlStmt)
   let newRow = db.getRow(sql(sqlStmt), mc.values)
 
   result = rowToModel(T, newRow)
 
-proc updateRecord*[T](db: DbConn, rec: T): bool =
+proc updateRecord*[D: DbConnType, T](db: D, rec: T): bool =
   ## Update a record by id. `rec` is expected to be a `model class`_.
   var mc = newMutateClauses()
   populateMutateClauses(rec, false, mc)
@@ -360,33 +363,51 @@ proc updateRecord*[T](db: DbConn, rec: T): bool =
     " SET " & setClause &
     " WHERE id = ? "
 
-  log().debug "updateRecord: [" & sqlStmt & "] id: " & $rec.id
+  logQuery("updateRecord", sqlStmt, [("id", $rec.id)])
   let numRowsUpdated = db.execAffectedRows(sql(sqlStmt), mc.values.concat(@[$rec.id]))
 
   return numRowsUpdated > 0;
 
-template deleteRecord*(db: DbConn, modelType: type, id: typed): untyped =
+proc createOrUpdateRecord*[D: DbConnType, T](db: D, rec: T): T =
+  ## Create or update a record. `rec` is expected to be a `model class`_. If
+  ## the `id` field is unset, or if there is no existing record with the given
+  ## id, a new record is inserted. Otherwise, the existing record is updated.
+  ##
+  ## Note that this does not perform partial updates, all fields are updated.
+
+  let findRecordStmt = "SELECT id FROM " & tableName(rec) & " WHERE id = ?"
+  logQuery("createOrUpdateRecord", findRecordStmt, [("id", $rec.id)])
+  let rows = db.getAllRows(sql(findRecordStmt), [$rec.id])
+
+  if rows.len == 0: result = createRecord(db, rec)
+  else:
+    result = rec
+    if not updateRecord(db, rec):
+      raise newException(DbUpdateError,
+        "unable to update " & modelName(rec) & " for id " & $rec.id)
+
+template deleteRecord*[D: DbConnType](db: D, modelType: type, id: typed): untyped =
   ## Delete a record by id.
   let sqlStmt = "DELETE FROM " & tableName(modelType) & " WHERE id = ?"
-  log().debug "deleteRecord: [" & sqlStmt & "] id: " & $id
+  logQuery("deleteRecord", sqlStmt, [("id", $id)])
   db.tryExec(sql(sqlStmt), $id)
 
-proc deleteRecord*[T](db: DbConn, rec: T): bool =
+proc deleteRecord*[D: DbConnType, T](db: D, rec: T): bool =
   ## Delete a record by `id`_.
   ##
   ## .. _id: #model-class-id-field
   let sqlStmt = "DELETE FROM " & tableName(rec) & " WHERE id = ?"
-  log().debug "deleteRecord: [" & sqlStmt & "] id: " & $rec.id
+  logQuery("deleteRecord", sqlStmt, [("id", $rec.id)])
   return db.tryExec(sql(sqlStmt), $rec.id)
 
-template getRecord*(db: DbConn, modelType: type, id: typed): untyped =
+template getRecord*[D: DbConnType](db: D, modelType: type, id: typed): untyped =
   ## Fetch a record by id.
   let sqlStmt =
     "SELECT " & columnNamesForModel(modelType).join(",") &
     " FROM " & tableName(modelType) &
     " WHERE id = ?"
 
-  log().debug "getRecord: [" & sqlStmt & "] id: " & $id
+  logQuery("getRecord", sqlStmt, [("id", $id)])
   let row = db.getRow(sql(sqlStmt), @[$id])
 
   if allIt(row, it.len == 0):
@@ -394,8 +415,8 @@ template getRecord*(db: DbConn, modelType: type, id: typed): untyped =
 
   rowToModel(modelType, row)
 
-template findRecordsWhere*(
-    db: DbConn,
+template findRecordsWhere*[D: DbConnType](
+    db: D,
     modelType: type,
     whereClause: string,
     values: varargs[string, dbFormat],
@@ -412,17 +433,9 @@ template findRecordsWhere*(
     "SELECT COUNT(*) FROM " & tableName(modelType) &
     " WHERE " & whereClause
 
-  if page.isSome:
-    let p = page.get
-    if p.orderBy.isSome:
-      fetchStmt &= " ORDER BY " & p.orderBy.get
-    else:
-      fetchStmt &= " ORDER BY id"
+  if page.isSome: fetchStmt &= getPagingClause(page.get)
 
