feat: add support for Postgres 10+ GENERATED ALWAYS AS IDENTITY

allow developers to create a PrimaryGeneratedColumn of identity
and choose between `ALWAYS` and `BY DEFAULT`.

Closes: typeorm#8370

docs/decorator-reference.md

@@ -240,7 +240,7 @@ export class User {
 There are four generation strategies:
 
 * `increment` - uses AUTO_INCREMENT / SERIAL / SEQUENCE (depend on database type) to generate incremental number.
-* `identity` - only for [PostgreSQL 10+](https://www.postgresql.org/docs/13/sql-createtable.html). Postgres versions above 10 support the SQL-Compliant **IDENTITY** column. When marking the generation strategy as `identity` the column will be produced using `GENERATED BY DEFAULT AS IDENTITY`
+* `identity` - only for [PostgreSQL 10+](https://www.postgresql.org/docs/13/sql-createtable.html). Postgres versions above 10 support the SQL-Compliant **IDENTITY** column. When marking the generation strategy as `identity` together with the `generatedIdentity` option the column will be produced using `GENERATED [ALWAYS|BY DEFAULT] AS IDENTITY`
 * `uuid` - generates unique `uuid` string.
 * `rowid` - only for [CockroachDB](https://www.cockroachlabs.com/docs/stable/serial.html). Value is automatically generated using the `unique_rowid()`
 function. This produces a 64-bit integer from the current timestamp and ID of the node executing the `INSERT` or `UPSERT` operation.

src/decorator/columns/PrimaryGeneratedColumn.ts

@@ -3,6 +3,7 @@ import {PrimaryGeneratedColumnNumericOptions} from "../options/PrimaryGeneratedC
 import {PrimaryGeneratedColumnUUIDOptions} from "../options/PrimaryGeneratedColumnUUIDOptions";
 import {GeneratedMetadataArgs} from "../../metadata-args/GeneratedMetadataArgs";
 import { ColumnOptions } from "../options/ColumnOptions";
+import { PrimaryGeneratedColumnIdentityOptions } from "../options/PrimaryGeneratedColumnIdentityOptions";
 
 /**
  * Column decorator is used to mark a specific class property as a table column.
@@ -29,15 +30,15 @@ export function PrimaryGeneratedColumn(strategy: "uuid", options?: PrimaryGenera
  */
 export function PrimaryGeneratedColumn(strategy: "rowid", options?: PrimaryGeneratedColumnUUIDOptions): PropertyDecorator;
 
-export function PrimaryGeneratedColumn(strategy: "identity", options?: PrimaryGeneratedColumnUUIDOptions): PropertyDecorator;
+export function PrimaryGeneratedColumn(strategy: "identity", options?: PrimaryGeneratedColumnIdentityOptions): PropertyDecorator;
 
 /**
  * Column decorator is used to mark a specific class property as a table column.
  * Only properties decorated with this decorator will be persisted to the database when entity be saved.
  * This column creates an integer PRIMARY COLUMN with generated set to true.
  */
 export function PrimaryGeneratedColumn(strategyOrOptions?: "increment"|"uuid"|"rowid"|"identity"|PrimaryGeneratedColumnNumericOptions|PrimaryGeneratedColumnUUIDOptions,
-                                       maybeOptions?: PrimaryGeneratedColumnNumericOptions|PrimaryGeneratedColumnUUIDOptions): PropertyDecorator {
+                                       maybeOptions?: PrimaryGeneratedColumnNumericOptions|PrimaryGeneratedColumnUUIDOptions|PrimaryGeneratedColumnIdentityOptions): PropertyDecorator {
 
     // normalize parameters
     const options: ColumnOptions = {};

src/decorator/options/ColumnOptions.ts

@@ -143,6 +143,11 @@ export interface ColumnOptions extends ColumnCommonOptions {
      */
     generatedType?: "VIRTUAL"|"STORED";
 
+    /**
+     * Identity column type. Supported only in Postgres 10+.
+     */
+    generatedIdentity?: "ALWAYS"|"BY DEFAULT";
+
     /**
      * Return type of HSTORE column.
      * Returns value as string or as object.

src/decorator/options/PrimaryGeneratedColumnIdentityOptions.ts

@@ -0,0 +1,27 @@
+import {PrimaryGeneratedColumnType} from "../../driver/types/ColumnTypes";
+
+/**
+ * Describes all options for PrimaryGeneratedColumn decorator with identity generation strategy.
+ */
+export interface PrimaryGeneratedColumnIdentityOptions {
+
+    /**
+     * Column type. Must be one of the value from the ColumnTypes class.
+     */
+    type?: PrimaryGeneratedColumnType;
+
+    /**
+     * Column name in the database.
+     */
+    name?: string;
+
+    /**
+     * Column comment. Not supported by all database types.
+     */
+    comment?: string;
+
+    /**
+     * Identity column type. Supports only in Postgres 10+.
+     */
+     generatedIdentity?: "ALWAYS"|"BY DEFAULT";
+}

