F# 查询异常，"unrecognized method call value"

Question

问：下面的异常是什么意思？

System.Exception: 'unrecognised method call value(FSharp.Data.Sql.Runtime.QueryImplementation+SqlQueryable`1[FSharp.Data.Sql.Common.SqlEntity]).GroupJoin(value(FSharp.Data.Sql.Runtime.QueryImplementation+SqlQueryable`1[FSharp.Data.Sql.Common.SqlEntity]), arClientRow => arClientRow.GetColumn("CLIENT_ID"), dsItemRow => dsItemRow.GetColumn("CLIENT_ID"), (arClientRow, dsItemGroup) => new AnonymousObject`2(Item1 = arClientRow, Item2 = dsItemGroup.DefaultIfEmpty()))'

我正在尝试将 Pervasive SQL 查询转换为使用 SqlDataProvider 和 ODBC 连接的 F# 查询，一点一点地慢慢构建。我在以下查询中遇到了一个异常，其中有一个有点神秘的异常。

let Q2KQuery = query {
    for arClientRow in Q2KDb.Dbo.ArClient do
    leftOuterJoin dsItemRow in Q2KDb.Dbo.DsItem 
        on (arClientRow.ClientId = dsItemRow.ClientId) 
        into dsItemGroup
    select (arClientRow, dsItemGroup) (*select statement simplified here for demonstration purposes*)
}

printfn "%i" (Seq.length Q2KQuery)

当执行printfn语句并实际计算表达式时，异常命中：

System.Exception: 'unrecognised method call value(FSharp.Data.Sql.Runtime.QueryImplementation+SqlQueryable`1[FSharp.Data.Sql.Common.SqlEntity]).GroupJoin(value(FSharp.Data.Sql.Runtime.QueryImplementation+SqlQueryable`1[FSharp.Data.Sql.Common.SqlEntity]), arClientRow => arClientRow.GetColumn("CLIENT_ID"), dsItemRow => dsItemRow.GetColumn("CLIENT_ID"), (arClientRow, dsItemGroup) => new AnonymousObject`2(Item1 = arClientRow, Item2 = dsItemGroup.DefaultIfEmpty()))'

这是一个更大的查询的全部部分，它在执行时有完全相同的异常：

let Q2KQuery = query {
    for arClientRow in Q2KDb.Dbo.ArClient do
    leftOuterJoin dsItemRow in Q2KDb.Dbo.DsItem 
        on (arClientRow.ClientId = dsItemRow.ClientId) 
        into dsItemGroup
    for dsItemRow in dsItemGroup do
    leftOuterJoin dsWhseInvHeaderRow in Q2KDb.Dbo.DsWhseInvHeader
        on ((dsItemRow.ClientId, dsItemRow.ItemId) = (dsWhseInvHeaderRow.ClientId, dsWhseInvHeaderRow.ItemId))
        into dsWhseInvHeaderGroup
    for dsWhseInvHeaderRow in dsWhseInvHeaderGroup do
    where (
        dsItemRow.ObsoleteFlg <> "Y"
        && arClientRow.IsInactive <> "Y"
        && dsWhseInvHeaderRow.WhseId = "B1"
        && dsItemRow.InvunitQty = 1
    )
    select (arClientRow, dsItemRow, dsWhseInvHeaderRow) (*select statement simplified here for demonstration purposes*)
}

仅供参考，从中翻译此 F# 查询的 SQL 查询如下（SELECT 语句不如引发 F# 异常的 JOIN 子句重要):

SELECT
-- LOTS of selects here... --
-- ... --
----- the important part of the F# queries begin here -----
FROM 
    ArClient
    LEFT JOIN DsItem 
    ON ArClient.CLIENT_ID = DsItem.CLIENT_ID
    LEFT JOIN DsWhse_Inv_Header 
    ON (DsItem.CLIENT_ID = DsWhse_Inv_Header.CLIENT_ID)
    AND (DsItem.ITEM_ID = DsWhse_Inv_Header.ITEM_ID)
WHERE (
    ((DsItem.OBSOLETE_FLG) <> 'Y')
    AND ((ArClient.IS_INACTIVE) <> 'Y')
    AND ((DsWhse_Inv_Header.WHSE_ID) = 'B1')
    AND ((DsItem.INVUNIT_QTY) = 1)
    )
ORDER BY
    CONCAT(LEFT(DsItem.CLIENT_ID, 4), RTRIM(LTRIM(DsItem.ITEM_ID)));

Answer 1

阅读了一些 SO 答案和 GitHub 问题（链接如下）后，似乎不支持按照我的方式对这种 SQL 数据库进行确切的操作目前（也许吧？至少据我所知是这样），尽管 !! 运算符显然可以在 query 表达式中加入左连接——但到目前为止我还没有成功.

我有但是发现以下笨拙的解决方法使用我一直使用的相同 query 表达式通过将数据转换为强制将数据读入内存一个 List（或 Array，等等）首先：

let ArClient = Seq.toList <| query {
    for row in Q2KDb.Dbo.ArClient do
    where (row.IsInactive <> "Y")
    select row
}

let DsItem = Seq.toList <| query {
    for row in Q2KDb.Dbo.DsItem do
    where (row.ObsoleteFlg <> "Y" && row.InvunitQty = 1)
    select row
}

let DsWhseInvHeader = Seq.toList <| query {
    for row in Q2KDb.Dbo.DsWhseInvHeader do
    where (row.WhseId = "B1")
    select row
}

然后可以在原始 query 表达式中使用，只需进行最小的更改。

let results = Seq.toList <| query {
    for arClientRow in ArClient do
    leftOuterJoin dsItemRow in DsItem
        on (arClientRow.ClientId = dsItemRow.ClientId) 
        into dsItemGroup
    for dsItemRow in dsItemGroup do
    leftOuterJoin dsWhseInvHeaderRow in DsWhseInvHeader
        on ((dsItemRow.ClientId, dsItemRow.ItemId) = (dsWhseInvHeaderRow.ClientId, dsWhseInvHeaderRow.ItemId))
        into dsWhseInvHeaderGroup
    for dsWhseInvHeaderRow in dsWhseInvHeaderGroup do
    select (arClientRow (*etc etc*))

这当然是非常低效的（读取 DsItem 的 62k+ 行使用大约 500MB+ 的内存并且需要 30+ 秒来读取），但它 实际上 工作...

链接：

GitHub: "unrecognised method call value" on a left outer join #588

GitHub: Ordering of joins can cause runtime exception with (!!) #614

GitHub: leftOuterJoin causing "unrecognized method call" with Postgresql #235

F# 查询异常，"unrecognized method call value"

F# Query Exception, "unrecognized method call value"

.net

sql

f#

exception

pervasive