Fix unique key missing problem with search (#232)

When creating embeddings, we store the unique key attnum in pg_options. 
Previously, the unique key attnum was taken from the original table, so
the error occurs if the
embedding table and the original table have a different number or order
of columns.
This patch saves the unique key attnum from the embedding table instead.

greenplumpython/experimental/embedding.py

@@ -155,6 +155,9 @@ def create_index(
         query_col_names = _serialize_to_expr(
             list(self._dataframe.unique_key) + [column], self._dataframe._db
         )
+        unique_key_col_names = _serialize_to_expr(
+            list(self._dataframe.unique_key), self._dataframe._db
+        )
         sql_add_relationship = f"""
             DO $$
             BEGIN
@@ -168,13 +171,21 @@ def create_index(
                             SELECT FROM unnest({query_col_names}) AS query
                             WHERE attname = query
                         )
+                ),emb_attnum_map AS (
+                    SELECT attname, attnum FROM pg_attribute
+                    WHERE 
+                        attrelid = '{embedding_df._qualified_table_name}'::regclass::oid AND
+                        EXISTS (
+                            SELECT FROM unnest({unique_key_col_names}) AS query
+                            WHERE attname = query
+                        )
                 ), embedding_info AS (
                     SELECT 
                         '{embedding_df._qualified_table_name}'::regclass::oid AS embedding_relid,
                         attnum AS content_attnum,
                         {len(self._dataframe._unique_key) + 1} AS embedding_attnum,
                         '{model_name}' AS model,
-                        ARRAY(SELECT attnum FROM attnum_map WHERE attname != '{column}') AS unique_key
+                        ARRAY(SELECT attnum FROM emb_attnum_map WHERE attname != '{column}') AS unique_key
                     FROM attnum_map
                     WHERE attname = '{column}'
                 )