-    fetchStmt &= " LIMIT " & $p.pageSize &
-                 " OFFSET " & $p.offset
-
-  log().debug "findRecordsWhere: [" & fetchStmt & "] values: (" & values.join(", ") & ")"
+  logQuery("findRecordsWhere", fetchStmt, [("values", values.join(", "))])
   let records = db.getAllRows(sql(fetchStmt), values).mapIt(rowToModel(modelType, it))
 
   PagedRecords[modelType](
@@ -432,8 +445,8 @@ template findRecordsWhere*(
       if page.isNone: records.len
       else: db.getRow(sql(countStmt), values)[0].parseInt)
 
-template getAllRecords*(
-    db: DbConn,
+template getAllRecords*[D: DbConnType](
+    db: D,
     modelType: type,
     page: Option[PaginationParams]): untyped =
   ## Fetch all records of the given type.
@@ -443,17 +456,9 @@ template getAllRecords*(
 
   var countStmt = "SELECT COUNT(*) FROM " & tableName(modelType)
 
-  if page.isSome:
-    let p = page.get
-    if p.orderBy.isSome:
-      fetchStmt &= " ORDER BY " & p.orderBy.get
-    else:
-      fetchStmt &= " ORDER BY id"
+  if page.isSome: fetchStmt &= getPagingClause(page.get)
 
-    fetchStmt &= " LIMIT " & $p.pageSize &
-                 " OFFSET " & $p.offset
-
-  log().debug "getAllRecords: [" & fetchStmt & "]"
+  logQuery("getAllRecords", fetchStmt)
   let records = db.getAllRows(sql(fetchStmt)).mapIt(rowToModel(modelType, it))
 
   PagedRecords[modelType](
@@ -464,8 +469,8 @@ template getAllRecords*(
       else: db.getRow(sql(countStmt))[0].parseInt)
 
 
-template findRecordsBy*(
-    db: DbConn,
+template findRecordsBy*[D: DbConnType](
+    db: D,
     modelType: type,
     lookups: seq[tuple[field: string, value: string]],
     page: Option[PaginationParams]): untyped =
@@ -482,17 +487,9 @@ template findRecordsBy*(
     "SELECT COUNT(*) FROM " & tableName(modelType) &
     " WHERE " & whereClause
 
-  if page.isSome:
-    let p = page.get
-    if p.orderBy.isSome:
-      fetchStmt &= " ORDER BY " & p.orderBy.get
-    else:
-      fetchStmt &= " ORDER BY id"
+  if page.isSome: fetchStmt &= getPagingClause(page.get)
 
-    fetchStmt &= " LIMIT " & $p.pageSize &
-                 " OFFSET " & $p.offset
-
-  log().debug "findRecordsBy: [" & fetchStmt & "] values (" & values.join(", ") & ")"
+  logQuery("findRecordsBy", fetchStmt, [("values", values.join(", "))])
   let records = db.getAllRows(sql(fetchStmt), values).mapIt(rowToModel(modelType, it))
 
   PagedRecords[modelType](
@@ -515,51 +512,66 @@ macro generateProcsForModels*(dbType: type, modelTypes: openarray[type]): untype
   ##    proc deleteTodoItem*(db: TodoDB, rec: TodoItem): bool;
   ##    proc deleteTodoItem*(db: TodoDB, id: idType): bool;
   ##    proc updateTodoItem*(db: TodoDB, rec: TodoItem): bool;
+  ##    proc createOrUpdateTodoItem*(db: TodoDB, rec: TodoItem): bool;
   ##
   ##    proc findTodoItemsWhere*(
   ##      db: TodoDB, whereClause: string, values: varargs[string]): TodoItem;
   ##
-  ## `dbType` is expected to be some type that has a defined `withConn`
+  ## `dbType` is expected to be some type that has a defined `withConnection`
   ## procedure (see `Database Object`_ for details).
   ##
   ## .. _Database Object: #database-object
   result = newStmtList()
 
