Update drop column

Signed-off-by: Alexis Rico <[email protected]>

docs/config.json

@@ -97,7 +97,7 @@
         {
           "title": "Drop Column",
           "href": "/operations/drop_column",
-          "file": "docs/operations/drop_column.md"
+          "file": "docs/operations/drop_column.mdx"
         },
         {
           "title": "Drop Constraint (deprecated)",

docs/operations/README.md

@@ -8,31 +8,3 @@
   "operations": [...]
 }
 ```
-
-See the [examples](../../examples) directory for examples of each kind of operation.
-
-`pgroll` supports the following migration operations:
-
-- [Add column](./add_column.md)
-- [Alter column](./alter_column.md)
-  - [Rename column](./rename_column.md)
-  - [Change type](./change_type.md)
-  - [Change default](./change_default.md)
-  - [Change comment](./change_comment.md)
-  - [Add check constraint](./add_check_constraint.md)
-  - [Add foreign key](./add_foreign_key.md)
-  - [Add not null constraint](./add_not_null_constraint.md)
-  - [Drop not null constraint](./drop_not_null_constraint.md)
-  - [Add unique constraint](./add_unique_constraint.md)
-- [Create index](./create_index.md)
-- [Create table](./create_table.md)
-- [Create constraint](./create_constraint.md)
-- [Drop column](./drop_column.md)
-- [Drop constraint](./drop_constraint.md)
-- [Drop multi-column constraint](./drop_multi_column_constraint.md)
-- [Drop index](./drop_index.md)
-- [Drop table](./drop_table.md)
-- [Raw SQL](./raw_sql.md)
-- [Rename table](./rename_table.md)
-- [Rename constraint](./rename_constraint.md)
-- [Set replica identity](./set_replica_identity.md)

docs/operations/alter_column/README.md

@@ -3,13 +3,3 @@
 An alter column operation alters the properties of a column. The operation supports several sub-operations, described below.
 
 An alter column operation may contain multiple sub-operations. For example, a single alter column operation may rename a column, change its type, and add a check constraint.
-
-- [Rename column](./rename_column.md)
-- [Change type](./change_type.md)
-- [Change default](./change_default.md)
-- [Change comment](./change_comment.md)
-- [Add check constraint](./add_check_constraint.md)
-- [Add foreign key](./add_foreign_key.md)
-- [Add not null constraint](./add_not_null_constraint.md)
-- [Drop not null constraint](./drop_not_null_constraint.md)
-- [Add unique constraint](./add_unique_constraint.md)

docs/operations/drop_column.mdx

@@ -0,0 +1,25 @@
+# Drop column
+
+## Structure
+
+A drop column operation drops a column from an existing table.
+
+```json
+{
+  "drop_column": {
+    "table": "name of table",
+    "column": "name of column to drop",
+    "down": "SQL expression"
+  }
+}
+```
+
+The `down` field above is required in order to backfill the previous version of the schema during an active migration.
+
+## Examples
+
+### Drop a column with a default value
+
+If a new row is inserted against the new schema without a `price` column, the old schema `price` column will be set to `0`.
+
+<ExampleSnippet example="09_drop_column.json" />