Support --limit in dsc ls, add backend support

- _select_simple now supports passing limit which results in a SQL LIMIT
  <N> clause.
- make sure OFFSET does not interfere with it (uses LIMIT as well)
- New -l option in dsc ls command.

discodos/cmd23/ls.py

@@ -16,6 +16,7 @@
 @click.argument("search_terms", metavar="SEARCH_TERMS", nargs=-1)
 @click.option("--order-by", "-o", type=str, help="order by DiscoBASE field")
 @click.option("--reverse", "-r", is_flag=True, help="reverse order")
+@click.option("--limit", "-l", type=int, help="limit results")
 @click.option(
     "--all", "--extra", "-a", "-e", "sales_extra", is_flag=True,
     help="""By default sales and collection items are displayed in a 'combined' view.
@@ -26,7 +27,7 @@
     """,
 )
 @click.pass_obj
-def ls_cmd(helper, search_terms, order_by, reverse, sales_extra):
+def ls_cmd(helper, search_terms, order_by, reverse, sales_extra, limit):
     """Searches and lists collection items.
 
     Supports key=value search. Available keys can be either full DiscoBASE field names
@@ -58,11 +59,13 @@ def update_user_interaction_helper(user):
             orderby=order_by,
             reverse_order=reverse,
             sales_extra=sales_extra,
+            limit=limit,
         )
     else:
         coll_ctrl.ls_releases(
             search_key_value,
             orderby=order_by,
             reverse_order=reverse,
             sales_extra=sales_extra,
+            limit=limit,
         )

discodos/ctrl/collection.py

@@ -1242,7 +1242,7 @@ def prepare_key_value_search(self, query):
         return kv
 
     def tui_ls_releases(
-        self, search_terms, orderby=None, reverse_order=False, sales_extra=False
+        self, search_terms, orderby=None, reverse_order=False, sales_extra=False, limit=None
     ):
         """search_terms is a key value dict: eg: d_artist: artistname"""
 
@@ -1259,6 +1259,7 @@ def tui_ls_releases(
                 reverse_order=reverse_order,
                 filter_cols=self.cli.cols_key_value_search.shortcuts_dict(),
                 sales_extra=sales_extra,
+                limit=limit,
             )
         except Exception as error:
             self.cli.p(error)
@@ -1281,7 +1282,7 @@ def tui_ls_releases(
         return
 
     def ls_releases(
-        self, search_terms, orderby=None, reverse_order=False, sales_extra=False
+        self, search_terms, orderby=None, reverse_order=False, sales_extra=False, limit=None
     ):
         """search_terms is a key value dict: eg: d_artist: artistname"""
 
@@ -1297,6 +1298,7 @@ def ls_releases(
                 reverse_order=reverse_order,
                 filter_cols=self.cli.cols_key_value_search.shortcuts_dict(),
                 sales_extra=sales_extra,
+                limit=limit,
             )
         except Exception as error:
             self.cli.p(error)

discodos/model/collection.py

@@ -797,7 +797,7 @@ def update_release_brainz(self, release_id, mbid, match_method):
 
     def key_value_search_releases(
         self, search_key_value=None, orderby=None, filter_cols=None,
-        custom_fields=None, reverse_order=False, sales_extra=False
+        custom_fields=None, reverse_order=False, sales_extra=False, limit=None,
     ):
         # filter_cols are defined in ViewCommon and passed via the controller call.
         replace_cols = filter_cols
@@ -882,6 +882,7 @@ def key_value_search_releases(
             join=join,
             union=union if sales_extra else None,
             reverse_order=reverse_order,
+            limit=limit,
         )
         return rows
 

discodos/model/database.py

@@ -102,6 +102,7 @@ def _select_simple(
         as_dict=False,
         union=None,
         reverse_order=False,
+        limit=None
     ):
         """Wrapper around the _select method. Puts together SELECT as string.
 
@@ -118,13 +119,15 @@ def _select_simple(
             as_dict (bool, optional): Return results as a dictionary.
             union (list, optional): List of dicts representing UNION statements.
                 Each dict has keys: fields_list, table, condition, join.
+            limit (int, optional): limit results.
 
         Returns:
             Query results from _select.
         """
         log.debug("DB: _select_simple: fetchone = %s", fetchone)
         fields_str = ", ".join(fields_list)
         join_clause = ""
+        limit_clause = ""
         if join:
             # Expecting join as a list of tuples: [(join_type, table, condition), ...]
             for join_type, join_table, join_cond in join:
@@ -133,7 +136,12 @@ def _select_simple(
         orderby_clause = f"ORDER BY {orderby}" if orderby else ""
         orderby_clause += " DESC" if reverse_order else ""
         select = "SELECT DISTINCT" if distinct else "SELECT"
-        limit = f"LIMIT -1 OFFSET {offset}" if offset else ""
+        if offset and limit:
+            limit_clause = f"LIMIT {limit} OFFSET {offset}"
+        elif offset:
+            limit_clause = f"LIMIT -1 OFFSET {offset}"
+        elif limit:
+            limit_clause = f"LIMIT {limit}"
 
         # Build the main SELECT query
         main_select = (
@@ -162,9 +170,9 @@ def _select_simple(
 
         select_str = (
             f"{main_select} UNION {' UNION '.join(union_queries)} "
-            f"{orderby_clause} {limit}"
+            f"{orderby_clause} {limit_clause}"
             if union_queries
-            else f"{main_select} {orderby_clause} {limit}"
+            else f"{main_select} {orderby_clause} {limit_clause}"
         )
         return self._select(select_str, fetchone, as_dict=as_dict)