Add option to return err when values don't exist in multiGet (#94)

Author: bhartnett

rocksdb/columnfamily.nim

@@ -82,9 +82,10 @@ template multiGet*(
     cf: ColFamilyReadOnly | ColFamilyReadWrite,
     keys: openArray[seq[byte]],
     sortedInput = false,
+    errorOnValueNotExists = true,
 ): RocksDBResult[seq[seq[byte]]] =
   ## Get a batch of values for the given set of keys.
-  cf.db.multiGet(keys, sortedInput, cf.handle)
+  cf.db.multiGet(keys, sortedInput, errorOnValueNotExists, cf.handle)
 
 template put*(cf: ColFamilyReadWrite, key, val: openArray[byte]): RocksDBResult[void] =
   ## Puts a value for the given key into the column family.

rocksdb/rocksdb.nim

@@ -269,23 +269,24 @@ proc get*(
     db: RocksDbRef, key: openArray[byte], cfHandle = db.defaultCfHandle
 ): RocksDBResult[seq[byte]] =
   ## Get the value for the given key from the specified column family.
-  ## If the value does not exist, an empty error will be returned in the result.
+  ## If the value does not exist, an error will be returned in the result.
   ## If the value does exist, the value will be returned in the result.
 
-  var dataRes: RocksDBResult[seq[byte]]
+  var value: seq[byte]
   proc onData(data: openArray[byte]) =
-    dataRes.ok(@data)
+    value = @data
 
-  let res = db.get(key, onData, cfHandle)
-  if res.isOk():
-    return dataRes
-
-  dataRes.err(res.error())
+  let valueExists = ?db.get(key, onData, cfHandle)
+  if valueExists:
+    ok(value)
+  else:
+    err("rocksdb: value does not exist")
 
 proc multiGet*(
     db: RocksDbRef,
     keys: openArray[seq[byte]],
     sortedInput = false,
+    errorOnValueNotExists = true,
     cfHandle = db.defaultCfHandle,
 ): RocksDBResult[seq[seq[byte]]] =
   ## Get a batch of values for the given set of keys.
@@ -304,11 +305,11 @@ proc multiGet*(
   assert keys.len() > 0
 
   var
-    keysList = keys.mapIt(cast[cstring](it[0].addr))
+    keysList = keys.mapIt(cast[cstring](it.unsafeAddrOrNil()))
     keysListSizes = keys.mapIt(csize_t(it.len))
     errors = newSeq[cstring](keys.len())
 
-  var values =
+  var valuesPtrs =
     when NimMajor >= 2 and NimMinor >= 2:
       newSeqUninit[ptr rocksdb_pinnableslice_t](keys.len)
     else:
@@ -321,7 +322,7 @@ proc multiGet*(
     csize_t(keys.len),
     cast[cstringArray](keysList[0].addr),
     keysListSizes[0].addr,
-    values[0].addr,
+    valuesPtrs[0].addr,
     cast[cstringArray](errors[0].addr),
     sortedInput,
   )
@@ -332,8 +333,14 @@ proc multiGet*(
       rocksdb_free(e)
       return res
 
-  var data = newSeq[seq[byte]](keys.len())
-  for i, v in values:
+  var values = newSeq[seq[byte]](keys.len())
+  for i, v in valuesPtrs:
+    if v.isNil():
+      if errorOnValueNotExists:
+        return err("rocksdb: value does not exist at index " & $i)
+      else:
+        continue
+
     var vLen: csize_t
     let src = rocksdb_pinnableslice_value(v, vLen.addr)
 
@@ -344,11 +351,11 @@ proc multiGet*(
         else:
           newSeq[byte](vLen.int)
       copyMem(dest[0].addr, src, vLen)
-      data[i] = dest
+      values[i] = dest
 
     rocksdb_pinnableslice_destroy(v)
 
