Add basic tuple and value fetching from queries.

Add safeties for =destroy hooks.

FossilOrigin-Name: 2fae5297a0d0598cc3580777688b4f4307de008d4f379d2fb224c8a74cb9b708

src/kuzu.nim

@@ -13,14 +13,18 @@ else:
     include "kuzu/0.8.2.nim"
 
 import
-    std/strformat
+    std/strformat,
+    std/strutils
 
+# Order very much matters here pre Nim 3.0 multi-pass compiling.
 include
     "kuzu/constants.nim",
     "kuzu/types.nim",
     "kuzu/config.nim",
     "kuzu/database.nim",
     "kuzu/connection.nim",
+    "kuzu/value.nim",
+    "kuzu/tuple.nim",
     "kuzu/queries.nim"
 
 

src/kuzu/connection.nim

@@ -2,14 +2,16 @@
 
 proc `=destroy`*( conn: KuzuConnectionObj ) =
     ## Graceful cleanup for open connection handles.
+    if conn.valid:
         kuzu_connection_destroy( addr conn.handle )
 
 
-proc connect*( db: KuzuDB ): KuzuConnection =
+proc connect*( db: KuzuDatabase ): KuzuConnection =
     ## Connect to a database.
     result = new KuzuConnection
-    var rv = kuzu_connection_init( addr db.handle, addr result.handle )
+    if kuzu_connection_init( addr db.handle, addr result.handle ) == KuzuSuccess:
-    if rv != KuzuSuccess:
+        result.valid = true
+    else:
         raise newException( KuzuException, "Unable to connect to the database." )
 
 

src/kuzu/database.nim

@@ -1,21 +1,23 @@
 # vim: set et sta sw=4 ts=4 :
 
-proc `=destroy`*( db: KuzuDBObj ) =
+proc `=destroy`*( db: KuzuDatabaseObj ) =
     ## Graceful cleanup for an open DB handle when it goes out of scope.
+    if db.valid:
         kuzu_database_destroy( addr db.handle )
 
 
-proc newKuzuDatabase*( path="", config=kuzuConfig() ): KuzuDB =
+proc newKuzuDatabase*( path="", config=kuzuConfig() ): KuzuDatabase =
     ## Create a new Kuzu database handle.  Creates an in-memory
     ## database by default, but writes to disk if a +path+ is supplied.
 
-    result        = new KuzuDB
+    result        = new KuzuDatabase
     result.config = config
     result.path   = if path != "" and path != ":memory:": path else: "(in-memory)"
     result.handle = kuzu_database()
 
-    var rv = kuzu_database_init( path, config, addr result.handle )
+    if kuzu_database_init( path, config, addr result.handle ) == KuzuSuccess:
-    if rv != KuzuSuccess:
+        result.valid = true
+    else:
         raise newException( KuzuException, "Unable to open database." )
 
 

src/kuzu/queries.nim

@@ -2,6 +2,7 @@
 
 proc `=destroy`*( query: KuzuQueryResultObj ) =
     ## Graceful cleanup for out of scope query objects.
+    if query.valid:
         kuzu_query_result_destroy( addr query.handle )
         kuzu_query_summary_destroy( addr query.summary )
 
@@ -9,15 +10,39 @@ proc `=destroy`*( query: KuzuQueryResultObj ) =
 proc query*( conn: KuzuConnection, query: string ): KuzuQueryResult =
     ## Perform a database +query+ and return the result.
     result = new KuzuQueryResult
-    var rv = kuzu_connection_query( addr conn.handle, query, addr result.handle )
+    if kuzu_connection_query( addr conn.handle, query, addr result.handle ) == KuzuSuccess:
-    if rv == KuzuSuccess:
         discard kuzu_query_result_get_query_summary( addr result.handle, addr result.summary )
         result.num_columns    = kuzu_query_result_get_num_columns( addr result.handle )
         result.num_tuples     = kuzu_query_result_get_num_tuples( addr result.handle )
         result.compile_time   = kuzu_query_summary_get_compiling_time( addr result.summary )
         result.execution_time = kuzu_query_summary_get_execution_time( addr result.summary )
+        result.valid          = true
     else:
         var err = kuzu_query_result_get_error_message( addr result.handle )
         raise newException( KuzuQueryException, &"Error running query: {err}" )
 
 
+proc `$`*( query: KuzuQueryResult ): string =
+    ## Return the entire result set as a string.
+    result = $kuzu_query_result_to_string( addr query.handle )
+
+
+proc hasNext*( query: KuzuQueryResult ): bool =
+    ## Returns +true+ if there are more tuples to be consumed.
+    result = kuzu_query_result_has_next( addr query.handle )
+
+
+proc getNext*( query: KuzuQueryResult ): KuzuFlatTuple =
+    result = new KuzuFlatTuple
+    if kuzu_query_result_get_next( addr query.handle, addr result.handle ) == KuzuSuccess:
+        result.valid = true
+        result.num_columns = query.num_columns
+    else:
+        raise newException( KuzuQueryException, &"Unable to fetch next tuple." )
+
+
+iterator items*( query: KuzuQueryResult ): KuzuFlatTuple =
+    ## Iterate available tuples, yielding to the block.
+    while query.hasNext:
+        yield query.getNext
+

