Merge pull request 'multi-result-sets' (#1) from multi-result-sets into main

.gitignore

@@ -6,4 +6,5 @@ kuzu
 nimcache/*
 tests/*
 testresults/*
+testresults.html
 

History.md

@@ -1,5 +1,19 @@
 # Release History for nim-kuzu
 
+---
+## v0.6.0 [2025-07-17] Mahlon E. Smith <mahlon@martini.nu>
+
+Enhancement:
+
+- Provide functions for retreiving multiple result sets from a
+  single primary query object.
+
+
+Minutiae:
+
+- Add a KuzuInterationError, to disambiguate iteration errors from
+  IndexErrors.
+
 ---
 ## v0.5.0 [2025-07-13] Mahlon E. Smith <mahlon@martini.nu>
 
@@ -34,4 +48,3 @@ so update version to reflect the 0.9.0 release.
 ## v0.1.0 [2025-03-31] Mahlon E. Smith <mahlon@martini.nu>
 
 Initial public release.
-

USAGE.md

@@ -308,13 +308,13 @@ for pair in res.column_names.zip( res.column_types ):
   # ("e.activity", KUZU_TIMESTAMP)
 ```
 
-## Reading Result Sets
+## Reading Results
 
 So far we've just been showing values by converting the entire `KuzuQueryResult`
 to a string.  Convenient for quick examples and debugging, but not much else.
 
 A `KuzuQueryResult` is an iterator. You can use regular Nim functions that yield
-each `KuzuFlatTuple` -- essentially, each row that was returned in the set.
+each `KuzuFlatTuple` -- essentially, each row that was returned in a result set.
 
 ```nim
 var res = conn.query """
@@ -350,12 +350,52 @@ if res.hasNext:
 
