issue_comments: 898063815

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html_url issue_url id node_id user created_at updated_at author_association body reactions issue performed_via_github_app
https://github.com/simonw/datasette/issues/1293#issuecomment-898063815 https://api.github.com/repos/simonw/datasette/issues/1293 898063815 IC_kwDOBm6k_c41h13H 9599 2021-08-13T00:33:17Z 2021-08-13T00:33:17Z OWNER

Improved version of that function: python def columns_for_query(conn, sql): """ Given a SQLite connection ``conn`` and a SQL query ``sql``, returns a list of ``(table_name, column_name)`` pairs, one per returned column. ``(None, None)`` if no table and column could be derived. """ rows = conn.execute('explain ' + sql).fetchall() table_rootpage_by_register = {r['p1']: r['p2'] for r in rows if r['opcode'] == 'OpenRead'} names_by_rootpage = dict( conn.execute( 'select rootpage, name from sqlite_master where rootpage in ({})'.format( ', '.join(map(str, table_rootpage_by_register.values())) ) ) ) columns_by_column_register = {} for row in rows: if row['opcode'] in ('Rowid', 'Column'): addr, opcode, table_id, cid, column_register, p4, p5, comment = row table = names_by_rootpage[table_rootpage_by_register[table_id]] columns_by_column_register[column_register] = (table, cid) result_row = [dict(r) for r in rows if r['opcode'] == 'ResultRow'][0] registers = list(range(result_row["p1"], result_row["p1"] + result_row["p2"])) all_column_names = {} for table in names_by_rootpage.values(): table_xinfo = conn.execute('pragma table_xinfo({})'.format(table)).fetchall() for row in table_xinfo: all_column_names[(table, row["cid"])] = row["name"] final_output = [] for r in registers: try: table, cid = columns_by_column_register[r] final_output.append((table, all_column_names[table, cid])) except KeyError: final_output.append((None, None)) return final_output It works!

```diff diff --git a/datasette/templates/query.html b/datasette/templates/query.html index 75f7f1b..9fe1d4f 100644 --- a/datasette/templates/query.html +++ b/datasette/templates/query.html @@ -67,6 +67,8 @@

</form>

+extra_column_info: {{ extra_column_info }} + {% if display_rows %}

This data as {% for name, url in renderers.items() %}{{ name }}{{ ", " if not loop.last }}{% endfor %}, CSV

<table class="rows-and-columns"> diff --git a/datasette/views/database.py b/datasette/views/database.py index 7c36034..02f8039 100644 --- a/datasette/views/database.py +++ b/datasette/views/database.py @@ -10,6 +10,7 @@ import markupsafe from datasette.utils import ( await_me_maybe, check_visibility, + columns_for_query, derive_named_parameters, to_css_class, validate_sql_select, @@ -248,6 +249,8 @@ class QueryView(DataView): query_error = None + extra_column_info = None + # Execute query - as write or as read if write: if request.method == "POST": @@ -334,6 +337,10 @@ class QueryView(DataView): database, sql, params_for_query, truncate=True, **extra_args ) columns = [r[0] for r in results.description] + + # Try to figure out extra column information + db = self.ds.get_database(database) + extra_column_info = await db.execute_fn(lambda conn: columns_for_query(conn, sql)) except sqlite3.DatabaseError as e: query_error = e results = None @@ -462,6 +469,7 @@ class QueryView(DataView): "show_hide_text": show_hide_text, "show_hide_hidden": markupsafe.Markup(show_hide_hidden), "hide_sql": hide_sql, + "extra_column_info": extra_column_info, } return ( ```
 
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