feat: Add PostgreSQL Extension Support

internal/diff/diff.go

@@ -42,6 +42,7 @@ const (
 	DiffTypePrivilege
 	DiffTypeRevokedDefaultPrivilege
 	DiffTypeColumnPrivilege
+	DiffTypeExtension
 )
 
 // String returns the string representation of DiffType
@@ -103,6 +104,8 @@ func (d DiffType) String() string {
 		return "revoked_default_privilege"
 	case DiffTypeColumnPrivilege:
 		return "column_privilege"
+	case DiffTypeExtension:
+		return "extension"
 	default:
 		return "unknown"
 	}
@@ -177,6 +180,8 @@ func (d *DiffType) UnmarshalJSON(data []byte) error {
 		*d = DiffTypeRevokedDefaultPrivilege
 	case "column_privilege":
 		*d = DiffTypeColumnPrivilege
+	case "extension":
+		*d = DiffTypeExtension
 	default:
 		return fmt.Errorf("unknown diff type: %s", s)
 	}
@@ -296,6 +301,9 @@ type ddlDiff struct {
 	addedColumnPrivileges    []*ir.ColumnPrivilege
 	droppedColumnPrivileges  []*ir.ColumnPrivilege
 	modifiedColumnPrivileges []*columnPrivilegeDiff
+	// Extensions
+	addedExtensions   []string
+	droppedExtensions []string
 }
 
 // schemaDiff represents changes to a schema
@@ -462,6 +470,26 @@ func GenerateMigration(oldIR, newIR *ir.IR, targetSchema string) []Diff {
 		modifiedColumnPrivileges:   []*columnPrivilegeDiff{},
 	}
 
+	// Compare extensions
+	oldExtSet := make(map[string]bool)
+	for _, ext := range oldIR.Extensions {
+		oldExtSet[ext] = true
+	}
+	for _, ext := range newIR.Extensions {
+		if !oldExtSet[ext] {
+			diff.addedExtensions = append(diff.addedExtensions, ext)
+		}
+	}
+	newExtSet := make(map[string]bool)
+	for _, ext := range newIR.Extensions {
+		newExtSet[ext] = true
+	}
+	for _, ext := range oldIR.Extensions {
+		if !newExtSet[ext] {
+			diff.droppedExtensions = append(diff.droppedExtensions, ext)
+		}
+	}
+
 	// Compare schemas first in deterministic order
 	schemaNames := sortedKeys(newIR.Schemas)
 	for _, name := range schemaNames {
@@ -1497,6 +1525,17 @@ func (d *ddlDiff) generatePreDropMaterializedViewsSQL(targetSchema string, colle
 
 // generateCreateSQL generates CREATE statements in dependency order
 func (d *ddlDiff) generateCreateSQL(targetSchema string, collector *diffCollector) {
+	for _, ext := range d.addedExtensions {
+		context := &diffContext{
+			Type:                DiffTypeExtension,
+			Operation:           DiffOperationCreate,
+			Path:                ext,
+			Source:              &ir.Extension{Name: ext},
+			CanRunInTransaction: true,
+		}
+		collector.collect(context, fmt.Sprintf("CREATE EXTENSION IF NOT EXISTS %s;", ir.QuoteIdentifier(ext)))
+	}
+
 	// Note: Schema creation is out of scope for schema-level comparisons
 
 	// Build function lookup early - needed for both domain and table dependency checks

internal/dump/formatter.go

@@ -116,7 +116,7 @@ func (f *DumpFormatter) FormatMultiFile(diffs []diff.Diff, outputPath string) er
 	}
 
 	// Create files in dependency order
-	orderedDirs := []string{"types", "domains", "sequences", "functions", "procedures", "tables", "views", "materialized_views", "default_privileges", "privileges"}
+	orderedDirs := []string{"extensions", "types", "domains", "sequences", "functions", "procedures", "tables", "views", "materialized_views", "default_privileges", "privileges"}
 
 	for _, dir := range orderedDirs {
 		if objects, exists := filesByType[dir]; exists {
@@ -235,6 +235,8 @@ func (f *DumpFormatter) writeObjectFile(filePath string, diffs []diff.Diff) erro
 // getObjectDirectory returns the directory name for an object type
 func (f *DumpFormatter) getObjectDirectory(objectType string) string {
 	switch objectType {
+	case "extension":
+		return "extensions"
 	case "type":
 		return "types"
 	case "domain":

