PgExecArrayParams

Use same parametized query and put Array<T> instead of any T

Example

Inside WHERE part

# Instead of:
# PG::Connection.exec_params(
#   'SELECT * FROM "t1" WHERE "a1" = $1 AND "a3" IN ($4, $5, $6) AND "a2" IN ($2, $3)',
#   [1, 2, 3, "foo", "bar", "baz"]
# )
query = 'select * from t1 where a1 = $1 and a3 = $3 and a2 = $2'
params = [1, [2, 3], ['foo', 'bar', 'baz']]
PgExecArrayParams.exec_array_params(conn, query, params)

Inside SELECT part

# Instead of:
# PG::Connection.exec_params(
#   'SELECT ARRAY[$1, $2]'
#   [1, 2]
# )
PgExecArrayParams.exec_array_params(conn, 'select $1', [[1, 2]])
=> [{"array"=>"{1,2}"}]

Problem

conn.exec_params('select * from users where id IN ($1)', [1,2])
=> PG::IndeterminateDatatype: ERROR:  could not determine data type of parameter $2

conn.exec_params('select * from users where id IN ($1)', [[1,2]])
=> PG::InvalidTextRepresentation: ERROR:  invalid input syntax for integer: "[1, 2]"

Currently you would generate $n parts and flatten params. Or you can inline and embed arrays into query. Don't forget to escape them

Solution

This library encapsulates the first approach in a clean way:

# rewrite query under the hood to
# select * from users where id IN ($1, $2)
PgExecArrayParams.exec_array_params(conn, 'select * from users where id = $1', [[1,2]])
=> [{"id" => 1}, {"id" => 2}]

Batteries

This can also provide more info than plain pg_query gem:

sql = 'with y as (select * from s) select x1, y.y1, z.z as z1 from x join z on z.z = x join y on y.y = x'
PgExecArrayParams::Query.new(sql, []).columns.map(&:name)
=> ['x1', 'y1', 'z1']

Integration with 'pg' gem

PG::Connection.include(PgExecArrayParams) # once in initializer

conn.exec_array_params('select * from users where id = $1', [[1,2]])
=> [{"id" => 1}, {"id" => 2}]

Rails note

ActiveRecord uses the second path (inline + escape).

User.where(age: ["1'; drop table users;", "2"]).to_sql
=> SELECT "users".* FROM "users" WHERE "users"."age" IN ('1''; drop table users;', '2')

It's solid and bulletproof, but

• it must support multiple databases, but non-trivial queries require raw sql chunks anyway
• it's clever, but not so fast as raw pg
• if you're using AR::Relation#to_sql just to handle arrays, consider using this

Benchmark

BENCH_PG_URL='postgres://...' bundle exec ruby benchmark.rb

Comparison:
   exec_array_params:  2150601.0 i/s
        activerecord:    11359.0 i/s - 189.33x  (± 0.00) slower

Comparison:
   exec_array_params:       25.1 i/s
                  pg:       23.6 i/s - same-ish: difference falls within error
  activerecord#pluck:       18.9 i/s - 1.33x  (± 0.00) slower
   activerecord#to_a:        4.4 i/s - 5.67x  (± 0.00) slower