   for t in modelTypes:
+    if t.getType[1].typeKind == ntyRef:
+      raise newException(ValueError,
+        "fiber_orm model object must be objects, not refs")
+
     let modelName = $(t.getType[1])
     let getName = ident("get" & modelName)
+    let getIfExistsName = ident("get" & modelName & "IfItExists")
     let getAllName = ident("getAll" & pluralize(modelName))
     let findWhereName = ident("find" & pluralize(modelName) & "Where")
     let createName = ident("create" & modelName)
     let updateName = ident("update" & modelName)
+    let createOrUpdateName = ident("createOrUpdate" & modelName)
     let deleteName = ident("delete" & modelName)
     let idType = typeOfColumn(t, "id")
     result.add quote do:
       proc `getName`*(db: `dbType`, id: `idType`): `t` =
-        db.withConn: result = getRecord(conn, `t`, id)
+        db.withConnection conn: result = getRecord(conn, `t`, id)
+
+      proc `getIfExistsName`*(db: `dbType`, id: `idType`): Option[`t`] =
+        db.withConnection conn:
+          try: result = some(getRecord(conn, `t`, id))
+          except NotFoundError: result = none[`t`]()
 
       proc `getAllName`*(db: `dbType`, pagination = none[PaginationParams]()): PagedRecords[`t`] =
-        db.withConn: result = getAllRecords(conn, `t`, pagination)
+        db.withConnection conn: result = getAllRecords(conn, `t`, pagination)
 
       proc `findWhereName`*(
           db: `dbType`,
           whereClause: string,
           values: varargs[string, dbFormat],
           pagination = none[PaginationParams]()): PagedRecords[`t`] =
-        db.withConn:
+        db.withConnection conn:
           result = findRecordsWhere(conn, `t`, whereClause, values, pagination)
 
       proc `createName`*(db: `dbType`, rec: `t`): `t` =
-        db.withConn: result = createRecord(conn, rec)
+        db.withConnection conn: result = createRecord(conn, rec)
 
       proc `updateName`*(db: `dbType`, rec: `t`): bool =
-        db.withConn: result = updateRecord(conn, rec)
+        db.withConnection conn: result = updateRecord(conn, rec)
+
+      proc `createOrUpdateName`*(db: `dbType`, rec: `t`): `t` =
+        db.inTransaction: result = createOrUpdateRecord(conn, rec)
 
       proc `deleteName`*(db: `dbType`, rec: `t`): bool =
-        db.withConn: result = deleteRecord(conn, rec)
+        db.withConnection conn: result = deleteRecord(conn, rec)
 
       proc `deleteName`*(db: `dbType`, id: `idType`): bool =
-        db.withConn: result = deleteRecord(conn, `t`, id)
+        db.withConnection conn: result = deleteRecord(conn, `t`, id)
 
 macro generateLookup*(dbType: type, modelType: type, fields: seq[string]): untyped =
   ## Create a lookup procedure for a given set of field names. For example,
@@ -579,7 +591,7 @@ macro generateLookup*(dbType: type, modelType: type, fields: seq[string]): untyp
   # Create proc skeleton
   result = quote do:
     proc `procName`*(db: `dbType`): PagedRecords[`modelType`] =
-      db.withConn: result = findRecordsBy(conn, `modelType`)
+      db.withConnection conn: result = findRecordsBy(conn, `modelType`)
 
   var callParams = quote do: @[]
 
@@ -603,11 +615,11 @@ macro generateLookup*(dbType: type, modelType: type, fields: seq[string]): untyp
 
   # Add the call params to the inner procedure call
   # result[6][0][1][0][1] is
-  #   ProcDef -> [6]: StmtList (body) -> [0]: Call ->
-  #     [1]: StmtList (withConn body) -> [0]: Asgn (result =) ->
+  #   ProcDef -> [6]: StmtList (body) -> [0]: Command ->
+  #     [2]: StmtList (withConnection body) -> [0]: Asgn (result =) ->
   #     [1]: Call (inner findRecords invocation)
-  result[6][0][1][0][1].add(callParams)
-  result[6][0][1][0][1].add(quote do: pagination)
+  result[6][0][2][0][1].add(callParams)
+  result[6][0][2][0][1].add(quote do: pagination)
 
 macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tuple[t: type, fields: seq[string]]]): untyped =
   result = newStmtList()
@@ -621,7 +633,7 @@ macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tup
     # Create proc skeleton
     let procDefAST = quote do:
       proc `procName`*(db: `dbType`): PagedRecords[`modelType`] =
-        db.withConn: result = findRecordsBy(conn, `modelType`)
+        db.withConnection conn: result = findRecordsBy(conn, `modelType`)
 
     var callParams = quote do: @[]
 
