miko.gs/pgsql-builder/pkg/structinfo

pgsql-builder

This package generates Postgre SQL queries based on a struct instance. The concept is to define a struct, create a corresponding table to store its instances, and generate queries for managing the rows in that table, such as creating, updating, deleting, and selecting records.

⚠️ The project might be good for small prototyping and showcase of reflection package. It is not recommended to use it in production. Please use a more mature library instead.

The following queries can be generated:

• CREATE TABLE
• DROP TABLE
• INSERT
• UPDATE ... WHERE id = ...
• INSERT ... ON CONFLICT UPDATE ... (upsert)
• SELECT ... WHERE id = ...
• DELETE ... WHERE id = ...
• SELECT ... WHERE ...
• SELECT COUNT(*) WHERE ...
• DELETE ... WHERE ...
• DELETE ... WHERE ... RETURNING id
• UPDATE ... WHERE ...

How to use

TL;DR

Check the code in main_test.go file that contains tests for all use cases.

Defining a struct

Create a struct to define an object to be stored in a database table. In the example below, let's create a Product.

As of now, a field called ID is required. Also, the corresponding table column name that is generated for it is always prefixed with struct name. Hence, for ID field in Product that would be product_id.

There is another field called Flags that could be added, and it treated the same (meaning product_flags is generated, instead of flags).

type Product struct {
  ID int64
  Flags int64
  Name string
  Description string `sql:"type:varchar(2000)"` // "type" is used to force a specific string type for a column
  Code string `sql:"uniq"` // "uniq" tells the module to make this column uniq
  ProductionYear int
  CreatedByUserID int64
  LastModifiedByUserID int64
}

Field tags

In the above definition, a special tag sql is used to add specific configuration for the column when creating a table.

Tag key	Description
uniq	When passed, the column will get a UNIQUE constraint
type	Overwrites default VARCHAR(255) column type for string field. Possible values are: TEXT, BPCHAR(X), CHAR(X), VARCHAR(X), CHARACTER VARYING(X), CHARACTER(X) where X is the size. See PostgreSQL character types for more information.

A different than sql tag can be used by passing TagName in StructSQLOptions{} when calling NewStructSQL function (see below.)

Create a controller for the struct

To generate an SQL query based on a struct, a StructSQL object is used. One per struct.

import (
  sqlbuilder "miko.gs/pgsql-builder"
)

(...)

b := sqlbuilder.New(Product{}, sqlbuilder.Options{})

Options

There are certain options that can be provided to the New function which change the functionality of the object. See the table below.

Key	Type	Description
TableNamePrefix	string	Prefix for the table name, eg. myprefix_
StructName	string	Table name is created out of the struct name, eg. for MyProduct that would be my_product. It is possible to overwrite the struct name, and further table name.
TagName	string	Uses a different tag than sql. It is very useful when another module uses this module.

Get SQL queries

Use any of the following functions to get a desired SQL query.

Function
DropTable()
CreateTable()
Insert()
UpdateByID()
InsertOnConflictUpdate()
SelectByID()
DeleteByID()
Select(order []string, limit int, offset int, filters *Filters)
SelectCount(filters *Filters)
Delete(filters *Filters)
DeleteReturningID(filters *Filters)
Update(values map[string]interface{}, filters *Filters)

Get SQL queries with conditions

It is possible to generate queries such as SELECT, DELETE or UPDATE with conditions based on fields. In the following examples below, all the conditions (called "filters" in the code) are optional - there is no need to pass them.

SELECT

// SELECT * FROM products WHERE (created_by_user_id=$1 AND name=$2) OR (product_year > $3
// AND product_year > $4 AND last_modified_by_user_id IN ($5,$6,$7,$8))
// ORDER BY production_year ASC, name ASC
// LIMIT 100 OFFSET 10
sql := b.Select(
  []string{"ProductionYear", "asc", "Name", "asc"},
  100, 10, 
  &b.Filters{
    "CreatedByUserID": {Op: OpEqual, Val: 4},
    "Name":            {Op: OpEqual, Val: "Magic Sock"},
    Raw: {
      Op: OpOR, 
      Val: []interface{}{
        ".ProductYear > ? AND .ProductYear < ? AND .LastModifiedByUserID(?)",
        // The below values are not important, but the overall number of args must match question marks.
        0,
        0,
        []int{0,0,0,0}, // this list must contain the same number of items as values
      },
    },
  })

SELECT COUNT(*)

// SELECT COUNT(*) AS cnt FROM products WHERE (created_by_user_id=$1 AND name=$2) OR (product_year > $3
// AND product_year > $4 AND last_modified_by_user_id IN ($5,$6,$7,$8))
sql := b.SelectCount(
  &b.Filters{
    "CreatedByUserID": {Op: OpEqual, Val: 4},
    "Name":            {Op: OpEqual, Val: "Magic Sock"},
    Raw: {
      Op: OpOR,
      Val: []interface{}{
        ".ProductYear > ? AND .ProductYear < ? AND .LastModifiedByUserID(?)",
        // The below values are not important, but the overall number of args must match question marks.
        0,
        0,
        []int{0,0,0,0}, // this list must contain the same number of items as values
      },
    },
  })

DELETE

// DELETE FROM products WHERE (created_by_user_id=$1 AND name=$2) OR (product_year > $3
// AND product_year > $4 AND last_modified_by_user_id IN ($5,$6,$7,$8))
sql := b.Delete(
  &b.Filters{
    "CreatedByUserID": {Op: OpEqual, Val: 4},
    "Name": {Op: OpEqual, Val: "Magic Sock"},
    Raw: {
      Op: OpOR,
      Val: []interface{}{
        ".ProductYear > ? AND .ProductYear < ? AND .LastModifiedByUserID(?)",
        // The below values are not important, but the overall number of args must match question marks.
        0,
        0,
        []int
      }{0,0,0,0}, // this list must contain the same number of items as values
    },
  })

UPDATE

// UPDATE products SET production_year=$1, last_modified_by_user_id=$2
// WHERE name LIKE $3;
sql := b.Update(
  map[string]interface{
    "ProductionYear": 1984,
    "LastModifiedByUserID": 13
  },
  &b.Filters{
    Raw: {
      Op: OpAND,
      Val: []interface{} {
        ".Name LIKE ?",
		0,
      },
    },
  })