feat: expands limit in select accepting null value (kysely-org#1347)

* feat: expands limit in select accepting null value

* explain in jsdocs, move test case.

Co-authored-by: Alessio Napolitano <121714208+alenap93@users.noreply.github.com>

---------

Co-authored-by: igalklebanov <igalklebanov@gmail.com>

src/query-builder/select-query-builder.ts

@@ -1124,6 +1124,9 @@ export interface SelectQueryBuilder<DB, TB extends keyof DB, O>
   /**
    * Adds a limit clause to the query.
    *
+   * Passing a `null` value is only supported by some dialects like PostgreSQL,
+   * and will result in a no-op limit clause.
+   *
    * ### Examples
    *
    * Select the first 10 rows of the result:
@@ -1160,7 +1163,7 @@ export interface SelectQueryBuilder<DB, TB extends keyof DB, O>
    * ```
    */
   limit(
-    limit: ValueExpression<DB, TB, number | bigint>,
+    limit: ValueExpression<DB, TB, number | bigint | null>,
   ): SelectQueryBuilder<DB, TB, O>
 
   /**
@@ -2417,7 +2420,7 @@ class SelectQueryBuilderImpl<DB, TB extends keyof DB, O>
   }
 
   limit(
-    limit: ValueExpression<DB, TB, number | bigint>,
+    limit: ValueExpression<DB, TB, number | bigint | null>,
   ): SelectQueryBuilder<DB, TB, O> {
     return new SelectQueryBuilderImpl({
       ...this.#props,

test/node/src/select.test.ts

@@ -1123,6 +1123,28 @@ for (const dialect of DIALECTS) {
       })
     }
 
+    if (dialect === 'postgres') {
+      it('should create a select query with limit null', async () => {
+        const query = ctx.db
+          .selectFrom('person')
+          .select('first_name')
+          .limit(null)
+
+        testSql(query, dialect, {
+          postgres: {
+            sql: `select "first_name" from "person" limit $1`,
+            parameters: [null],
+          },
+          mysql: NOT_SUPPORTED,
+          mssql: NOT_SUPPORTED,
+          sqlite: NOT_SUPPORTED,
+        })
+
+        const result = await query.execute()
+        expect(result).to.have.length(3)
+      })
+    }
+
     it('should create a select statement without a `from` clause', async () => {
       const query = ctx.db.selectNoFrom((eb) => [
         eb