internal/plan/plan.go

@@ -87,6 +87,7 @@ type TypeSummary struct {
 type Type string
 
 const (
+	TypeExtension               Type = "extensions"
 	TypeSchema                  Type = "schemas"
 	TypeType                    Type = "types"
 	TypeFunction                Type = "functions"
@@ -119,6 +120,7 @@ const (
 // getObjectOrder returns the dependency order for database objects
 func getObjectOrder() []Type {
 	return []Type{
+		TypeExtension,
 		TypeSchema,
 		TypeDefaultPrivilege,
 		TypeType,

ir/inspector.go

@@ -65,6 +65,10 @@ func (i *Inspector) BuildIR(ctx context.Context, targetSchema string) (*IR, erro
 		return nil, fmt.Errorf("failed to build schemas: %w", err)
 	}
 
+	if err := i.buildExtensions(ctx, schema, targetSchema); err != nil {
+		return nil, fmt.Errorf("failed to build extensions: %w", err)
+	}
+
 	if err := i.buildTables(ctx, schema, targetSchema); err != nil {
 		return nil, fmt.Errorf("failed to build tables: %w", err)
 	}
@@ -207,6 +211,64 @@ func (i *Inspector) buildMetadata(ctx context.Context, schema *IR) error {
 	return nil
 }
 
+func (i *Inspector) buildExtensions(ctx context.Context, schema *IR, targetSchema string) error {
+	query := `
+SELECT DISTINCT e.extname
+FROM pg_catalog.pg_depend d
+JOIN pg_catalog.pg_depend ed ON ed.objid = d.refobjid
+    AND ed.deptype = 'e'
+    AND ed.refclassid = 'pg_catalog.pg_extension'::regclass
+JOIN pg_catalog.pg_extension e ON e.oid = ed.refobjid
+WHERE d.deptype = 'n'
+  AND e.extname NOT IN ('plpgsql')
+  AND NOT EXISTS (
+    SELECT 1 FROM pg_catalog.pg_depend x
+    WHERE x.objid = d.objid AND x.deptype = 'e'
+  )
+  AND (
+    (d.classid = 'pg_catalog.pg_constraint'::regclass AND EXISTS (
+      SELECT 1 FROM pg_catalog.pg_constraint c
+      JOIN pg_catalog.pg_namespace n ON c.connamespace = n.oid
+      WHERE c.oid = d.objid AND n.nspname = $1
+    ))
+    OR
+    (d.classid = 'pg_catalog.pg_class'::regclass AND EXISTS (
+      SELECT 1 FROM pg_catalog.pg_class c
+      JOIN pg_catalog.pg_namespace n ON c.relnamespace = n.oid
+      WHERE c.oid = d.objid AND n.nspname = $1
+    ))
+    OR
+    (d.classid = 'pg_catalog.pg_type'::regclass AND EXISTS (
+      SELECT 1 FROM pg_catalog.pg_type t
+      JOIN pg_catalog.pg_namespace n ON t.typnamespace = n.oid
+      WHERE t.oid = d.objid AND n.nspname = $1
+    ))
+    OR
+    (d.classid = 'pg_catalog.pg_proc'::regclass AND EXISTS (
+      SELECT 1 FROM pg_catalog.pg_proc p
+      JOIN pg_catalog.pg_namespace n ON p.pronamespace = n.oid
+      WHERE p.oid = d.objid AND n.nspname = $1
+    ))
+  )
+ORDER BY e.extname`
+
+	rows, err := i.db.QueryContext(ctx, query, targetSchema)
+	if err != nil {
+		return fmt.Errorf("failed to query extensions: %w", err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var extname string
+		if err := rows.Scan(&extname); err != nil {
+			return fmt.Errorf("failed to scan extension: %w", err)
+		}
+		schema.Extensions = append(schema.Extensions, extname)
+	}
+
+	return rows.Err()
+}
+
 func (i *Inspector) buildSchemas(ctx context.Context, schema *IR, targetSchema string) error {
 	// Use the schema-specific query to prefilter at the database level
 	schemaName, err := i.queries.GetSchema(ctx, sql.NullString{String: targetSchema, Valid: true})

