Fixing a few issues that became obvious when I was looking at examples of what gets sent to the API for table saving.

packages/builder/src/components/backend/DataTable/modals/CreateEditColumn.svelte

@@ -102,6 +102,9 @@
     if (field.type === AUTO_TYPE) {
       field = buildAutoColumn($tables.draft.name, field.name, field.subtype)
     }
+    if (field.type !== LINK_TYPE) {
+      delete field.fieldName
+    }
     try {
       await tables.saveField({
         originalName,

packages/builder/src/stores/backend/tables.js

@@ -122,7 +122,7 @@ export function createTablesStore() {
       update(state => {
         // delete the original if renaming
         // need to handle if the column had no name, empty string
-        if (originalName || originalName === "") {
+        if (originalName != null && originalName !== field.name) {
           delete state.draft.schema[originalName]
           state.draft._rename = {
             old: originalName,

packages/server/src/api/controllers/table/internal.js

@@ -44,14 +44,10 @@ exports.save = async function (ctx) {
   // the column if you want to change the type
   if (oldTable && oldTable.schema) {
     for (let propKey of Object.keys(tableToSave.schema)) {
-      let column = tableToSave.schema[propKey]
       let oldColumn = oldTable.schema[propKey]
       if (oldColumn && oldColumn.type === "internal") {
         oldColumn.type = "auto"
       }
-      if (oldColumn && oldColumn.type !== column.type) {
-        ctx.throw(400, "Cannot change the type of a column")
-      }
     }
   }