Use pointers for schema and Table struct fields (#574)

Update the `schema` and `Tables` structs in the `schema` package to use
pointer types in fields.

As part of #239, the in-memory schema representation will need to be
updated more often and more accurately by individual operations in a
migration. Using pointers in these `schema` package structs makes this
possible.

Part of #239

pkg/migrations/duplicate_test.go

@@ -13,7 +13,7 @@ import (
 
 var table = &schema.Table{
 	Name: "test_table",
-	Columns: map[string]schema.Column{
+	Columns: map[string]*schema.Column{
 		"id":          {Name: "id", Type: "serial"},
 		"name":        {Name: "name", Type: "text"},
 		"nick":        {Name: "nick", Type: "text"},
@@ -22,21 +22,21 @@ var table = &schema.Table{
 		"city":        {Name: "city", Type: "text"},
 		"description": {Name: "description", Type: "text"},
 	},
-	UniqueConstraints: map[string]schema.UniqueConstraint{
+	UniqueConstraints: map[string]*schema.UniqueConstraint{
 		"unique_email":     {Name: "unique_email", Columns: []string{"email"}},
 		"unique_name_nick": {Name: "unique_name_nick", Columns: []string{"name", "nick"}},
 	},
-	CheckConstraints: map[string]schema.CheckConstraint{
+	CheckConstraints: map[string]*schema.CheckConstraint{
 		"email_at":        {Name: "email_at", Columns: []string{"email"}, Definition: `"email" ~ '@'`},
 		"adults":          {Name: "adults", Columns: []string{"age"}, Definition: `"age" > 18`},
 		"new_york_adults": {Name: "new_york_adults", Columns: []string{"city", "age"}, Definition: `"city" = 'New York' AND "age" > 21`},
 		"different_nick":  {Name: "different_nick", Columns: []string{"name", "nick"}, Definition: `"name" != "nick"`},
 	},
-	ForeignKeys: map[string]schema.ForeignKey{
+	ForeignKeys: map[string]*schema.ForeignKey{
 		"fk_city":      {Name: "fk_city", Columns: []string{"city"}, ReferencedTable: "cities", ReferencedColumns: []string{"id"}, OnDelete: "NO ACTION"},
 		"fk_name_nick": {Name: "fk_name_nick", Columns: []string{"name", "nick"}, ReferencedTable: "users", ReferencedColumns: []string{"name", "nick"}, OnDelete: "CASCADE"},
 	},
-	Indexes: map[string]schema.Index{
+	Indexes: map[string]*schema.Index{
 		"idx_no_kate": {
 			Name:       "idx_no_kate",
 			Columns:    []string{"name"},

pkg/migrations/op_add_column.go

@@ -59,7 +59,7 @@ func (o *OpAddColumn) Start(ctx context.Context, conn db.DB, latestSchema string
 		tableToBackfill = table
 	}
 
-	table.AddColumn(o.Column.Name, schema.Column{
+	table.AddColumn(o.Column.Name, &schema.Column{
 		Name: TemporaryName(o.Column.Name),
 	})
 
@@ -186,7 +186,7 @@ func (o *OpAddColumn) Validate(ctx context.Context, s *schema.Schema) error {
 
 	// Update the schema to ensure that the new column is visible to validation of
 	// subsequent operations.
-	table.AddColumn(o.Column.Name, schema.Column{
+	table.AddColumn(o.Column.Name, &schema.Column{
 		Name: TemporaryName(o.Column.Name),
 	})
 

pkg/migrations/op_alter_column.go

@@ -55,7 +55,7 @@ func (o *OpAlterColumn) Start(ctx context.Context, conn db.DB, latestSchema stri
 		// Add the new column to the internal schema representation. This is done
 		// here, before creation of the down trigger, so that the trigger can declare
 		// a variable for the new column.
-		table.AddColumn(o.Column, schema.Column{
+		table.AddColumn(o.Column, &schema.Column{
 			Name: TemporaryName(o.Column),
 		})
 

pkg/migrations/op_create_constraint.go

@@ -45,7 +45,7 @@ func (o *OpCreateConstraint) Start(ctx context.Context, conn db.DB, latestSchema
 			return nil, fmt.Errorf("failed to create up trigger: %w", err)
 		}
 