@@ -644,11 +656,12 @@ macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tup
 
     result.add procDefAST
 
-proc initPool*(
-    connect: proc(): DbConn,
+proc initPool*[D: DbConnType](
+    connect: proc(): D,
     poolSize = 10,
     hardCap = false,
-    healthCheckQuery = "SELECT 'true' AS alive"): DbConnPool =
+    healthCheckQuery = "SELECT 'true' AS alive"): DbConnPool[D] =
+
   ## Initialize a new DbConnPool. See the `initDb` procedure in the `Example
   ## Fiber ORM Usage`_ for an example
   ##
@@ -666,14 +679,14 @@ proc initPool*(
   ##
   ## .. _Example Fiber ORM Usage: #basic-usage-example-fiber-orm-usage
 
-  initDbConnPool(DbConnPoolConfig(
+  initDbConnPool(DbConnPoolConfig[D](
     connect: connect,
     poolSize: poolSize,
     hardCap: hardCap,
     healthCheckQuery: healthCheckQuery))
 
-template inTransaction*(db: DbConnPool, body: untyped) =
-  pool.withConn(db):
+template inTransaction*(db, body: untyped) =
+  db.withConnection conn:
     conn.exec(sql"BEGIN TRANSACTION")
     try:
       body

src/fiber_orm/db_common.nim

@@ -0,0 +1,3 @@
+import db_connector/[db_postgres, db_sqlite]
+
+type DbConnType* = db_postgres.DbConn or db_sqlite.DbConn

src/fiber_orm/pool.nim

@@ -4,65 +4,62 @@
 
 ## Simple database connection pooling implementation compatible with Fiber ORM.
 
-import std/db_postgres, std/sequtils, std/strutils, std/sugar
+import std/[sequtils, strutils, sugar]
+import db_connector/db_common
 
-import namespaced_logging
+from db_connector/db_sqlite import getRow, close
+from db_connector/db_postgres import getRow, close
 
+import ./db_common as fiber_db_common
 
 type
-  DbConnPoolConfig* = object
-    connect*: () -> DbConn  ## Factory procedure to create a new DBConn
-    poolSize*: int ## The pool capacity.
-    hardCap*: bool ## Is the pool capacity a hard cap?
-                   ##
-                   ## When `false`, the pool can grow beyond the configured
-                   ## capacity, but will release connections down to the its
-                   ## capacity (no less than `poolSize`).
-                   ##
-                   ## When `true` the pool will not create more than its
-                   ## configured capacity.  It a connection is requested, none
-                   ## are free, and the pool is at capacity, this will result
-                   ## in an Error being raised.
+  DbConnPoolConfig*[D: DbConnType] = object
+    connect*: () -> D   ## Factory procedure to create a new DBConn
+    poolSize*: int      ## The pool capacity.
+
+    hardCap*: bool      ## Is the pool capacity a hard cap?
+                        ##
+                        ## When `false`, the pool can grow beyond the
+                        ## configured capacity, but will release connections
+                        ## down to the its capacity (no less than `poolSize`).
+                        ##
+                        ## When `true` the pool will not create more than its
+                        ## configured capacity.  It a connection is requested,
+                        ## none are free, and the pool is at capacity, this
+                        ## will result in an Error being raised.
+
     healthCheckQuery*: string ## Should be a simple and fast SQL query that the
                               ## pool can use to test the liveliness of pooled
                               ## connections.
 
-  PooledDbConn = ref object
-    conn: DbConn
+  PooledDbConn[D: DbConnType] = ref object
+    conn: D
     id: int
     free: bool
 
-  DbConnPool* = ref object
+  DbConnPool*[D: DbConnType] = ref object
     ## Database connection pool
-    conns: seq[PooledDbConn]
-    cfg: DbConnPoolConfig
+    conns: seq[PooledDbConn[D]]
+    cfg: DbConnPoolConfig[D]
     lastId: int
 
