knex-schema-inspector/lib/dialects/postgres.ts

Utility for extracting information about existing DB schema

import { Knex } from 'knex';
import { SchemaInspector } from '../types/schema-inspector';
import { Table } from '../types/table';
import { Column } from '../types/column';
import { stripQuotes } from '../utils/strip-quotes';

type RawColumn = {
  name: string;
  table: string;
  schema: string;
  data_type: string;
  is_nullable: boolean;
  generation_expression: null | string;
  default_value: null | string;
  is_generated: boolean;
  max_length: null | number;
  comment: null | string;
  numeric_precision: null | number;
  numeric_scale: null | number;
};

type Constraint = {
  type: 'f' | 'p' | 'u';
  table: string;
  column: string;
  foreign_key_schema: null | string;
  foreign_key_table: null | string;
  foreign_key_column: null | string;
  has_auto_increment: null | boolean;
};

/**
 * Converts Postgres default value to JS
 * Eg `'example'::character varying` => `example`
 */
export function parseDefaultValue(value: string | null) {
  if (value === null) return null;
  if (value.startsWith('nextval(')) return value;

  value = value.split('::')[0];

  if (value.trim().toLowerCase() === 'null') return null;

  return stripQuotes(value);
}

export default class Postgres implements SchemaInspector {
  knex: Knex;
  schema: string;
  explodedSchema: string[];

  constructor(knex: Knex) {
    this.knex = knex;
    const config = knex.client.config;
    if (!config.searchPath) {
      this.schema = 'public';
      this.explodedSchema = [this.schema];
    } else if (typeof config.searchPath === 'string') {
      this.schema = config.searchPath;
      this.explodedSchema = [config.searchPath];
    } else {
      this.schema = config.searchPath[0];
      this.explodedSchema = config.searchPath;
    }
  }

  // Postgres specific
  // ===============================================================================================

  /**
   * Set the schema to be used in other methods
   */
  withSchema(schema: string) {
    this.schema = schema;
    this.explodedSchema = [this.schema];
    return this;
  }

  // Tables
  // ===============================================================================================

  /**
   * List all existing tables in the current schema/database
   */
  async tables() {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const result = await this.knex.raw(
      `
      SELECT
        rel.relname AS name
      FROM
        pg_class rel
      WHERE
        rel.relnamespace IN (${schemaIn})
        AND rel.relkind = 'r'
      ORDER BY rel.relname
    `
    );

    return result.rows.map((row: { name: string }) => row.name);
  }

  /**
   * Get the table info for a given table. If table parameter is undefined, it will return all tables
   * in the current schema/database
   */
  tableInfo(): Promise<Table[]>;
  tableInfo(table: string): Promise<Table>;
  async tableInfo(table?: string) {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const bindings: any[] = [];
    if (table) bindings.push(table);

    const result = await this.knex.raw(
      `
      SELECT
        rel.relnamespace::regnamespace::text AS schema,
        rel.relname AS name,
        des.description AS comment
      FROM
        pg_class rel
      LEFT JOIN pg_description des ON rel.oid = des.objoid AND des.objsubid = 0
      WHERE
        rel.relnamespace IN (${schemaIn})
        ${table ? 'AND rel.relname = ?' : ''}
        AND rel.relkind = 'r'
      ORDER BY rel.relname
    `,
      bindings
    );

    if (table) return result.rows[0];
    return result.rows;
  }

  /**
   * Check if a table exists in the current schema/database
   */
  async hasTable(table: string) {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const result = await this.knex.raw(
      `
      SELECT
        rel.relname AS name
      FROM
        pg_class rel
      WHERE
        rel.relnamespace IN (${schemaIn})
        AND rel.relkind = 'r'
        AND rel.relname = ?
      ORDER BY rel.relname
    `,
      [table]
    );

    return result.rows.length > 0;
  }

  // Columns
  // ===============================================================================================

  /**
   * Get all the available columns in the current schema/database. Can be filtered to a specific table
   */
  async columns(table?: string) {
    const bindings: any[] = [];
    if (table) bindings.push(table);

    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const result = await this.knex.raw(
      `
      SELECT
        att.attname AS column,
        rel.relname AS table
      FROM
        pg_attribute att
        LEFT JOIN pg_class rel ON att.attrelid = rel.oid
      WHERE
        rel.relnamespace IN (${schemaIn})
        ${table ? 'AND rel.relname = ?' : ''}
        AND rel.relkind = 'r'
        AND att.attnum > 0
        AND NOT att.attisdropped;
    `,
      bindings
    );

    return result.rows;
  }

  /**
   * Get the column info for all columns, columns in a given table, or a specific column.
   */
  columnInfo(): Promise<Column[]>;
  columnInfo(table: string): Promise<Column[]>;
  columnInfo(table: string, column: string): Promise<Column>;
  async columnInfo<T>(table?: string, column?: string) {
    const { knex } = this;

    const bindings: any[] = [];
    if (table) bindings.push(table);
    if (column) bindings.push(column);

