diff --git a/Sources/PostgREST/PostgrestQueryBuilder.swift b/Sources/PostgREST/PostgrestQueryBuilder.swift
index 4e1507a7..1a20263b 100644
--- a/Sources/PostgREST/PostgrestQueryBuilder.swift
+++ b/Sources/PostgREST/PostgrestQueryBuilder.swift
@@ -69,15 +69,11 @@ public final class PostgrestQueryBuilder: PostgrestBuilder {
       if !prefersHeaders.isEmpty {
         $0.request.headers["Prefer"] = prefersHeaders.joined(separator: ",")
       }
-
-      // TODO: How to do this in Swift?
-      // if (Array.isArray(values)) {
-      //     const columns = values.reduce((acc, x) => acc.concat(Object.keys(x)), [] as string[])
-      //     if (columns.length > 0) {
-      //         const uniqueColumns = [...new Set(columns)].map((column) => `"${column}"`)
-      //         this.url.searchParams.set('columns', uniqueColumns.join(','))
-      //     }
-      // }
+      if let body = $0.request.body, let jsonObject = try JSONSerialization.jsonObject(with: body) as? [[String: Any]] {
+        let allKeys = jsonObject.flatMap(\.keys)
+        let uniqueKeys = Set(allKeys).sorted()
+        $0.request.query.append(URLQueryItem(name: "columns", value: uniqueKeys.joined(separator: ",")))
+      }
     }
 
     return PostgrestFilterBuilder(self)
@@ -118,6 +114,12 @@ public final class PostgrestQueryBuilder: PostgrestBuilder {
       if !prefersHeaders.isEmpty {
         $0.request.headers["Prefer"] = prefersHeaders.joined(separator: ",")
       }
+
+      if let body = $0.request.body, let jsonObject = try JSONSerialization.jsonObject(with: body) as? [[String: Any]] {
+        let allKeys = jsonObject.flatMap(\.keys)
+        let uniqueKeys = Set(allKeys).sorted()
+        $0.request.query.append(URLQueryItem(name: "columns", value: uniqueKeys.joined(separator: ",")))
+      }
     }
     return PostgrestFilterBuilder(self)
   }
diff --git a/Tests/PostgRESTTests/BuildURLRequestTests.swift b/Tests/PostgRESTTests/BuildURLRequestTests.swift
index 2ef87882..4753ba04 100644
--- a/Tests/PostgRESTTests/BuildURLRequestTests.swift
+++ b/Tests/PostgRESTTests/BuildURLRequestTests.swift
@@ -10,19 +10,43 @@ import XCTest
   import FoundationNetworking
 #endif
 
+struct User: Encodable {
+  var email: String
+  var username: String?
+}
+
 @MainActor
 final class BuildURLRequestTests: XCTestCase {
   let url = URL(string: "https://example.supabase.co")!
 
   struct TestCase: Sendable {
     let name: String
-    var record = false
+    let record: Bool
+    let file: StaticString
+    let line: UInt
     let build: @Sendable (PostgrestClient) async throws -> PostgrestBuilder
+
+    init(
+      name: String,
+      record: Bool = false,
+      file: StaticString = #file,
+      line: UInt = #line,
+      build: @escaping @Sendable (PostgrestClient) async throws -> PostgrestBuilder
+    ) {
+      self.name = name
+      self.record = record
+      self.file = file
+      self.line = line
+      self.build = build
+    }
   }
 
   func testBuildRequest() async throws {
     let runningTestCase = ActorIsolated(TestCase?.none)
 
+    let encoder = PostgrestClient.Configuration.jsonEncoder
+    encoder.outputFormatting = .sortedKeys
+
     let client = PostgrestClient(
       url: url,
       schema: nil,
@@ -39,12 +63,15 @@ final class BuildURLRequestTests: XCTestCase {
             as: .curl,
             named: runningTestCase.name,
             record: runningTestCase.record,
-            testName: "testBuildRequest()"
+            file: runningTestCase.file, 
+            testName: "testBuildRequest()",
+            line: runningTestCase.line
           )
         }
 
         return (Data(), URLResponse())
-      }
+      },
+      encoder: encoder
     )
 
     let testCases: [TestCase] = [
@@ -55,7 +82,16 @@ final class BuildURLRequestTests: XCTestCase {
       },
       TestCase(name: "insert new user") { client in
         try await client.from("users")
-          .insert(["email": "johndoe@supabase.io"])
+          .insert(User(email: "johndoe@supabase.io"))
+      },
+      TestCase(name: "bulk insert users") { client in
+        try await client.from("users")
+          .insert(
+            [
+              User(email: "johndoe@supabase.io"),
+              User(email: "johndoe2@supabase.io", username: "johndoe2"),
+            ]
+          )
       },
       TestCase(name: "call rpc") { client in
         try await client.rpc("test_fcn", params: ["KEY": "VALUE"])
@@ -89,11 +125,20 @@ final class BuildURLRequestTests: XCTestCase {
       },
       TestCase(name: "test upsert not ignoring duplicates") { client in
         try await client.from("users")
-          .upsert(["email": "johndoe@supabase.io"])
+          .upsert(User(email: "johndoe@supabase.io"))
+      },
+      TestCase(name: "bulk upsert") { client in
+        try await client.from("users")
+          .upsert(
+            [
+              User(email: "johndoe@supabase.io"),
+              User(email: "johndoe2@supabase.io", username: "johndoe2"),
+            ]
+          )
       },
       TestCase(name: "test upsert ignoring duplicates") { client in
         try await client.from("users")
-          .upsert(["email": "johndoe@supabase.io"], ignoreDuplicates: true)
+          .upsert(User(email: "johndoe@supabase.io"), ignoreDuplicates: true)
       },
       TestCase(name: "query with + character") { client in
         await client.from("users")
@@ -110,7 +155,7 @@ final class BuildURLRequestTests: XCTestCase {
         await client.schema("storage")
           .from("objects")
           .select()
-      }
+      },
     ]
 
     for testCase in testCases {
diff --git a/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-insert-users.txt b/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-insert-users.txt
new file mode 100644
index 00000000..e9fdf5b6
--- /dev/null
+++ b/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-insert-users.txt
@@ -0,0 +1,7 @@
+curl \
+	--request POST \
+	--header "Accept: application/json" \
+	--header "Content-Type: application/json" \
+	--header "X-Client-Info: postgrest-swift/x.y.z" \
+	--data "[{\"email\":\"johndoe@supabase.io\"},{\"email\":\"johndoe2@supabase.io\",\"username\":\"johndoe2\"}]" \
+	"https://example.supabase.co/users?columns=email,username"
\ No newline at end of file
diff --git a/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-upsert.txt b/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-upsert.txt
new file mode 100644
index 00000000..43a239d3
--- /dev/null
+++ b/Tests/PostgRESTTests/__Snapshots__/BuildURLRequestTests/testBuildRequest.bulk-upsert.txt
@@ -0,0 +1,8 @@
+curl \
+	--request POST \
+	--header "Accept: application/json" \
+	--header "Content-Type: application/json" \
+	--header "Prefer: resolution=merge-duplicates,return=representation" \
+	--header "X-Client-Info: postgrest-swift/x.y.z" \
+	--data "[{\"email\":\"johndoe@supabase.io\"},{\"email\":\"johndoe2@supabase.io\",\"username\":\"johndoe2\"}]" \
+	"https://example.supabase.co/users?columns=email,username"
\ No newline at end of file