src/kuzu/tuple.nim

@@ -0,0 +1,23 @@
+# vim: set et sta sw=4 ts=4 :
+
+proc `=destroy`*( tpl: KuzuFlatTupleObj ) =
+    ## Graceful cleanup for out of scope tuples.
+    if tpl.valid:
+        kuzu_flat_tuple_destroy( addr tpl.handle )
+
+
+proc `$`*( tpl: KuzuFlatTuple ): string =
+    ## Stringify a tuple.
+    result = $kuzu_flat_tuple_to_string( addr tpl.handle )
+    result.removeSuffix( "\n" )
+
+
+proc `[]`*( tpl: KuzuFlatTuple, idx: int ): KuzuValue =
+    ## Returns a KuzuValue at the given +idx+.
+    result = new KuzuValue
+    if kuzu_flat_tuple_get_value( addr tpl.handle, idx.uint64, addr result.handle ) == KuzuSuccess:
+        result.valid = true
+    else:
+        raise newException( KuzuIndexException,
+            &"Unable to fetch tuple value at idx {idx}. ({tpl.num_columns} column(s).)" )
+

src/kuzu/types.nim

@@ -1,14 +1,16 @@
 # vim: set et sta sw=4 ts=4 :
 
 type
-    KuzuDBObj = object
+    KuzuDatabaseObj = object
         handle*: kuzu_database
         path*: string
         config*: kuzu_system_config
-    KuzuDB* = ref KuzuDBObj
+        valid = false
+    KuzuDatabase* = ref KuzuDatabaseObj
 
     KuzuConnectionObj = object
         handle*: kuzu_connection
+        valid = false
     KuzuConnection* = ref KuzuConnectionObj
 
     KuzuQueryResultObj = object
@@ -18,8 +20,21 @@ type
         num_tuples*:     uint64 = 0
         compile_time*:   cdouble = 0
         execution_time*: cdouble = 0
+        valid = false
     KuzuQueryResult* = ref KuzuQueryResultObj
 
+    KuzuFlatTupleObj = object
+        handle*:     kuzu_flat_tuple
+        num_columns: uint64 = 0
+        valid = false
+    KuzuFlatTuple* = ref KuzuFlatTupleObj
+
+    KuzuValueObj = object
+        handle*: kuzu_value
+        valid = false
+    KuzuValue* = ref KuzuValueObj
+
     KuzuException* = object of CatchableError
     KuzuQueryException* = object of KuzuException
+    KuzuIndexException* = object of KuzuException
 

src/kuzu/value.nim

@@ -0,0 +1,13 @@
+# vim: set et sta sw=4 ts=4 :
+
+proc `=destroy`*( value: KuzuValueObj ) =
+    ## Graceful cleanup for out of scope values.
+    if value.valid:
+        kuzu_value_destroy( addr value.handle )
+
+
+proc `$`*( value: KuzuValue ): string =
+    ## Stringify a value.
+    result = $kuzu_value_to_string( addr value.handle )
+
+

tests/queries/t_can_iterate_tuples.nim

@@ -0,0 +1,19 @@
+# vim: set et sta sw=4 ts=4 :
+
+discard """
+output: "Camel\nLampshade\nDelicious Cake\n"
+"""
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+
+for thing in @[ "Camel", "Lampshade", "Delicious Cake" ]:
+    q = conn.query( "CREATE (d:Doop {thing: '" & thing & "'})" )
+
+for tpl in conn.query( "MATCH (d:Doop) RETURN d.thing" ):
+    echo $tpl
+

tests/queries/t_can_stringify_results.nim

@@ -0,0 +1,17 @@
+# vim: set et sta sw=4 ts=4 :
+
+discard """
+output: "d.thing\nokay!\n\n"
+"""
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+
+echo $q
+

tests/queries/t_knows_if_there_are_waiting_tuples.nim

@@ -0,0 +1,24 @@
+# vim: set et sta sw=4 ts=4 :
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+assert typeOf( q ) is KuzuQueryResult
+
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+assert q.num_tuples == 0
+assert q.hasNext == false
+
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+assert q.num_tuples == 1
+assert q.hasNext == true
+
+discard $q  # consume the tuple result
+
+assert q.num_tuples == 1
+assert q.hasNext == false
+

tests/tuples/t_can_be_stringified.nim

@@ -0,0 +1,19 @@
+# vim: set et sta sw=4 ts=4 :
+
+discard """
+output: "okay!"
+"""
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+
+var tup = q.getNext
+
+echo $tup
+

tests/tuples/t_throws_exception_fetching_at_end.nim

@@ -0,0 +1,17 @@
+# vim: set et sta sw=4 ts=4 :
+
+import
+    std/re
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+
+try:
+   discard q.getNext
+except KuzuQueryException as err:
+    assert err.msg.contains( re"""Unable to fetch next tuple.""" )
+

tests/tuples/t_throws_exception_invalid_index.nim

@@ -0,0 +1,20 @@
+# vim: set et sta sw=4 ts=4 :
+
+import
+    std/re
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+
+let tup = q.getNext
+
+try:
+    echo tup[22]
+except KuzuIndexException as err:
+    assert err.msg.contains( re"""Unable to fetch tuple value at idx 22.""" )
+

tests/values/t_can_be_stringified.nim

@@ -0,0 +1,20 @@
+# vim: set et sta sw=4 ts=4 :
+
+discard """
+output: "okay!"
+"""
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+
+var tup = q.getNext
+var val = tup[0]
+
+echo $val
+