-var logNs {.threadvar.}: LoggingNamespace
-
-template log(): untyped =
-  if logNs.isNil: logNs = initLoggingNamespace(name = "fiber_orm/pool", level = lvlNotice)
-  logNs
-
-proc initDbConnPool*(cfg: DbConnPoolConfig): DbConnPool =
-  log().debug("Initializing new pool (size: " & $cfg.poolSize)
-  result = DbConnPool(
+proc initDbConnPool*[D: DbConnType](cfg: DbConnPoolConfig[D]): DbConnPool[D] =
+  result = DbConnPool[D](
     conns: @[],
     cfg: cfg)
 
-proc newConn(pool: DbConnPool): PooledDbConn =
-  log().debug("Creating a new connection to add to the pool.")
+proc newConn[D: DbConnType](pool: DbConnPool[D]): PooledDbConn[D] =
   pool.lastId += 1
-  let conn = pool.cfg.connect()
-  result = PooledDbConn(
-    conn: conn,
-    id: pool.lastId,
-    free: true)
-  pool.conns.add(result)
+  {.gcsafe.}:
+    let conn = pool.cfg.connect()
+    result = PooledDbConn[D](
+      conn: conn,
+      id: pool.lastId,
+      free: true)
+    pool.conns.add(result)
 
-proc maintain(pool: DbConnPool): void =
-  log().debug("Maintaining pool. $# connections." % [$pool.conns.len])
-  pool.conns.keepIf(proc (pc: PooledDbConn): bool =
+proc maintain[D: DbConnType](pool: DbConnPool[D]): void =
+  pool.conns.keepIf(proc (pc: PooledDbConn[D]): bool =
     if not pc.free: return true
 
     try:
@@ -73,9 +70,6 @@ proc maintain(pool: DbConnPool): void =
       except: discard ""
       return false
   )
-  log().debug(
-    "Pruned dead connections. $# connections remaining." %
-    [$pool.conns.len])
 
   let freeConns = pool.conns.filterIt(it.free)
   if pool.conns.len > pool.cfg.poolSize and freeConns.len > 0:
@@ -87,11 +81,8 @@ proc maintain(pool: DbConnPool): void =
       for culled in toCull:
         try: culled.conn.close()
         except: discard ""
-      log().debug(
-        "Trimming pool size. Culled $# free connections. $# connections remaining." %
-        [$toCull.len, $pool.conns.len])
 
-proc take*(pool: DbConnPool): tuple[id: int, conn: DbConn] =
+proc take*[D: DbConnType](pool: DbConnPool[D]): tuple[id: int, conn: D] =
   ## Request a connection from the pool. Returns a DbConn if the pool has free
   ## connections, or if it has the capacity to create a new connection. If the
   ## pool is configured with a hard capacity limit and is out of free
@@ -102,29 +93,22 @@ proc take*(pool: DbConnPool): tuple[id: int, conn: DbConn] =
   pool.maintain
   let freeConns = pool.conns.filterIt(it.free)
 
-  log().debug(
-    "Providing a new connection ($# currently free)." % [$freeConns.len])
-
   let reserved =
     if freeConns.len > 0: freeConns[0]
     else: pool.newConn()
 
   reserved.free = false
-  log().debug("Reserve connection $#" % [$reserved.id])
   return (id: reserved.id, conn: reserved.conn)
 
-proc release*(pool: DbConnPool, connId: int): void =
+proc release*[D: DbConnType](pool: DbConnPool[D], connId: int): void =
   ## Release a connection back to the pool.
-  log().debug("Reclaiming released connaction $#" % [$connId])
   let foundConn = pool.conns.filterIt(it.id == connId)
   if foundConn.len > 0: foundConn[0].free = true
 
-template withConn*(pool: DbConnPool, stmt: untyped): untyped =
+template withConnection*[D: DbConnType](pool: DbConnPool[D], conn, stmt: untyped): untyped =
   ## Convenience template to provide a connection from the pool for use in a
   ## statement block, automatically releasing that connnection when done.
-  ##
-  ## The provided connection is injected as the variable `conn` in the
-  ## statement body.
-  let (connId, conn {.inject.}) = take(pool)
-  try: stmt
-  finally: release(pool, connId)
+  block:
+    let (connId, conn) = take(pool)
+    try: stmt
+    finally: release(pool, connId)

src/fiber_orm/util.nim

@@ -3,12 +3,17 @@
 # Copyright 2019 Jonathan Bernard <jonathan@jdbernard.com>
 
 ## Utility methods used internally by Fiber ORM.
-import json, macros, options, sequtils, strutils, times, unicode,
-  uuids
+import std/[json, macros, options, sequtils, strutils, times, unicode]
+import uuids
 