    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const versionResponse = await this.knex.raw(`SHOW server_version`);

    const majorVersion =
      versionResponse.rows?.[0]?.server_version?.split('.')?.[0] ?? 10;

    let generationSelect = `
      NULL AS generation_expression,
      pg_get_expr(ad.adbin, ad.adrelid) AS default_value,
      FALSE AS is_generated,
    `;

    if (Number(majorVersion) >= 12) {
      generationSelect = `
        CASE WHEN att.attgenerated = 's' THEN pg_get_expr(ad.adbin, ad.adrelid) ELSE null END AS generation_expression,
        CASE WHEN att.attgenerated = '' THEN pg_get_expr(ad.adbin, ad.adrelid) ELSE null END AS default_value,
        att.attgenerated = 's' AS is_generated,
      `;
    }

    const [columns, constraints] = await Promise.all([
      knex.raw<{ rows: RawColumn[] }>(
        `
        SELECT
        	att.attname AS name,
          rel.relname AS table,
          rel.relnamespace::regnamespace::text as schema,
          att.atttypid::regtype::text AS data_type,
          NOT att.attnotnull AS is_nullable,
          ${generationSelect}
          CASE
            WHEN att.atttypid IN (1042, 1043) THEN (att.atttypmod - 4)::int4
            WHEN att.atttypid IN (1560, 1562) THEN (att.atttypmod)::int4
            ELSE NULL
          END AS max_length,
          des.description AS comment,
          CASE att.atttypid
            WHEN 21 THEN 16
            WHEN 23 THEN 32
            WHEN 20 THEN 64
            WHEN 1700 THEN
              CASE WHEN atttypmod = -1 THEN NULL
                ELSE (((atttypmod - 4) >> 16) & 65535)::int4
              END
            WHEN 700 THEN 24
            WHEN 701 THEN 53
            ELSE NULL
          END AS numeric_precision,
          CASE
            WHEN atttypid IN (21, 23, 20) THEN 0
            WHEN atttypid = 1700 THEN
              CASE
                WHEN atttypmod = -1 THEN NULL
                ELSE ((atttypmod - 4) & 65535)::int4
              END
            ELSE null
          END AS numeric_scale
        FROM
          pg_attribute att
          LEFT JOIN pg_class rel ON att.attrelid = rel.oid
          LEFT JOIN pg_attrdef ad ON (att.attrelid, att.attnum) = (ad.adrelid, ad.adnum)
          LEFT JOIN pg_description des ON (att.attrelid, att.attnum) = (des.objoid, des.objsubid)
        WHERE
          rel.relnamespace IN (${schemaIn})
          ${table ? 'AND rel.relname = ?' : ''}
          ${column ? 'AND att.attname = ?' : ''}
          AND rel.relkind = 'r'
          AND att.attnum > 0
          AND NOT att.attisdropped
        ORDER BY rel.relname, att.attnum;
      `,
        bindings
      ),
      knex.raw<{ rows: Constraint[] }>(
        `
        SELECT
          con.contype AS type,
          rel.relname AS table,
          att.attname AS column,
          frel.relnamespace::regnamespace::text AS foreign_key_schema,
          frel.relname AS foreign_key_table,
          fatt.attname AS foreign_key_column,
          CASE
            WHEN con.contype = 'p' THEN pg_get_serial_sequence(att.attrelid::regclass::text, att.attname) != ''
            ELSE NULL
          END AS has_auto_increment
        FROM
          pg_constraint con
        LEFT JOIN pg_class rel ON con.conrelid = rel.oid
        LEFT JOIN pg_class frel ON con.confrelid = frel.oid
        LEFT JOIN pg_attribute att ON att.attrelid = con.conrelid AND att.attnum = con.conkey[1]
        LEFT JOIN pg_attribute fatt ON fatt.attrelid = con.confrelid AND fatt.attnum = con.confkey[1]
        WHERE con.connamespace IN (${schemaIn})
          AND array_length(con.conkey, 1) <= 1
          AND (con.confkey IS NULL OR array_length(con.confkey, 1) = 1)
          ${table ? 'AND rel.relname = ?' : ''}
          ${column ? 'AND att.attname = ?' : ''}
        `,
        bindings
      ),
    ]);

