pg_query_go

Go version of https://github.com/pganalyze/pg_query

This Go library and its cgo extension use the actual PostgreSQL server source to parse SQL queries and return the internal PostgreSQL parse tree.

You can find further background to why a query's parse tree is useful here: https://pganalyze.com/blog/parse-postgresql-queries-in-ruby.html

Installation

go get github.com/pganalyze/pg_query_go/v6@latest

Due to compiling parts of PostgreSQL, the first time you build against this library it will take a bit longer.

Expect up to 3 minutes. You can use go build -x to see the progress.

Usage with Go modules

When integrating this library using Go modules, and using a vendor/ directory, you will need to explicitly copy over some of the C build files, since Go does not copy files in subfolders without .go files whilst vendoring.

The best way to do so is to use modvendor, and vendor your modules like this:

go mod vendor
go get -u github.com/goware/modvendor
modvendor -copy="**/*.c **/*.h **/*.proto" -v

Usage

Parsing a query into JSON

Put the following in a new Go package, after having installed pg_query as above:

package main

import (
	"fmt"

	pg_query "github.com/pganalyze/pg_query_go/v6"
)

func main() {
	tree, err := pg_query.ParseToJSON("SELECT 1")
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", tree)
}

Running will output the query's parse tree as JSON:

{"version":160001,"stmts":[{"stmt":{"SelectStmt":{"targetList":[{"ResTarget":{"val":{"A_Const":{"ival":{"ival":1},"location":7}},"location":7}}],"limitOption":"LIMIT_OPTION_DEFAULT","op":"SETOP_NONE"}}}]}

Parsing a query into Go structs

When working with the query information inside Go its recommended you use the Parse() method which returns Go structs:

package main

import (
	"fmt"

	pg_query "github.com/pganalyze/pg_query_go/v6"
)

func main() {
	result, err := pg_query.Parse("SELECT 42")
	if err != nil {
		panic(err)
	}

	// This will output "42"
	fmt.Printf("%d\n", result.Stmts[0].Stmt.GetSelectStmt().GetTargetList()[0].GetResTarget().GetVal().GetAConst().GetIval().Ival)
}

You can find all the node types in the pg_query.pb.go Protobuf definition.

Deparsing a parse tree back into a SQL statement

In order to go back from a parse tree to a SQL statement, you can use the deparsing functionality:

package main

import (
	"fmt"

	pg_query "github.com/pganalyze/pg_query_go/v6"
)

func main() {
	result, err := pg_query.Parse("SELECT 42")
	if err != nil {
		panic(err)
	}

	result.Stmts[0].Stmt.GetSelectStmt().GetTargetList()[0].GetResTarget().Val = pg_query.MakeAConstStrNode("Hello World", -1)

	stmt, err := pg_query.Deparse(result)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", stmt)
}

This will output the following:

SELECT 'Hello World'

Note that it is currently not recommended to pass unsanitized input to the deparser, as it may lead to crashes.

Parsing a PL/pgSQL function into JSON (Experimental)

Put the following in a new Go package, after having installed pg_query as above:

package main

import (
	"fmt"

	pg_query "github.com/pganalyze/pg_query_go/v6"
)

func main() {
	tree, err := pg_query.ParsePlPgSqlToJSON(
		`CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name varchar, v_version varchar)
  			RETURNS varchar AS $$
  			BEGIN
  			    IF v_version IS NULL THEN
  			        RETURN v_name;
  			    END IF;
  			    RETURN v_name || '/' || v_version;
  			END;
  			$$ LANGUAGE plpgsql;`)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", tree)
}

Running will output the functions's parse tree as JSON:

$ go run main.go
[
{"PLpgSQL_function":{"datums":[{"PLpgSQL_var":{"refname":"v_name","datatype":{"PLpgSQL_type":{"typname":"UNKNOWN"}}}},{"PLpgSQL_var":{"refname":"v_version","datatype":{"PLpgSQL_type":{"typname":"UNKNOWN"}}}},{"PLpgSQL_var":{"refname":"found","datatype":{"PLpgSQL_type":{"typname":"UNKNOWN"}}}}],"action":{"PLpgSQL_stmt_block":{"lineno":2,"body":[{"PLpgSQL_stmt_if":{"lineno":3,"cond":{"PLpgSQL_expr":{"query":"v_version IS NULL"}},"then_body":[{"PLpgSQL_stmt_return":{"lineno":4,"expr":{"PLpgSQL_expr":{"query":"v_name"}}}}]}},{"PLpgSQL_stmt_return":{"lineno":6,"expr":{"PLpgSQL_expr":{"query":"v_name || '/' || v_version"}}}}]}}}}
]

Benchmarks

$ make benchmark
go build -a
go test -test.bench=. -test.run=XXX -test.benchtime 10s -test.benchmem -test.cpu=4
goos: darwin
goarch: arm64
pkg: github.com/pganalyze/pg_query_go/v6
BenchmarkParseSelect1-4                          2874156              4186 ns/op            1040 B/op         18 allocs/op
BenchmarkParseSelect2-4                           824781             14572 ns/op            2832 B/op         57 allocs/op
BenchmarkParseCreateTable-4                       351037             34591 ns/op            8480 B/op        149 allocs/op
BenchmarkParseSelect1Parallel-4                  9027080              1320 ns/op            1040 B/op         18 allocs/op
BenchmarkParseSelect2Parallel-4                  2745390              4369 ns/op            2832 B/op         57 allocs/op
BenchmarkParseCreateTableParallel-4              1000000             10487 ns/op            8480 B/op        149 allocs/op
BenchmarkRawParseSelect1-4                       3778771              3183 ns/op             128 B/op          3 allocs/op
BenchmarkRawParseSelect2-4                       1000000             10985 ns/op             288 B/op          3 allocs/op
BenchmarkRawParseCreateTable-4                    460714             26397 ns/op            1056 B/op          3 allocs/op
BenchmarkRawParseSelect1Parallel-4              13338790               902.7 ns/op           128 B/op          3 allocs/op
BenchmarkRawParseSelect2Parallel-4               4060762              2956 ns/op             288 B/op          3 allocs/op
BenchmarkRawParseCreateTableParallel-4           1709883              7001 ns/op            1056 B/op          3 allocs/op
BenchmarkFingerprintSelect1-4                    6394882              1875 ns/op              48 B/op          2 allocs/op
BenchmarkFingerprintSelect2-4                    2865390              4174 ns/op              48 B/op          2 allocs/op
BenchmarkFingerprintCreateTable-4                1688920              7143 ns/op              48 B/op          2 allocs/op
BenchmarkNormalizeSelect1-4                     10604962              1133 ns/op              32 B/op          2 allocs/op
BenchmarkNormalizeSelect2-4                      6226136              1938 ns/op              64 B/op          2 allocs/op
BenchmarkNormalizeCreateTable-4                  4542387              2635 ns/op             144 B/op          2 allocs/op
PASS
ok      github.com/pganalyze/pg_query_go/v6     258.376s

Note that allocation counts exclude the cgo portion, so they are higher than shown here.

See benchmark_test.go for details on the benchmarks.

Authors

• Lukas Fittl

License

Copyright (c) 2015, Lukas Fittl lukas@fittl.com
pg_query_go is licensed under the 3-clause BSD license, see LICENSE file for details.

This project includes code derived from the PostgreSQL project, see LICENSE.POSTGRESQL for details.