fix: extract columns from sql statements within PG index definitions

src/__tests__/pg/_pg.test.ts

@@ -29,7 +29,7 @@ import {
 } from 'drizzle-orm/pg-core';
 import { compareContents } from '../utils';
 import { pgGenerate } from '~/generators';
-import { relations } from 'drizzle-orm';
+import { relations, sql } from 'drizzle-orm';
 
 const pathPrefix = './src/__tests__/pg/';
 
@@ -162,7 +162,8 @@ async function indexesTest() {
       index1: index('key_4').on(tbl.f3.desc()),
       index2: index('key_5').on(tbl.f3, tbl.f4),
       index3: index('key_6').on(tbl.f1.nullsFirst().desc()),
-      index4: index().on(tbl.f4)
+      index4: index().on(tbl.f4),
+      index5: index('key_7').using('btree', tbl.f1.asc(), sql`lower(${tbl.f2})`)
     })
   );
 

src/__tests__/pg/indexes.dbml

@@ -13,5 +13,6 @@ table table {
     (f3, f4) [name: 'key_5']
     f1 [name: 'key_6']
     f4
+    (f1, f2) [name: 'key_7']
   }
 }

src/generators/common.ts

@@ -9,7 +9,8 @@ import {
   getTableColumns,
   is,
   isTable,
-  Table
+  Table,
+  Column
 } from 'drizzle-orm';
 import {
   AnyInlineForeignKeys,
@@ -173,8 +174,12 @@ export abstract class BaseGenerator<
         dbml.tab(2);
 
         if (is(index, PgIndex) || is(index, MySqlIndex) || is(index, SQLiteIndex)) {
+          const configColumns = index.config.columns.flatMap((entry) =>
+            is(entry, SQL) ? entry.queryChunks.filter((v) => is(v, Column)) : entry
+          );
+
           const idxColumns = wrapColumns(
-            index.config.columns as AnyColumn[],
+            configColumns as AnyColumn[],
             this.buildQueryConfig.escapeName
           );
           const idxProperties = index.config.name