Merge pull request #83 from macbre/single_column

Report tables with just a single column

README.md

@@ -7,13 +7,13 @@ Analyses your database queries and schema and suggests indices improvements. You
 
 `index-digest` does the following:
 
-* it checks the schema of all tables in a given database and suggests improvements (e.g. removal of redundant indices, adding a primary key to ease replication)
+* it checks the schema of all tables in a given database and suggests improvements (e.g. removal of redundant indices, adding a primary key to ease replication, dropping tables with just a single column)
 * if provided with SQL queries log (via `--sql-log` option) it:
   * checks if all tables, columns and indices are used by these queries
   * reports text columns with character set different than `utf`
   * reports queries that do not use indices
   * reports queries that use filesort, temporary file or full table scan
-  * reports queries that are not quite kosher (e.g. `LIKE "%foo%"`)
+  * reports queries that are not quite kosher (e.g. `LIKE "%foo%"`, `INSERT IGNORE`)
 
 This tool **supports MySQL 5.5, 5.6, 5.7, 8.0 and MariaDB 10.0, 10.2** and runs under **Python 2.7, 3.4, 3.5 and 3.6**.
 
@@ -133,6 +133,16 @@ test_tables → table affected: 0075_some_guy_test_table
       PRIMARY KEY (`id`)
     ) ENGINE=InnoDB DEFAULT CHARSET=utf8
 
+------------------------------------------------------------
+single_column → table affected: 0074_bag_of_ints
+
+✗ "0074_bag_of_ints" has just a single column
+
+  - schema: CREATE TABLE `0074_bag_of_ints` (
+      `id` int(9) NOT NULL AUTO_INCREMENT,
+      PRIMARY KEY (`id`)
+    ) ENGINE=InnoDB DEFAULT CHARSET=utf8
+
 ------------------------------------------------------------
 not_used_indices → table affected: 0002_not_used_indices
 
@@ -252,6 +262,7 @@ Outputs YML file with results and metadata.
 * `non_utf_columns`: reports text columns that have characters encoding set to `latin1` (utf is the way to go)
 * `missing_primary_index`: reports tables with no primary or unique key (see [MySQL bug #76252](https://bugs.mysql.com/bug.php?id=76252) and [Wikia/app#9863](https://github.com/Wikia/app/pull/9863))
 * `test_tables`: reports tables that seem to be test leftovers (e.g. `some_guy_test_table`)
+* `single_column`: reports tables with just a single column
 
 ### Additional checks performed on SQL log
 

indexdigest/cli/script.py

@@ -45,7 +45,8 @@
     check_selects_with_like, \
     check_missing_primary_index, \
     check_test_tables, \
-    check_insert_ignore_queries
+    check_insert_ignore_queries, \
+    check_single_column
 
 
 def main():
@@ -80,6 +81,7 @@ def main():
         check_latin_columns(database),
         check_missing_primary_index(database),
         check_test_tables(database),
+        check_single_column(database),
     )
 
     # checks that use SQL log

indexdigest/linters/__init__.py

@@ -13,4 +13,5 @@
 from .linter_0032_utf_latin_columns import check_latin_columns
 from .linter_0034_missing_primary_index import check_missing_primary_index
 from .linter_0070_insert_ignore import check_insert_ignore_queries
+from .linter_0074_single_column import check_single_column
 from .linter_0075_test_tables import check_test_tables

indexdigest/linters/linter_0074_single_column.py

@@ -0,0 +1,22 @@
+"""
+This linter reports tables with just a single column
+"""
+from indexdigest.utils import LinterEntry
+
+
+def check_single_column(database):
+    """
+    :type database  indexdigest.database.Database
+    :rtype: list[LinterEntry]
+    """
+    tables = [
+        table
+        for table in database.get_tables()
+        if len(database.get_table_columns(table)) == 1
+    ]
+
+    for table in tables:
+        yield LinterEntry(linter_type='single_column', table_name=table,
+                          message='"{}" has just a single column'.
+                          format(table),
+                          context={'schema': database.get_table_schema(table)})

indexdigest/test/linters/test_0074_single_column.py

@@ -0,0 +1,22 @@
+from __future__ import print_function
+
+from unittest import TestCase
+
+from indexdigest.linters import check_single_column
+from indexdigest.test import DatabaseTestMixin
+
+
+class TestSingleColumn(TestCase, DatabaseTestMixin):
+
+    def test_check_single_column(self):
+        reports = list(check_single_column(self.connection))
+
+        print(list(map(str, reports)))
+
+        self.assertEqual(len(reports), 1)
+
+        self.assertEqual(str(reports[0]),
+                         '0074_bag_of_ints: "0074_bag_of_ints" has just a single column')
+        self.assertTrue('CREATE TABLE `0074_bag_of_ints` (' in reports[0].context['schema'])
+
+        # assert False

sql/0006-not-used-columns-and-tables.sql

@@ -18,7 +18,8 @@ INSERT INTO 0006_not_used_columns VALUES
 DROP TABLE IF EXISTS `0006_not_used_tables`;
 CREATE TABLE `0006_not_used_tables` (
 	`id` int(9) NOT NULL AUTO_INCREMENT,
+	`foo` varchar(16) NOT NULL DEFAULT '',
 	PRIMARY KEY (`id`)
 );
 
-INSERT INTO 0006_not_used_tables VALUES(1);
+INSERT INTO 0006_not_used_tables VALUES(1, 'foo');

sql/0074-single-column.sql

@@ -0,0 +1,8 @@
+-- Report tables with just a single column
+--
+-- https://github.com/macbre/index-digest/issues/74
+DROP TABLE IF EXISTS `0074_bag_of_ints`;
+CREATE TABLE `0074_bag_of_ints` (
+	`id` int(9) NOT NULL AUTO_INCREMENT,
+	PRIMARY KEY (`id`)
+) CHARSET=utf8;