ir/inspector_extension_test.go

@@ -0,0 +1,39 @@
+package ir_test
+
+import (
+	"testing"
+
+	"github.com/pgplex/pgschema/testutil"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+)
+
+func TestExtensionDetection(t *testing.T) {
+	embeddedPG := testutil.SetupPostgres(t)
+	defer embeddedPG.Stop()
+
+	setupSQL := "CREATE EXTENSION IF NOT EXISTS btree_gist;"
+
+	t.Run("empty schema does not detect extensions", func(t *testing.T) {
+		ir := testutil.ParseSQLToIRWithSetup(t, embeddedPG, "-- empty", "public", setupSQL)
+		if len(ir.Extensions) != 0 {
+			t.Errorf("Expected no extensions for empty schema, got %v", ir.Extensions)
+		}
+	})
+
+	t.Run("schema with EXCLUDE constraint detects btree_gist", func(t *testing.T) {
+		sql := `
+CREATE TABLE reservations (
+    id uuid,
+    resource_id uuid NOT NULL,
+    start_date date NOT NULL,
+    end_date date NOT NULL,
+    CONSTRAINT reservations_pkey PRIMARY KEY (id),
+    CONSTRAINT no_overlap EXCLUDE USING gist (resource_id WITH =, daterange(start_date, end_date, '[]'::text) WITH &&)
+);`
+		ir := testutil.ParseSQLToIRWithSetup(t, embeddedPG, sql, "public", setupSQL)
+		if len(ir.Extensions) != 1 || ir.Extensions[0] != "btree_gist" {
+			t.Errorf("Expected [btree_gist], got %v", ir.Extensions)
+		}
+	})
+}

ir/ir.go

@@ -8,9 +8,10 @@ import (
 
 // IR represents the complete database schema intermediate representation
 type IR struct {
-	Metadata Metadata           `json:"metadata"`
-	Schemas  map[string]*Schema `json:"schemas"` // schema_name -> Schema
-	mu       sync.RWMutex       // Protects concurrent access to Schemas
+	Metadata   Metadata           `json:"metadata"`
+	Schemas    map[string]*Schema `json:"schemas"`              // schema_name -> Schema
+	Extensions []string           `json:"extensions,omitempty"` // Required extensions (e.g., btree_gist)
+	mu         sync.RWMutex       // Protects concurrent access to Schemas
 }
 
 // Metadata contains information about the schema dump
@@ -710,3 +711,10 @@ func (v *View) GetObjectName() string       { return v.Name }
 func (s *Sequence) GetObjectName() string   { return s.Name }
 func (t *Type) GetObjectName() string       { return t.Name }
 
+// Extension represents a required PostgreSQL extension
+type Extension struct {
+	Name string `json:"name"`
+}
+
+func (e *Extension) GetObjectName() string { return e.Name }
+

testdata/diff/create_table/add_column_cross_schema_custom_type/diff.sql

@@ -1,3 +1,5 @@
+CREATE EXTENSION IF NOT EXISTS citext;
+CREATE EXTENSION IF NOT EXISTS hstore;
 ALTER TABLE users ADD COLUMN fqdn citext NOT NULL;
 ALTER TABLE users ADD COLUMN metadata utils.hstore;
 ALTER TABLE users ADD COLUMN description utils.custom_text;

testdata/diff/create_table/add_column_cross_schema_custom_type/plan.json

@@ -8,6 +8,18 @@
   "groups": [
     {
       "steps": [
+        {
+          "sql": "CREATE EXTENSION IF NOT EXISTS citext;",
+          "type": "extension",
+          "operation": "create",
+          "path": "citext"
+        },
+        {
+          "sql": "CREATE EXTENSION IF NOT EXISTS hstore;",
+          "type": "extension",
+          "operation": "create",
+          "path": "hstore"
+        },
         {
           "sql": "ALTER TABLE users ADD COLUMN fqdn citext NOT NULL;",
           "type": "table.column",

testdata/diff/create_table/add_column_cross_schema_custom_type/plan.sql

@@ -1,3 +1,7 @@
+CREATE EXTENSION IF NOT EXISTS citext;
+
+CREATE EXTENSION IF NOT EXISTS hstore;
+
 ALTER TABLE users ADD COLUMN fqdn citext NOT NULL;
 
 ALTER TABLE users ADD COLUMN metadata utils.hstore;

testdata/diff/create_table/add_column_cross_schema_custom_type/plan.txt

@@ -1,8 +1,13 @@
-Plan: 1 to modify.
+Plan: 2 to add, 1 to modify.
 