    const parsedColumms: Column[] = columns.rows.map((col): Column => {
      const constraintsForColumn = constraints.rows.filter(
        (constraint) =>
          constraint.table === col.table && constraint.column === col.name
      );

      const foreignKeyConstraint = constraintsForColumn.find(
        (constraint) => constraint.type === 'f'
      );

      return {
        ...col,
        is_unique: constraintsForColumn.some((constraint) =>
          ['u', 'p'].includes(constraint.type)
        ),
        is_primary_key: constraintsForColumn.some(
          (constraint) => constraint.type === 'p'
        ),
        has_auto_increment: constraintsForColumn.some(
          (constraint) => constraint.has_auto_increment
        ),
        default_value: parseDefaultValue(col.default_value),
        foreign_key_schema: foreignKeyConstraint?.foreign_key_schema ?? null,
        foreign_key_table: foreignKeyConstraint?.foreign_key_table ?? null,
        foreign_key_column: foreignKeyConstraint?.foreign_key_column ?? null,
      };
    });

    if (table && column) return parsedColumms[0];
    return parsedColumms;
  }

  /**
   * Check if the given table contains the given column
   */
  async hasColumn(table: string, column: string) {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const result = await this.knex.raw(
      `
      SELECT
        att.attname AS column,
        rel.relname AS table
      FROM
        pg_attribute att
        LEFT JOIN pg_class rel ON att.attrelid = rel.oid
      WHERE
        rel.relnamespace IN (${schemaIn})
        AND rel.relname = ?
        AND att.attname = ?
        AND rel.relkind = 'r'
        AND att.attnum > 0
        AND NOT att.attisdropped;
    `,
      [table, column]
    );

    return result.rows;
  }

  /**
   * Get the primary key column for the given table
   */
  async primary(table: string): Promise<string | null> {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const result = await this.knex.raw(
      `
      SELECT
          att.attname AS column
        FROM
          pg_constraint con
        LEFT JOIN pg_class rel ON con.conrelid = rel.oid
        LEFT JOIN pg_attribute att ON att.attrelid = con.conrelid AND att.attnum = con.conkey[1]
        WHERE con.connamespace IN (${schemaIn})
          AND con.contype = 'p'
          AND array_length(con.conkey, 1) <= 1
          AND rel.relname = ?
    `,
      [table]
    );

    return result.rows?.[0]?.column ?? null;
  }

  // Foreign Keys
  // ===============================================================================================

  async foreignKeys(table?: string) {
    const schemaIn = this.explodedSchema.map(
      (schemaName) => `${this.knex.raw('?', [schemaName])}::regnamespace`
    );

    const bindings: any[] = [];
    if (table) bindings.push(table);

    const result = await this.knex.raw(
      `
       SELECT
          con.conname AS constraint_name,
          rel.relname AS table,
          att.attname AS column,
          frel.relnamespace::regnamespace::text AS foreign_key_schema,
          frel.relname AS foreign_key_table,
          fatt.attname AS foreign_key_column,
          CASE con.confupdtype
            WHEN 'r' THEN
              'RESTRICT'
            WHEN 'c' THEN
              'CASCADE'
            WHEN 'n' THEN
              'SET NULL'
            WHEN 'd' THEN
              'SET DEFAULT'
            WHEN 'a' THEN
              'NO ACTION'
            ELSE
              NULL
          END AS on_update,
          CASE con.confdeltype
            WHEN 'r' THEN
              'RESTRICT'
            WHEN 'c' THEN
              'CASCADE'
            WHEN 'n' THEN
              'SET NULL'
            WHEN 'd' THEN
              'SET DEFAULT'
            WHEN 'a' THEN
              'NO ACTION'
            ELSE
              NULL
          END AS on_delete
        FROM
          pg_constraint con
        LEFT JOIN pg_class rel ON con.conrelid = rel.oid
        LEFT JOIN pg_class frel ON con.confrelid = frel.oid
        LEFT JOIN pg_attribute att ON att.attrelid = con.conrelid AND att.attnum = con.conkey[1]
        LEFT JOIN pg_attribute fatt ON fatt.attrelid = con.confrelid AND fatt.attnum = con.confkey[1]
        WHERE con.connamespace IN (${schemaIn})
          AND array_length(con.conkey, 1) <= 1
          AND (con.confkey IS NULL OR array_length(con.confkey, 1) = 1)
          AND con.contype = 'f'
          ${table ? 'AND rel.relname = ?' : ''}
    `,
      bindings
    );

    return result.rows;
  }
}