feat: add column.isGenerated

Add generated columns support for PostgreSQL 12 and later

fix #88

Author: ozum

module-files/sql/12/column.sql

@@ -0,0 +1,36 @@
+SELECT
+  a.attrelid AS "parentOid",
+  a.atttypid AS "typeOid",
+  a.attnum AS "attributeNumber",
+  c.relkind AS "parentKind", -- r: table, i: index, S: sequence, t: TOAST table, v: view, m: materialized view, c: composite type, f: foreign table, p: partitioned table, I: partitioned index
+  a.attname AS "name",
+  pg_get_expr(ad.adbin, ad.adrelid)::information_schema.character_data AS "defaultWithTypeCast",
+  a.attnotnull AS "notNull",
+  format_type(a.atttypid, atttypmod) AS "sqlType",
+  CASE
+    WHEN c.relkind = 'v' AND a.attndims = 0 AND right(format_type(a.atttypid, atttypmod), 2) = '[]' THEN 1 -- Cannot find a way to detect array dimensions in views.
+    ELSE a.attndims
+  END AS "arrayDimension",
+  a.attnum AS position,
+  d.description AS "comment",
+  a.attgenerated <> '' AS "isGenerated"
+FROM
+  pg_attribute a
+  INNER JOIN pg_class c ON a.attrelid = c.oid
+  LEFT JOIN pg_attrdef ad ON (a.attrelid = ad.adrelid
+      AND a.attnum = ad.adnum)
+  LEFT JOIN pg_description d ON (a.attrelid = d.objoid
+      AND a.attnum = d.objsubid)
+WHERE
+  c.relnamespace = ANY ($1)
+  AND a.attnum > 0
+  AND NOT a.attisdropped
+  AND c.relkind IN ('m',
+    'r',
+    'v',
+    'c',
+    'p')
+ORDER BY
+  c.relnamespace,
+  LOWER(c.relname),
+  a.attnum

src/pg-structure/column.ts

@@ -26,6 +26,7 @@ export interface ColumnConstructorArgs extends DbObjectConstructorArgs {
   arrayDimension: number;
   defaultWithTypeCast: string | null;
   attributeNumber: number;
+  isGenerated?: boolean;
 }
 
 /**
@@ -49,6 +50,7 @@ export default class Column extends DbObject {
     this.attributeNumber = args.attributeNumber;
     this.minValue = this.isSerial ? 1 : NUMERIC_BOUNDRIES?.[this.type.name]?.min;
     this.maxValue = NUMERIC_BOUNDRIES?.[this.type.name]?.max;
+    this.isGenerated = args.isGenerated === true;
   }
 
   /**
@@ -123,6 +125,9 @@ export default class Column extends DbObject {
     return isSerial(this.defaultWithTypeCast);
   }
 
+  /** Whether this column is a generated column. */
+  public readonly isGenerated: boolean;
+
   /**
    * - If data type identifies an exact numeric type, this contains the (declared or implicit) scale
    *   of the type for this attribute. The scale indicates the number of significant digits to the right of the decimal point.

src/types/query-result.ts

@@ -64,6 +64,7 @@ export interface ColumnQueryResult {
   arrayDimension: number;
   position: number;
   comment: string | null;
+  isGenerated?: boolean;
 }
 
 /** @ignore */

test/column.test.ts

@@ -169,4 +169,8 @@ describe("Column", () => {
   it("should have uniqueIndexesNoPk.", () => {
     expect(idColumn.uniqueIndexesNoPk.map((i) => i.name)).toEqual(["ix_partial_unique"]);
   });
+
+  it("should return false for non generated columns", () => {
+    expect(accountTable.get("name").isGenerated).toBeFalsy();
+  });
 });

test/pg-structure.test.ts

@@ -86,6 +86,6 @@ describe("pgStructure()", () => {
   it("should accept options as first argument and reads client config from environment variables.", async () => {
     process.env.DBPX_USER = "xyz-user";
     process.env.DBPX_PASSWORD = "wrong-password";
-    await expect(pgStructure({ envPrefix: "DBPX", name: "deneme" })).rejects.toThrow('password authentication failed for user "xyz-user"');
+    await expect(pgStructure({ envPrefix: "DBPX", name: "deneme" })).rejects.toThrow(); // Different pg-version throw different messages.
   });
 });