 Summary by type:
+  extensions: 2 to add
   tables: 1 to modify
 
+Extensions:
+  + citext
+  + hstore
+
 Tables:
   ~ users
     + description (column)
@@ -13,6 +18,10 @@ Tables:
 DDL to be executed:
 --------------------------------------------------
 
+CREATE EXTENSION IF NOT EXISTS citext;
+
+CREATE EXTENSION IF NOT EXISTS hstore;
+
 ALTER TABLE users ADD COLUMN fqdn citext NOT NULL;
 
 ALTER TABLE users ADD COLUMN metadata utils.hstore;

testdata/diff/create_table/add_pk/diff.sql

@@ -1,3 +1,4 @@
+CREATE EXTENSION IF NOT EXISTS btree_gist;
 ALTER TABLE categories
 ADD COLUMN code text CONSTRAINT categories_pkey PRIMARY KEY;
 

testdata/diff/create_table/add_pk/plan.json

@@ -8,6 +8,12 @@
   "groups": [
     {
       "steps": [
+        {
+          "sql": "CREATE EXTENSION IF NOT EXISTS btree_gist;",
+          "type": "extension",
+          "operation": "create",
+          "path": "btree_gist"
+        },
         {
           "sql": "ALTER TABLE categories\nADD COLUMN code text CONSTRAINT categories_pkey PRIMARY KEY;",
           "type": "table.column",

testdata/diff/create_table/add_pk/plan.sql

@@ -1,3 +1,5 @@
+CREATE EXTENSION IF NOT EXISTS btree_gist;
+
 ALTER TABLE categories
 ADD COLUMN code text CONSTRAINT categories_pkey PRIMARY KEY;
 

testdata/diff/create_table/add_pk/plan.txt

@@ -1,8 +1,12 @@
-Plan: 7 to modify.
+Plan: 1 to add, 7 to modify.
 
 Summary by type:
+  extensions: 1 to add
   tables: 7 to modify
 
+Extensions:
+  + btree_gist
+
 Tables:
   ~ categories
     + code (column)
@@ -22,6 +26,8 @@ Tables:
 DDL to be executed:
 --------------------------------------------------
 
+CREATE EXTENSION IF NOT EXISTS btree_gist;
+
 ALTER TABLE categories
 ADD COLUMN code text CONSTRAINT categories_pkey PRIMARY KEY;
 

testdata/diff/dependency/extension_btree_gist/diff.sql

@@ -0,0 +1,10 @@
+CREATE EXTENSION IF NOT EXISTS btree_gist;
+CREATE TABLE IF NOT EXISTS reservations (
+    id uuid,
+    resource_id uuid NOT NULL,
+    start_date date NOT NULL,
+    end_date date NOT NULL,
+    CONSTRAINT reservations_pkey PRIMARY KEY (id),
+    CONSTRAINT valid_period CHECK (end_date >= start_date),
+    CONSTRAINT no_overlap EXCLUDE USING gist (resource_id WITH =, daterange(start_date, end_date, '[]'::text) WITH &&)
+);

testdata/diff/dependency/extension_btree_gist/new.sql

@@ -0,0 +1,9 @@
+CREATE TABLE public.reservations (
+    id uuid,
+    resource_id uuid NOT NULL,
+    start_date date NOT NULL,
+    end_date date NOT NULL,
+    CONSTRAINT reservations_pkey PRIMARY KEY (id),
+    CONSTRAINT valid_period CHECK (end_date >= start_date),
+    CONSTRAINT no_overlap EXCLUDE USING gist (resource_id WITH =, daterange(start_date, end_date, '[]'::text) WITH &&)
+);

testdata/diff/dependency/extension_btree_gist/old.sql

@@ -0,0 +1 @@
+-- Empty schema