-import nre except toSeq
+import std/nre except toSeq
 
 type
+  PaginationParams* = object
+    pageSize*: int
+    offset*: int
+    orderBy*: Option[seq[string]]
+
   MutateClauses* = object
     ## Data structure to hold information about the clauses that should be
     ## added to a query. How these clauses are used will depend on the query.
@@ -22,9 +27,11 @@ const ISO_8601_FORMATS = @[
   "yyyy-MM-dd'T'HH:mm:ssz",
   "yyyy-MM-dd'T'HH:mm:sszzz",
   "yyyy-MM-dd'T'HH:mm:ss'.'fffzzz",
+  "yyyy-MM-dd'T'HH:mm:ss'.'ffffzzz",
   "yyyy-MM-dd HH:mm:ssz",
   "yyyy-MM-dd HH:mm:sszzz",
-  "yyyy-MM-dd HH:mm:ss'.'fffzzz"
+  "yyyy-MM-dd HH:mm:ss'.'fffzzz",
+  "yyyy-MM-dd HH:mm:ss'.'ffffzzz"
 ]
 
 proc parseIso8601(val: string): DateTime =
@@ -102,7 +109,7 @@ proc dbFormat*[T](list: seq[T]): string =
 
 proc dbFormat*[T](item: T): string =
   ## For all other types, fall back on a defined `$` function to create a
-  ## string version of the value we can include in an SQL query>
+  ## string version of the value we can include in an SQL query.
   return $item
 
 type DbArrayParseState = enum
@@ -126,18 +133,20 @@ proc parsePGDatetime*(val: string): DateTime =
 
   var correctedVal = val;
 
-  # PostgreSQL will truncate any trailing 0's in the millisecond value leading
-  # to values like `2020-01-01 16:42.3+00`. This cannot currently be parsed by
-  # the standard times format as it expects exactly three digits for
-  # millisecond values. So we have to detect this and pad out the millisecond
-  # value to 3 digits.
-  let PG_PARTIAL_FORMAT_REGEX = re"(\d{4}-\d{2}-\d{2}( |'T')\d{2}:\d{2}:\d{2}\.)(\d{1,2})(\S+)?"
+  # The Nim `times#format` function only recognizes 3-digit millisecond values
+  # but PostgreSQL will sometimes send 1-2 digits, truncating any trailing 0's,
+  # or sometimes provide more than three digits of preceision in the millisecond value leading
+  # to values like `2020-01-01 16:42.3+00` or `2025-01-06 00:56:00.9007+00`.
+  # This cannot currently be parsed by the standard times format as it expects
+  # exactly three digits for millisecond values. So we have to detect this and
+  # coerce the millisecond value to exactly 3 digits.
+  let PG_PARTIAL_FORMAT_REGEX = re"(\d{4}-\d{2}-\d{2}( |'T')\d{2}:\d{2}:\d{2}\.)(\d+)(\S+)?"
   let match = val.match(PG_PARTIAL_FORMAT_REGEX)
 
   if match.isSome:
     let c = match.get.captures
-    if c.toSeq.len == 2: correctedVal = c[0] & alignLeft(c[2], 3, '0')
-    else: correctedVal = c[0] & alignLeft(c[2], 3, '0') & c[3]
+    if c.toSeq.len == 2: correctedVal = c[0] & alignLeft(c[2], 3, '0')[0..2]
+    else: correctedVal = c[0] & alignLeft(c[2], 3, '0')[0..2] & c[3]
 
   var errStr = ""
 
@@ -146,7 +155,7 @@ proc parsePGDatetime*(val: string): DateTime =
     try: return correctedVal.parse(df)
     except: errStr &= "\n\t" & getCurrentExceptionMsg()
 
-  raise newException(ValueError, "Cannot parse PG date. Tried:" & errStr)
+  raise newException(ValueError, "Cannot parse PG date '" & correctedVal & "'. Tried:" & errStr)
 
 proc parseDbArray*(val: string): seq[string] =
   ## Parse a Postgres array column into a Nim seq[string]
@@ -207,21 +216,14 @@ proc parseDbArray*(val: string): seq[string] =
   if not (parseState == inQuote) and curStr.len > 0:
     result.add(curStr)
 
-proc createParseStmt*(t, value: NimNode): NimNode =
+func createParseStmt*(t, value: NimNode): NimNode =
   ## Utility method to create the Nim cod required to parse a value coming from
   ## the a database query. This is used by functions like `rowToModel` to parse
   ## the dataabase columns into the Nim object fields.
 
