Default tags to an empty slice, make not null

This adds a new migration v3 to adjust the tags column to ensure it's
never null, which helps simplify client implementations by not making
them deal with both null and empty array values.

Fixes #46.

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Database schema v3: alter river_job tags column to set a default of `[]` and add not null constraint.
+
 ## [0.0.7] - 2023-11-20
 
 ### Changed

client_test.go

@@ -658,7 +658,7 @@ func Test_Client_Insert(t *testing.T) {
 		require.Equal(t, (&noOpArgs{}).Kind(), jobRow.Kind)
 		require.Equal(t, PriorityDefault, jobRow.Priority)
 		require.Equal(t, QueueDefault, jobRow.Queue)
-		require.Equal(t, []string(nil), jobRow.Tags)
+		require.Equal(t, []string{}, jobRow.Tags)
 	})
 
 	t.Run("WithInsertOpts", func(t *testing.T) {
@@ -755,7 +755,7 @@ func Test_Client_InsertTx(t *testing.T) {
 		require.Equal(t, (&noOpArgs{}).Kind(), jobRow.Kind)
 		require.Equal(t, PriorityDefault, jobRow.Priority)
 		require.Equal(t, QueueDefault, jobRow.Queue)
-		require.Equal(t, []string(nil), jobRow.Tags)
+		require.Equal(t, []string{}, jobRow.Tags)
 
 		// Job is not visible outside of the transaction.
 		_, err = bundle.queries.JobGetByID(ctx, client.driver.GetDBPool(), jobRow.ID)
@@ -2790,7 +2790,7 @@ func TestInsert(t *testing.T) {
 				require.Equal(1, insertedJob.Priority)
 				// Default comes from database now(), and we can't know the exact value:
 				require.WithinDuration(time.Now(), insertedJob.ScheduledAt, 2*time.Second)
-				require.Equal([]string(nil), insertedJob.Tags)
+				require.Equal([]string{}, insertedJob.Tags)
 				// require.Equal([]byte("{}"), insertedJob.metadata)
 			},
 		},

internal/dbadapter/db_adapter.go

@@ -298,6 +298,10 @@ func (a *StandardAdapter) JobInsertManyTx(ctx context.Context, tx pgx.Tx, params
 			metadata = []byte("{}")
 		}
 
+		tags := params.Tags
+		if tags == nil {
+			tags = []string{}
+		}
 		insertJobsParams[i] = dbsqlc.JobInsertManyParams{
 			Args:        params.EncodedArgs,
 			Kind:        params.Kind,
@@ -306,7 +310,7 @@ func (a *StandardAdapter) JobInsertManyTx(ctx context.Context, tx pgx.Tx, params
 			Priority:    int16(min(params.Priority, math.MaxInt16)),
 			Queue:       params.Queue,
 			State:       params.State,
-			Tags:        params.Tags,
+			Tags:        tags,
 		}
 	}
 

internal/dbmigrate/002_initial_schema.up.sql

@@ -93,4 +93,4 @@ CREATE UNLOGGED TABLE river_leader(
 
   CONSTRAINT name_length CHECK (char_length(name) > 0 AND char_length(name) < 128),
   CONSTRAINT leader_id_length CHECK (char_length(leader_id) > 0 AND char_length(leader_id) < 128)
-);
+);

internal/dbmigrate/003_river_job_tags_non_null.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE river_job ALTER COLUMN tags DROP NOT NULL,
+                      ALTER COLUMN tags DROP DEFAULT;

internal/dbmigrate/003_river_job_tags_non_null.up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE river_job ALTER COLUMN tags SET NOT NULL,
+                      ALTER COLUMN tags SET DEFAULT '{}';

internal/dbsqlc/river_job.sql

@@ -24,7 +24,7 @@ CREATE TABLE river_job(
   queue text NOT NULL DEFAULT 'default' ::text,
   state river_job_state NOT NULL DEFAULT 'available' ::river_job_state,
   scheduled_at timestamptz NOT NULL DEFAULT NOW(),
-  tags varchar(255)[],
+  tags varchar(255)[] NOT NULL DEFAULT '{}' ::varchar(255)[],
   CONSTRAINT finalized_or_finalized_at_null CHECK ((state IN ('cancelled', 'completed', 'discarded') AND finalized_at IS NOT NULL) OR finalized_at IS NULL),
   CONSTRAINT priority_in_range CHECK (priority >= 1 AND priority <= 4),
   CONSTRAINT queue_length CHECK (char_length(queue) > 0 AND char_length(queue) < 128),
@@ -184,7 +184,7 @@ INSERT INTO river_job(
   @queue::text,
   coalesce(sqlc.narg('scheduled_at')::timestamptz, now()),
   @state::river_job_state,
-  @tags::varchar(255)[]
+  coalesce(@tags::varchar(255)[], '{}')
 ) RETURNING *;
 
 -- name: JobInsertMany :copyfrom