-  ok(data)
+  ok(values)
 
 proc put*(
     db: RocksDbReadWriteRef, key, val: openArray[byte], cfHandle = db.defaultCfHandle

tests/test_columnfamily.nim

@@ -53,8 +53,7 @@ suite "ColFamily Tests":
     check r1.isOk() and r1.value == val
 
     var r2 = cf.get(otherKey)
-    # there's no error string for missing keys
-    check r2.isOk() == false and r2.error.len == 0
+    check r2.isErr() and r2.error.len > 0
 
     var e1 = cf.keyExists(key)
     check e1.isOk() and e1.value == true
@@ -132,14 +131,15 @@ suite "ColFamily Tests":
     let
       keyValue1 = @[100.byte]
       keyValue2 = @[300.byte]
-      keyValue3 = @[200.byte]
+      keyValue3 = default(seq[byte])
 
     check:
       cf.put(keyValue1, keyValue1).isOk()
       cf.put(keyValue2, keyValue2).isOk()
+      cf.put(keyValue3, keyValue3).isOk()
       cf.keyExists(keyValue1).get() == true
       cf.keyExists(keyValue2).get() == true
-      cf.keyExists(keyValue3).get() == false
+      cf.keyExists(keyValue3).get() == true
 
     let dataRes = cf.multiGet(@[keyValue1, keyValue2, keyValue3]).expect("ok")
     check:

tests/test_rocksdb.nim

@@ -52,8 +52,7 @@ suite "RocksDbRef Tests":
     check r1.isOk() and r1.value == val
 
     var r2 = db.get(otherKey)
-    # there's no error string for missing keys
-    check r2.isOk() == false and r2.error.len == 0
+    check r2.isErr() and r2.error.len > 0
 
     var e1 = db.keyExists(key)
     check e1.isOk() and e1.value == true
@@ -109,8 +108,7 @@ suite "RocksDbRef Tests":
     check r1.isOk() and r1.value == val
 
     var r2 = db.get(otherKey)
-    # there's no error string for missing keys
-    check r2.isOk() == false and r2.error.len == 0
+    check r2.isErr() and r2.error.len > 0
 
     var e1 = db.keyExists(key, defaultCfHandle)
     check e1.isOk() and e1.value == true
@@ -586,23 +584,30 @@ suite "RocksDbRef Tests":
         dataRes[1] == keyValue2
 
     block:
-      let dataRes = db.multiGet(@[keyValue2, keyValue3]).expect("ok")
+      let dataRes =
+        db.multiGet(@[keyValue2, keyValue3], errorOnValueNotExists = false).expect("ok")
       check:
         dataRes.len() == 2
         dataRes[0] == keyValue2
         dataRes[1] == default(seq[byte])
 
     block:
-      let dataRes = db.multiGet(@[keyValue1, keyValue2, keyValue3]).expect("ok")
+      let
+        res1 = db.multiGet(@[keyValue1, keyValue2, keyValue3])
+        res2 =
+          db.multiGet(@[keyValue1, keyValue2, keyValue3], errorOnValueNotExists = true)
       check:
-        dataRes.len() == 3
-        dataRes[0] == keyValue1
-        dataRes[1] == keyValue2
-        dataRes[2] == default(seq[byte])
+        res1.isErr()
+        res2.isErr()
 
     block:
-      let dataRes =
-        db.multiGet(@[keyValue1, keyValue2, keyValue3], sortedInput = true).expect("ok")
+      let dataRes = db
+        .multiGet(
+          @[keyValue1, keyValue2, keyValue3],
+          sortedInput = true,
+          errorOnValueNotExists = false,
+        )
+        .expect("ok")
       check:
         dataRes.len() == 3
         dataRes[0] == keyValue1
@@ -616,7 +621,7 @@ suite "RocksDbRef Tests":
             keyValue1, keyValue2, keyValue3, keyValue4, keyValue5, keyValue6, keyValue7,
             keyValue8, keyValue9,
           ]
-        dataRes = db.multiGet(keys).expect("ok")
+        dataRes = db.multiGet(keys, errorOnValueNotExists = false).expect("ok")
       check:
         dataRes.len() == 9
         dataRes[0] == keyValue1