-  #echo "Creating parse statment for ", t.treeRepr
   if t.typeKind == ntyObject:
 
-    if t.getType == UUID.getType:
-      result = quote do: parseUUID(`value`)
-
-    elif t.getType == DateTime.getType:
-      result = quote do: parsePGDatetime(`value`)
-
-    elif t.getTypeInst == Option.getType:
+    if t.getTypeInst == Option.getType:
       var innerType = t.getTypeImpl[2][0] # start at the first RecList
       # If the value is a non-pointer type, there is another inner RecList
       if innerType.kind == nnkRecList: innerType = innerType[0]
@@ -232,8 +234,28 @@ proc createParseStmt*(t, value: NimNode): NimNode =
         if `value`.len == 0:  none[`innerType`]()
         else:                 some(`parseStmt`)
 
+    elif t.getType == UUID.getType:
+      result = quote do: parseUUID(`value`)
+
+    elif t.getType == DateTime.getType:
+      result = quote do: parsePGDatetime(`value`)
+
     else: error "Unknown value object type: " & $t.getTypeInst
 
+  elif t.typeKind == ntyGenericInst:
+
+    if t.kind == nnkBracketExpr and
+       t.len > 0 and
+       t[0] == Option.getType:
+
+      var innerType = t.getTypeInst[1]
+      let parseStmt = createParseStmt(innerType, value)
+      result = quote do:
+        if `value`.len == 0:  none[`innerType`]()
+        else:                 some(`parseStmt`)
+
+    else: error "Unknown generic instance type: " & $t.getTypeInst
+
   elif t.typeKind == ntyRef:
 
     if $t.getTypeInst == "JsonNode":
@@ -268,28 +290,72 @@ proc createParseStmt*(t, value: NimNode): NimNode =
   else:
     error "Unknown value type: " & $t.typeKind
 
+func fields(t: NimNode): seq[tuple[fieldIdent: NimNode, fieldType: NimNode]] =
+  #[
+  debugEcho "T: " & t.treeRepr
+  debugEcho "T.kind: " & $t.kind
+  debugEcho "T.typeKind: " & $t.typeKind
+  debugEcho "T.GET_TYPE[1]: " & t.getType[1].treeRepr
+  debugEcho "T.GET_TYPE[1].kind: " & $t.getType[1].kind
+  debugEcho "T.GET_TYPE[1].typeKind: " & $t.getType[1].typeKind
+
+  debugEcho "T.GET_TYPE: " & t.getType.treeRepr
+  debugEcho "T.GET_TYPE[1].GET_TYPE: " & t.getType[1].getType.treeRepr
+  ]#
+
+  # Get the object type AST, with base object (if present) and record list.
+  var objDefAst: NimNode
+  if t.typeKind == ntyObject: objDefAst = t.getType
+  elif t.typeKind == ntyTypeDesc:
+    # In this case we have a type AST that is like:
+    # BracketExpr
+    #   Sym "typeDesc"
+    #   Sym "ModelType"
+    objDefAst = t.
+      getType[1].         # get the Sym "ModelType"
+      getType             # get the object definition type
+
+    if objDefAst.kind != nnkObjectTy:
+      error ("unable to enumerate the fields for model type '$#', " &
+        "tried to resolve the type of the provided symbol to an object " &
+        "definition (nnkObjectTy) but got a '$#'.\pAST:\p$#") % [
+          $t, $objDefAst.kind, objDefAst.treeRepr ]
+  else:
+    error ("unable to enumerate the fields for model type '$#', " &
+      "expected a symbol with type ntyTypeDesc but got a '$#'.\pAST:\p$#") % [
+        $t, $t.typeKind, t.treeRepr ]
+
+  # At this point objDefAst should look something like:
+  # ObjectTy
+  #   Empty
+  #   Sym "BaseObject"" | Empty
+  #   RecList
+  #     Sym "field1"
+  #     Sym "field2"
+  #     ...
+
+  if objDefAst[1].kind == nnkSym:
+    # We have a base class symbol, let's recurse and try and resolve the fields
+    # for the base class
+    for fieldDef in objDefAst[1].fields: result.add(fieldDef)
+
+  for fieldDef in objDefAst[2].children:
+    # objDefAst[2] is a RecList of
+    # ignore AST nodes that are not field definitions
+    if fieldDef.kind == nnkIdentDefs: result.add((fieldDef[0], fieldDef[1]))
+    elif fieldDef.kind == nnkSym: result.add((fieldDef, fieldDef.getTypeInst))
+    else: error "unknown object field definition AST: $#" % $fieldDef.kind
+
 template walkFieldDefs*(t: NimNode, body: untyped) =
   ## Iterate over every field of the given Nim object, yielding and defining
   ## `fieldIdent` and `fieldType`, the name of the field as a Nim Ident node
   ## and the type of the field as a Nim Type node respectively.
-  let tTypeImpl = t.getTypeImpl
+  for (fieldIdent {.inject.}, fieldType {.inject.}) in t.fields: body
 
