Supported operations

dtm renders typed diffs into Databricks (Unity Catalog) SQL via DatabricksStatementGenerator. Anything not listed below surfaces as UnsupportedDiffError in fail mode (default) or is dropped in skip mode.

All statements use three-level naming: catalog.schema.table.

Schema operations

#	Operation	Diff type	SQL emitted
1	Create schema	SchemaAdded	CREATE SCHEMA IF NOT EXISTS {catalog}.{schema};
2	Drop schema	SchemaRemoved	DROP SCHEMA IF EXISTS {catalog}.{schema} CASCADE;

SchemaChanged has no handled fields — any modification is unsupported.

Table operations

#	Operation	Diff type	SQL emitted
3	Create table	TableAdded	CREATE TABLE IF NOT EXISTS {catalog}.{schema}.{table} (<columns>[, PRIMARY KEY (<pk>)]);
4	Drop table	TableRemoved	DROP TABLE IF EXISTS {catalog}.{schema}.{table};

Create-table inlines column definitions (type, NOT NULL, DEFAULT, COMMENT) and a composite PRIMARY KEY clause when any column has is_key=true. TableChanged has no handled fields.

Column operations

#	Operation	Trigger (field delta)	SQL emitted
5	Add column	ColumnAdded	ALTER TABLE … ADD COLUMN <col_def>;
6	Drop column	ColumnRemoved	ALTER TABLE … DROP COLUMN IF EXISTS <name>;
7	Change type	data_type, data_type_length, data_type_precision, data_type_numeric_scale	ALTER TABLE … ALTER COLUMN <name> TYPE <new_type>;
8	Set NOT NULL	is_nullable: true → false	ALTER TABLE … ALTER COLUMN <name> SET NOT NULL;
9	Drop NOT NULL	is_nullable: false → true	ALTER TABLE … ALTER COLUMN <name> DROP NOT NULL;
10	Set / change comment	comment	ALTER TABLE … ALTER COLUMN <name> COMMENT '<new>';
11	Drop comment	comment: <any> → null	ALTER TABLE … ALTER COLUMN <name> COMMENT NULL;
12	Set / change default	constraints (non-null)	ALTER TABLE … ALTER COLUMN <name> SET DEFAULT <expr>;
13	Drop default	constraints: <any> → null	ALTER TABLE … ALTER COLUMN <name> DROP DEFAULT;
14	Add primary key	is_key: false/null → true	ALTER TABLE … ADD CONSTRAINT pk_<table> PRIMARY KEY (<name>);
15	Drop primary key	is_key: true → false/null	ALTER TABLE … DROP PRIMARY KEY;

A single ColumnChanged diff can emit several ALTER statements — one per field delta. Field deltas outside the allow-list above raise UnsupportedDiffError.

Type-change detection compares the rendered type string (int, decimal(18, 2), string), so crawler artifacts like precision=0, scale=0 on an INT column don't produce spurious ALTERs.

Catalog operations

Not supported. dtm never emits CREATE, ALTER, or DROP CATALOG. See scope for the rationale.

Renames

Not detected in v1. A rename surfaces as Removed + Added.

Known limitations

• Column drops require column-mapping mode. Databricks requires delta.columnMapping.mode = 'name' on the target table before any DROP COLUMN succeeds. Configure it once in project.yaml under platform_options.tables.properties — dtm then emits it on every CREATE TABLE. Note that this only covers newly created tables; for existing tables, set the property via a pre-deployment migration.
• Single-column PK only when toggled via is_key. Composite primary keys are only emitted on CREATE TABLE. Toggling is_key on an existing column generates a single-column PK constraint.