Fix nested transactions and update SQLite_jll (#341)

- Add `intransaction(db)` helper to detect if already in a transaction
- Fix `transaction()` to use savepoints when nested and skip PRAGMA
  statements that cannot run inside transactions
- Update SQLite_jll compat to 3.51
- Add test for issue #341 (load! inside transaction)

Fixes #341

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: quinnj

Project.toml

@@ -1,6 +1,6 @@
 name = "SQLite"
 uuid = "0aa819cd-b072-5ff4-a722-6bc24af294d9"
-version = "1.7.0"
+version = "1.7.1"
 authors = ["Jacob Quinn <quinn.jacobd@gmail.com>", "JuliaData Contributors"]
 
 [deps]
@@ -13,7 +13,7 @@ WeakRefStrings = "ea10d353-3f73-51f8-a26c-33c1cb351aa5"
 
 [compat]
 DBInterface = "2.5"
-SQLite_jll = "3"
+SQLite_jll = "3.51"
 Tables = "1"
 WeakRefStrings = "0.4,0.5,0.6,1"
 julia = "1.9"

src/SQLite.jl

@@ -82,6 +82,14 @@ Base.close(db::DB) = _close_db!(db)
 Base.isopen(db::DB) = isopen(db.handle)
 Base.isopen(handle::DBHandle) = handle != C_NULL
 
+"""
+    SQLite.intransaction(db::DB) -> Bool
+
+Check if the database connection is currently in a transaction.
+Returns `true` if in a transaction, `false` if in autocommit mode.
+"""
+intransaction(db::DB) = C.sqlite3_get_autocommit(db.handle) == 0
+
 function finalize_statements!(db::DB)
     # close stmts
     for stmt_wrapper in keys(db.stmt_wrappers)
@@ -650,9 +658,16 @@ In the second method, `func` is executed within a transaction (the transaction b
 function transaction end
 
 function transaction(db::DB, mode = "DEFERRED")
-    execute(db, "PRAGMA temp_store=MEMORY;")
+    already_in_transaction = intransaction(db)
+    # PRAGMA statements cannot be executed inside a transaction
+    already_in_transaction || execute(db, "PRAGMA temp_store=MEMORY;")
     if uppercase(mode) in ["", "DEFERRED", "IMMEDIATE", "EXCLUSIVE"]
-        execute(db, "BEGIN $(mode) TRANSACTION;")
+        if already_in_transaction
+            # If already in a transaction, use a savepoint instead
+            execute(db, "SAVEPOINT $(mode);")
+        else
+            execute(db, "BEGIN $(mode) TRANSACTION;")
+        end
     else
         execute(db, "SAVEPOINT $(mode);")
     end
@@ -663,7 +678,9 @@ DBInterface.transaction(f, db::DB) = transaction(f, db)
 @inline function transaction(f::Function, db::DB)
     # generate a random name for the savepoint
     name = string("SQLITE", Random.randstring(10))
-    execute(db, "PRAGMA synchronous = OFF;")
+    already_in_transaction = intransaction(db)
+    # PRAGMA statements cannot be executed inside a transaction
+    already_in_transaction || execute(db, "PRAGMA synchronous = OFF;")
     transaction(db, name)
     try
         f()
@@ -673,7 +690,7 @@ DBInterface.transaction(f, db::DB) = transaction(f, db)
     finally
         # savepoints are not released on rollback
         commit(db, name)
-        execute(db, "PRAGMA synchronous = ON;")
+        already_in_transaction || execute(db, "PRAGMA synchronous = ON;")
     end
 end
 

test/runtests.jl

@@ -300,6 +300,44 @@ end
         end
     end
 
+    @testset "Issue #341: load! inside transaction" begin
+        db = SQLite.DB()
+        # Test that load! works when called inside an existing transaction
+        data = [(a=1, b="x"), (a=2, b="y"), (a=3, b="z")]
+
+        # First verify load! works outside a transaction
+        SQLite.load!(data, db, "test_outside")
+        result = DBInterface.execute(db, "SELECT * FROM test_outside") |> columntable
+        @test result.a == [1, 2, 3]
+        @test result.b == ["x", "y", "z"]
+
+        # Now test load! inside a transaction (this is what issue #341 reported as failing)
+        DBInterface.transaction(db) do
+            data2 = [(c=10, d="hello"), (c=20, d="world")]
+            SQLite.load!(data2, db, "test_inside")
+        end
+        result2 = DBInterface.execute(db, "SELECT * FROM test_inside") |> columntable
+        @test result2.c == [10, 20]
+        @test result2.d == ["hello", "world"]
+
+        # Test nested transaction with rollback
+        DBInterface.transaction(db) do
+            data3 = [(e=100,)]
+            SQLite.load!(data3, db, "test_rollback")
+            # This table should exist within the transaction
+            @test DBInterface.execute(db, "SELECT * FROM test_rollback") |> columntable |> x -> x.e == [100]
+        end
+        # Table should still exist after commit
+        @test DBInterface.execute(db, "SELECT * FROM test_rollback") |> columntable |> x -> x.e == [100]
+
+        # Test intransaction helper
+        @test SQLite.intransaction(db) == false
+        SQLite.transaction(db)
+        @test SQLite.intransaction(db) == true
+        SQLite.commit(db)
+        @test SQLite.intransaction(db) == false
+    end
+
     @testset "Dates" begin
         setup_clean_test_db() do db
             DBInterface.execute(db, "create table temp as select * from album")