-  var nodeToItr: NimNode
-  if tTypeImpl.typeKind == ntyObject: nodeToItr = tTypeImpl[2]
-  elif tTypeImpl.typeKind == ntyTypeDesc: nodeToItr = tTypeImpl.getType[1].getType[2]
-  else: error $t & " is not an object or type desc (it's a " & $tTypeImpl.typeKind & ")."
-
-  for fieldDef {.inject.} in nodeToItr.children:
-    # ignore AST nodes that are not field definitions
-    if fieldDef.kind == nnkIdentDefs:
-      let fieldIdent {.inject.} = fieldDef[0]
-      let fieldType {.inject.} = fieldDef[1]
-      body
-
-    elif fieldDef.kind == nnkSym:
-      let fieldIdent {.inject.} = fieldDef
-      let fieldType {.inject.} = fieldDef.getType
-      body
+#[ TODO: replace walkFieldDefs with things like this:
+func columnNamesForModel*(modelType: typedesc): seq[string] =
+  modelType.fields.mapIt(identNameToDb($it[0]))
+]#
 
 macro columnNamesForModel*(modelType: typed): seq[string] =
   ## Return the column names corresponding to the the fields of the given
@@ -317,6 +383,7 @@ macro rowToModel*(modelType: typed, row: seq[string]): untyped =
       createParseStmt(fieldType, itemLookup)))
     idx += 1
 
+#[
 macro listFields*(t: typed): untyped =
   var fields: seq[tuple[n: string, t: string]] = @[]
   t.walkFieldDefs:
@@ -324,6 +391,7 @@ macro listFields*(t: typed): untyped =
     else: fields.add((n: $fieldIdent, t: $fieldType))
 
   result = newLit(fields)
+]#
 
 proc typeOfColumn*(modelType: NimNode, colName: string): NimNode =
   ## Given a model type and a column name, return the Nim type for that column.
@@ -370,8 +438,8 @@ macro populateMutateClauses*(t: typed, newRecord: bool, mc: var MutateClauses):
 
       # if we're looking at an optional field, add logic to check for presence
       elif fieldType.kind == nnkBracketExpr and
-         fieldType.len > 0 and
-         fieldType[0] == Option.getType:
+           fieldType.len > 0 and
+           fieldType[0] == Option.getType:
 
         result.add quote do:
           `mc`.columns.add(identNameToDb(`fieldName`))
@@ -388,6 +456,19 @@ macro populateMutateClauses*(t: typed, newRecord: bool, mc: var MutateClauses):
           `mc`.placeholders.add("?")
           `mc`.values.add(dbFormat(`t`.`fieldIdent`))
 
+
+proc getPagingClause*(page: PaginationParams): string =
+  ## Given a `PaginationParams` object, return the SQL clause necessary to
+  ## limit the number of records returned by a query.
+  result = ""
+  if page.orderBy.isSome:
+    let orderByClause = page.orderBy.get.map(identNameToDb).join(",")
+    result &= " ORDER BY " & orderByClause
+  else:
+    result &= " ORDER BY id"
+
+  result &= " LIMIT " & $page.pageSize & " OFFSET " & $page.offset
+
 ## .. _model class: ../fiber_orm.html#objectminusrelational-modeling-model-class
 ## .. _rules for name mapping: ../fiber_orm.html
 ## .. _table name: ../fiber_orm.html