 echo res.getNext #=> 2
 echo res.getNext #=> 3
-echo res.getNext #=> KuzuIndexError exception!
+echo res.getNext #=> KuzuIterationError exception!
 ```
 
 Manually rewind the `KuzuQueryResult` via `rewind()`.
 
 
+## Multiple Query Results
+
+A query can potentially return any number of separate statements.  Iterate over
+linked `KuzuQueryResult` objects with the `sets()` iterator.
+
+```nim
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+let query = conn.query """
+  UNWIND [1,2,3] as items
+  RETURN items;
+
+  UNWIND [4,5,6] as items
+  RETURN items;
+
+  UNWIND [7,8,9] as items
+  RETURN items;
+"""
+
+for row in query:
+  echo row
+  # 1
+  # 2
+  # 3
+
+for set in query.sets:
+  for row in set:
+    echo row
+    # 4
+    # 5
+    # 6
+    # 7
+    # 8
+    # 9
+```
+
+
 ## Working with Values
 
 A `KuzuFlatTuple` contains the entire row.  You can index a value at its column

experiments/imdb/imdb_find_actor_path.nim

@@ -19,7 +19,7 @@ import
     std/strformat
 import kuzu
 
-const DB = "imdb"
+const DB = "imdb.kz"
 const DOT = "imdb-results.dot"
 
 if not DB.fileExists:
@@ -37,7 +37,7 @@ var res:  KuzuQueryResult
 var fromActor = paramStr(1)
 var toActor   = paramStr(2)
 
-var db = newKuzuDatabase( "imdb", kuzuConfig(read_only=true) )
+var db = newKuzuDatabase( DB, kuzuConfig(read_only=true) )
 var conn = db.connect
 
 echo "Database opened: ", db.path

experiments/imdb/imdb_import.nim

@@ -20,7 +20,7 @@ import
     zip/gzipfiles,
     kuzu
 
-const DB     = "imdb"
+const DB     = "imdb.kz"
 const SOURCE = "https://datasets.imdbws.com"
 const FILES  = @[ "name.basics", "title.basics", "title.principals" ]
 

kuzu.nimble

@@ -1,6 +1,6 @@
 # vim: set et sta sw=4 ts=4 :
 
-version     = "0.5.0"
+version     = "0.6.0"
 author      = "Mahlon E. Smith"
 description = "Kuzu is an embedded graph database built for query speed and scalability."
 license     = "BSD-3-Clause"

src/kuzu/constants.nim

@@ -1,6 +1,6 @@
 # vim: set et sta sw=4 ts=4 :
 
-const KUZU_VERSION*             = "0.5.0"
+const KUZU_VERSION*             = "0.6.0"
 const KUZU_EXPECTED_LIBVERSION* = "0.11.0"
 const BLOB_MAXSIZE = 4096
 

src/kuzu/queries.nim

@@ -147,14 +147,14 @@ func hasNext*( query: KuzuQueryResult ): bool =
 
 
 func getNext*( query: KuzuQueryResult ): KuzuFlatTuple =
-    ## Consume and return the next tuple result, or raise a KuzuIndexError
+    ## Consume and return the next tuple result, or raise a KuzuIterationError
-    ## if at the end of the result set.
+    ## if at the end of the result tuples.
     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( KuzuIndexError, &"Query iteration past end." )
+        raise newException( KuzuIterationError, &"Query iteration past end of tuples." )
 
 
 func rewind*( query: KuzuQueryResult ) =
@@ -162,6 +162,32 @@ func rewind*( query: KuzuQueryResult ) =
     kuzu_query_result_reset_iterator( addr query.handle )
 
 
+func hasNextSet*( query: KuzuQueryResult ): bool =
+    ## Returns +true+ if there are more result sets to be consumed.
+    result = kuzu_query_result_has_next_query_result( addr query.handle )
+
+
+# Keeping this private, because it's only safe to call from within
+# an iterator -- overwriting a query variable with the next result
+# goes boom.
+func getNextSet( query: KuzuQueryResult ): KuzuQueryResult =
+    ## Consume and return the next query set result, or raise a KuzuIterationError
+    ## if at the end of sets.
+    result = new KuzuQueryResult
+    if kuzu_query_result_get_next_query_result( addr query.handle, addr result.handle ) == KuzuSuccess:
+        result.valid = true
+        result.getQueryMetadata()
+    else:
+        raise newException( KuzuIterationError, &"Query iteration past end of set." )
+
+
+iterator sets*( query: KuzuQueryResult ): KuzuQueryResult =
+    ## Iterate available query result sets, yielding to the block.
+    while query.hasNextSet:
+        yield query.getNextSet
+    # NOTE: There is no 'rewind' mechanism for result sets.
+
+
 iterator items*( query: KuzuQueryResult ): KuzuFlatTuple =
     ## Iterate available tuples, yielding to the block.
     while query.hasNext:

src/kuzu/types.nim

@@ -51,5 +51,6 @@ type
     KuzuException*      = object of CatchableError
     KuzuQueryError*     = object of KuzuException
     KuzuIndexError*     = object of KuzuException
+    KuzuIterationError* = object of KuzuException
     KuzuTypeError*      = object of KuzuException
 

tests/queries/t_can_contain_multiple_result_sets.nim

@@ -0,0 +1,42 @@
+# vim: set et sta sw=4 ts=4 :
+
+discard """
+output: "Jenny|Lenny\nLenny\nJenny\n"
+"""
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query """
+CREATE NODE TABLE User(
+    id SERIAL PRIMARY KEY,
+    name STRING
+);
+
+CREATE REL TABLE FOLLOWS(
+   From User To User
+);
+
+MERGE (a:User {name: "Lenny"})-[f:Follows]->(b:User {name: "Jenny"});
+"""
+
+q = conn.query( "MATCH (u:User) RETURN *" )
+
+assert typeOf( q ) is KuzuQueryResult
+assert q.hasNextSet == false
+
+q = conn.query """
+    MATCH (a:User)<-[f:Follows]-(b:User) RETURN a.name, b.name;
+    MATCH (u:User) RETURN u.name;
+"""
+
+assert typeOf( q ) is KuzuQueryResult
+assert q.hasNextSet == true
+
+echo q.getNext
+for query_result in q.sets:
+    for row in query_result.items:
+        echo row
+

tests/tuples/t_throws_exception_fetching_at_end.nim

@@ -12,6 +12,6 @@ q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
 
 try:
    discard q.getNext
-except KuzuIndexError as err:
+except KuzuIterationError as err:
     assert err.msg.contains( re"""Query iteration past end.""" )