src/driver/postgres/PostgresQueryRunner.ts

@@ -1785,6 +1785,7 @@ export class PostgresQueryRunner extends BaseQueryRunner implements QueryRunner
                     if (dbColumn.is_identity === "YES") { // Postgres 10+ Identity column
                         tableColumn.isGenerated = true;
                         tableColumn.generationStrategy = "identity";
+                        tableColumn.generatedIdentity = dbColumn.identity_generation;
                     } else if (dbColumn["column_default"] !== null && dbColumn["column_default"] !== undefined) {
                         const serialDefaultName = `nextval('${this.buildSequenceName(table, dbColumn["column_name"])}'::regclass)`;
                         const serialDefaultPath = `nextval('${this.buildSequencePath(table, dbColumn["column_name"])}'::regclass)`;
@@ -2334,7 +2335,8 @@ export class PostgresQueryRunner extends BaseQueryRunner implements QueryRunner
         let c = "\"" + column.name + "\"";
         if (column.isGenerated === true && column.generationStrategy !== "uuid") {
             if (column.generationStrategy === "identity") { // Postgres 10+ Identity generated column
-                c += ` ${column.type} GENERATED BY DEFAULT AS IDENTITY`;
+                const generatedIdentityOrDefault = column.generatedIdentity || "BY DEFAULT";
+                c += ` ${column.type} GENERATED ${generatedIdentityOrDefault} AS IDENTITY`;
             } else { // classic SERIAL primary column
                 if (column.type === "integer" || column.type === "int" || column.type === "int4")
                     c += " SERIAL";

src/schema-builder/table/TableColumn.ts

@@ -45,6 +45,11 @@ export class TableColumn {
      */
     generationStrategy?: "uuid"|"increment"|"rowid"|"identity";
 
+       /**
+     * Identity column type. Supported only in Postgres 10+.
+     */
+    generatedIdentity?: "ALWAYS"|"BY DEFAULT";
+
     /**
      * Indicates if column is a primary key.
      */

test/github-issues/8370/entity/User.ts

@@ -0,0 +1,30 @@
+import { Column, Entity, PrimaryGeneratedColumn } from "../../../../src";
+
+@Entity()
+export class User {
+    // yest primary generated column
+    @PrimaryGeneratedColumn("identity", {
+        generatedIdentity: "ALWAYS",
+    })
+    id: number;
+
+    // test generatedIdentity=ALWAYS
+    @Column({
+        type: "bigint",
+        generated: "identity",
+        generatedIdentity: "ALWAYS",
+    })
+    secondId: number;
+
+    // test generatedIdentity=BY DEFAULT
+    @Column({
+        type: "int",
+        generated: "identity",
+        generatedIdentity: "BY DEFAULT",
+    })
+    thirdId: number;
+
+    // test default behavior of `generatedIdentity`
+    @Column({ type: "int", generated: "identity" })
+    fourthId: number;
+}

test/github-issues/8370/issue-8370.ts

@@ -0,0 +1,59 @@
+import "reflect-metadata";
+import {
+    createTestingConnections,
+    closeTestingConnections,
+} from "../../utils/test-utils";
+import { Connection } from "../../../src";
+import { User } from "./entity/User";
+
+import { expect } from "chai";
+
+describe("github issues > #8370 Add support for Postgres GENERATED ALWAYS AS IDENTITY", () => {
+    let connections: Connection[];
+    before(
+        async () =>
+            (connections = await createTestingConnections({
+                entities: [User],
+                schemaCreate: false,
+                dropSchema: true,
+                enabledDrivers: ["postgres"],
+            }))
+    );
+    after(() => closeTestingConnections(connections));
+
+    it("should produce proper SQL for creating a table identity columns", () =>
+        Promise.all(
+            connections.map(async (connection) => {
+                const sqlInMemory = await connection.driver
+                    .createSchemaBuilder()
+                    .log();
+                expect(sqlInMemory)
+                    .to.have.property("upQueries")
+                    .that.is.an("array")
+                    .and.has.length(1);
+                expect(sqlInMemory.upQueries[0])
+                    .to.have.property("query")
+                    .that.contain(
+                        `"id" integer GENERATED BY DEFAULT AS IDENTITY NOT NULL`
+                    );
+
+                expect(sqlInMemory.upQueries[0])
+                    .to.have.property("query")
+                    .that.contain(
+                        `"secondId" bigint GENERATED ALWAYS AS IDENTITY NOT NULL`
+                    );
+
+                expect(sqlInMemory.upQueries[0])
+                    .to.have.property("query")
+                    .that.contain(
+                        `"thirdId" integer GENERATED BY DEFAULT AS IDENTITY NOT NULL`
+                    );
+
+                expect(sqlInMemory.upQueries[0])
+                    .to.have.property("query")
+                    .that.contain(
+                        `"fourthId" integer GENERATED BY DEFAULT AS IDENTITY NOT NULL`
+                    );
+            })
+        ));
+});