-		table.AddColumn(colName, schema.Column{
+		table.AddColumn(colName, &schema.Column{
 			Name: physicalColumnName,
 		})
 

pkg/migrations/op_create_table.go

@@ -112,13 +112,13 @@ func (o *OpCreateTable) Validate(ctx context.Context, s *schema.Schema) error {
 // updateSchema updates the in-memory schema representation with the details of
 // the new table.
 func (o *OpCreateTable) updateSchema(s *schema.Schema) *schema.Schema {
-	columns := make(map[string]schema.Column, len(o.Columns))
+	columns := make(map[string]*schema.Column, len(o.Columns))
 	for _, col := range o.Columns {
-		columns[col.Name] = schema.Column{
+		columns[col.Name] = &schema.Column{
 			Name: col.Name,
 		}
 	}
-	s.AddTable(o.Name, schema.Table{
+	s.AddTable(o.Name, &schema.Table{
 		Name:    o.Name,
 		Columns: columns,
 	})

pkg/migrations/op_drop_constraint.go

@@ -45,7 +45,7 @@ func (o *OpDropConstraint) Start(ctx context.Context, conn db.DB, latestSchema s
 	// Add the new column to the internal schema representation. This is done
 	// here, before creation of the down trigger, so that the trigger can declare
 	// a variable for the new column.
-	table.AddColumn(column.Name, schema.Column{
+	table.AddColumn(column.Name, &schema.Column{
 		Name: TemporaryName(column.Name),
 	})
 

pkg/migrations/op_drop_multicolumn_constraint.go

@@ -50,7 +50,7 @@ func (o *OpDropMultiColumnConstraint) Start(ctx context.Context, conn db.DB, lat
 		// Add the new column to the internal schema representation. This is done
 		// here, before creation of the down trigger, so that the trigger can declare
 		// a variable for the new column.
-		table.AddColumn(columnName, schema.Column{
+		table.AddColumn(columnName, &schema.Column{
 			Name: TemporaryName(columnName),
 		})
 

pkg/migrations/trigger.go

@@ -24,7 +24,7 @@ const (
 type triggerConfig struct {
 	Name           string
 	Direction      TriggerDirection
-	Columns        map[string]schema.Column
+	Columns        map[string]*schema.Column
 	SchemaName     string
 	TableName      string
 	PhysicalColumn string

pkg/migrations/trigger_test.go

@@ -20,7 +20,7 @@ func TestBuildFunction(t *testing.T) {
 			config: triggerConfig{
 				Name:      "triggerName",
 				Direction: TriggerDirectionUp,
-				Columns: map[string]schema.Column{
+				Columns: map[string]*schema.Column{
 					"id":       {Name: "id", Type: "int"},
 					"username": {Name: "username", Type: "text"},
 					"product":  {Name: "product", Type: "text"},
@@ -61,7 +61,7 @@ func TestBuildFunction(t *testing.T) {
 			config: triggerConfig{
 				Name:      "triggerName",
 				Direction: TriggerDirectionUp,
-				Columns: map[string]schema.Column{
+				Columns: map[string]*schema.Column{
 					"id":       {Name: "id", Type: "int"},
 					"username": {Name: "username", Type: "text"},
 					"product":  {Name: "product", Type: "text"},
@@ -106,7 +106,7 @@ func TestBuildFunction(t *testing.T) {
 			config: triggerConfig{
 				Name:      "triggerName",
 				Direction: TriggerDirectionDown,
-				Columns: map[string]schema.Column{
+				Columns: map[string]*schema.Column{
 					"id":       {Name: "id", Type: "int"},
 					"username": {Name: "username", Type: "text"},
 					"product":  {Name: "product", Type: "text"},
@@ -147,7 +147,7 @@ func TestBuildFunction(t *testing.T) {
 			config: triggerConfig{
 				Name:      "triggerName",
 				Direction: TriggerDirectionDown,
-				Columns: map[string]schema.Column{
+				Columns: map[string]*schema.Column{
 					"id":       {Name: "id", Type: "int"},
 					"username": {Name: "username", Type: "text"},
 					"product":  {Name: "product", Type: "text"},

