Emulate dropping a unique column on SQLite 3.35.0+

SQLite 3.35.0 added support for dropping columns, but not for
dropping unique columns, or columns that are part of an index
Fallback to the emulated support if the column being dropped is
part of an index (unique columns will have an index created for
them).

CHANGELOG

@@ -1,5 +1,7 @@
 === master
 
+* Emulate dropping a unique column or a column that is part of an index on SQLite 3.35.0+ (jeremyevans) (#2176)
+
 * Add :min_wait_timeout option to sharded_threaded connection pool and default to 0.1, fixes stalling observed on JRuby (jeremyevans)
 
 * Support MERGE RETURNING on PostgreSQL 17+ (jeremyevans)

lib/sequel/adapters/shared/sqlite.rb

@@ -245,7 +245,7 @@ def alter_table_sql(table, op)
             super
           end
         when :drop_column
-          if sqlite_version >= 33500
+          if sqlite_version >= 33500 && !indexes(table).any?{|_, h| h[:columns].include?(op[:name])}
             super
           else
             ocp = lambda{|oc| oc.delete_if{|c| c.to_s == op[:name].to_s}}

spec/adapters/sqlite_spec.rb

@@ -159,6 +159,41 @@
     @db[:fk].select_order_map([:a, :b, :c, :d, :e]).must_equal [[100, 10, 211, 212, 213]]
     @db.schema(:fk).map{|_,v| v[:generated]}.must_equal [false, false, true, true, true]
   end if DB.sqlite_version >= 33100
+
+  it "should support dropping a unique column" do
+    @db.create_table!(:fk){Integer :a; Integer :b, :unique=>true}
+    @db[:fk].insert(:a=>1, :b=>2)
+    @db.alter_table(:fk){drop_column :b}
+    @db[:fk].all.must_equal [{:a=>1}]
+  end
+
+  it "should support dropping a column with scalar index" do
+    @db.create_table!(:fk){Integer :a; Integer :b, index: true}
+    @db[:fk].insert(:a=>1, :b=>2)
+    @db.alter_table(:fk){drop_column :b}
+    @db[:fk].all.must_equal [{:a=>1}]
+  end
+
+  it "should support dropping a column that is part of a composite index" do
+    @db.create_table!(:fk){Integer :a; Integer :b; index [:a, :b]}
+    @db[:fk].insert(:a=>1, :b=>2)
+    @db.alter_table(:fk){drop_column :b}
+    @db[:fk].all.must_equal [{:a=>1}]
+  end
+
+  it "should support dropping a column that is not part of an index" do
+    @db.create_table!(:fk){Integer :a, index: true; Integer :b}
+    @db[:fk].insert(:a=>1, :b=>2)
+    @db.alter_table(:fk){drop_column :b}
+    @db[:fk].all.must_equal [{:a=>1}]
+  end
+
+  it "should support dropping a column for a table without an index" do
+    @db.create_table!(:fk){Integer :a; Integer :b}
+    @db[:fk].insert(:a=>1, :b=>2)
+    @db.alter_table(:fk){drop_column :b}
+    @db[:fk].all.must_equal [{:a=>1}]
+  end
 end
 
 describe "SQLite temporary views" do