pkg/roll/execute.go

@@ -260,7 +260,7 @@ func (m *Roll) Rollback(ctx context.Context) error {
 }
 
 // create view creates a view for the new version of the schema
-func (m *Roll) ensureView(ctx context.Context, version, name string, table schema.Table) error {
+func (m *Roll) ensureView(ctx context.Context, version, name string, table *schema.Table) error {
 	columns := make([]string, 0, len(table.Columns))
 	for k, v := range table.Columns {
 		columns = append(columns, fmt.Sprintf("%s AS %s", pq.QuoteIdentifier(v.Name), pq.QuoteIdentifier(k)))

pkg/schema/schema.go

@@ -18,7 +18,7 @@ import (
 
 func New() *Schema {
 	return &Schema{
-		Tables: make(map[string]Table),
+		Tables: make(map[string]*Table),
 	}
 }
 
@@ -27,7 +27,7 @@ type Schema struct {
 	// Name is the name of the schema
 	Name string `json:"name"`
 	// Tables is a map of virtual table name -> table mapping
-	Tables map[string]Table `json:"tables"`
+	Tables map[string]*Table `json:"tables"`
 }
 
 // Table represents a table in the schema
@@ -42,22 +42,22 @@ type Table struct {
 	Comment string `json:"comment"`
 
 	// Columns is a map of virtual column name -> column mapping
-	Columns map[string]Column `json:"columns"`
+	Columns map[string]*Column `json:"columns"`
 
 	// Indexes is a map of the indexes defined on the table
-	Indexes map[string]Index `json:"indexes"`
+	Indexes map[string]*Index `json:"indexes"`
 
 	// The columns that make up the primary key
 	PrimaryKey []string `json:"primaryKey"`
 
 	// ForeignKeys is a map of all foreign keys defined on the table
-	ForeignKeys map[string]ForeignKey `json:"foreignKeys"`
+	ForeignKeys map[string]*ForeignKey `json:"foreignKeys"`
 
 	// CheckConstraints is a map of all check constraints defined on the table
-	CheckConstraints map[string]CheckConstraint `json:"checkConstraints"`
+	CheckConstraints map[string]*CheckConstraint `json:"checkConstraints"`
 
 	// UniqueConstraints is a map of all unique constraints defined on the table
-	UniqueConstraints map[string]UniqueConstraint `json:"uniqueConstraints"`
+	UniqueConstraints map[string]*UniqueConstraint `json:"uniqueConstraints"`
 }
 
 // Column represents a column in a table
@@ -148,13 +148,13 @@ func (s *Schema) GetTable(name string) *Table {
 	if !ok {
 		return nil
 	}
-	return &t
+	return t
 }
 
 // AddTable adds a table to the schema
-func (s *Schema) AddTable(name string, t Table) {
+func (s *Schema) AddTable(name string, t *Table) {
 	if s.Tables == nil {
-		s.Tables = make(map[string]Table)
+		s.Tables = make(map[string]*Table)
 	}
 
 	s.Tables[name] = t
@@ -189,7 +189,7 @@ func (t *Table) GetColumn(name string) *Column {
 	if !ok {
 		return nil
 	}
-	return &c
+	return c
 }
 
 // ConstraintExists returns true if a constraint with the given name exists
@@ -234,9 +234,9 @@ func (t *Table) GetPrimaryKey() (columns []*Column) {
 }
 
 // AddColumn adds a column to the table
-func (t *Table) AddColumn(name string, c Column) {
+func (t *Table) AddColumn(name string, c *Column) {
 	if t.Columns == nil {
-		t.Columns = make(map[string]Column)
+		t.Columns = make(map[string]*Column)
 	}
 
 	t.Columns[name] = c