Go version of https://github.com/lfittl/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.
Note that the original Ruby version of this library is much more feature complete.
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
go get github.com/lfittl/pg_query_go
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.
Put the following in a new Go package, after having installed pg_query as above:
package main
import (
"fmt"
"github.com/lfittl/pg_query_go"
)
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:
$ go run main.go
[{"SELECT": {"distinctClause": null, "intoClause": null, "targetList": [{"RESTARGET": {"name": null, "indirection": null, "val": {"A_CONST": {"val": 1, "location": 7}}, "location": 7}}], "fromClause": null, "whereClause": null, "groupClause": null, "havingClause": null, "windowClause": null, "valuesLists": null, "sortClause": null, "limitOffset": null, "limitCount": null, "lockingClause": null, "withClause": null, "op": 0, "all": false, "larg": null, "rarg": null}}]When working with the query information inside Go its recommended you use the Parse() method which returns Go structs:
package main
import (
"fmt"
"reflect"
"github.com/lfittl/pg_query_go"
nodes "github.com/lfittl/pg_query_go/nodes"
)
func main() {
tree, err := pg_query.Parse("SELECT 1")
if err != nil {
panic(err);
}
fmt.Printf("%s\n", reflect.DeepEqual(tree, pg_query.ParsetreeList{
Statements: []nodes.Node{
nodes.SelectStmt{
TargetList: []nodes.Node{
nodes.ResTarget{
Val: nodes.A_Const{
Type: "integer",
Val: nodes.Value{
Type: nodes.T_Integer,
Ival: 1,
},
Location: 7,
},
Location: 7,
},
},
},
},
}));
}You can find all the node struct types in the nodes/ directory.
Put the following in a new Go package, after having installed pg_query as above:
package main
import (
"fmt"
"github.com/lfittl/pg_query_go"
)
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": "found", "datatype": {"PLpgSQL_type": {"typname": "UNKNOWN"}}}}], "action": {"PLpgSQL_stmt_block": {"lineno": 2, "body": [{"PLpgSQL_stmt_if": {"lineno": 3, "cond": {"PLpgSQL_expr": {"query": "SELECT v_version IS NULL"}}, "then_body": [{"PLpgSQL_stmt_return": {"lineno": 4, "expr": {"PLpgSQL_expr": {"query": "SELECT v_name"}}}}]}}, {"PLpgSQL_stmt_return": {"lineno": 6, "expr": {"PLpgSQL_expr": {"query": "SELECT v_name || '/' || v_version"}}}}]}}}}
]As it stands, parsing has considerable overhead for complex queries, due to the use of JSON to pass structs across the C <=> Go barrier.
BenchmarkParseSelect1-4 300000 40723 ns/op 14608 B/op 226 allocs/op
BenchmarkParseSelect2-4 100000 164339 ns/op 49105 B/op 742 allocs/op
BenchmarkParseCreateTable-4 30000 504815 ns/op 149826 B/op 2123 allocs/op
BenchmarkParseSelect1Parallel-4 1000000 12245 ns/op 14608 B/op 226 allocs/op
BenchmarkParseSelect2Parallel-4 300000 46268 ns/op 49105 B/op 742 allocs/op
BenchmarkParseCreateTableParallel-4 100000 157849 ns/op 149827 B/op 2123 allocs/op
A good portion of this is due to JSON parsing inside Go so we can work with Go structs - just the raw parser is 10x faster:
BenchmarkRawParseSelect1-4 5000000 3012 ns/op 192 B/op 2 allocs/op
BenchmarkRawParseSelect2-4 2000000 7755 ns/op 672 B/op 2 allocs/op
BenchmarkRawParseCreateTable-4 1000000 20848 ns/op 2080 B/op 2 allocs/op
BenchmarkRawParseSelect1Parallel-4 20000000 801 ns/op 192 B/op 2 allocs/op
BenchmarkRawParseSelect2Parallel-4 10000000 2220 ns/op 672 B/op 2 allocs/op
BenchmarkRawParseCreateTableParallel-4 2000000 6153 ns/op 2080 B/op 2 allocs/op
Similarly, for query fingerprinting, you might want to use pg_query.FastFingerprint to let the C extension handle it:
BenchmarkFingerprintSelect1-4 300000 42318 ns/op 15564 B/op 246 allocs/op
BenchmarkFingerprintSelect2-4 100000 164205 ns/op 53215 B/op 834 allocs/op
BenchmarkFingerprintCreateTable-4 30000 524524 ns/op 162972 B/op 2371 allocs/op
BenchmarkFastFingerprintSelect1-4 5000000 3614 ns/op 80 B/op 2 allocs/op
BenchmarkFastFingerprintSelect2-4 2000000 6748 ns/op 80 B/op 2 allocs/op
BenchmarkFastFingerprintCreateTable-4 1000000 18361 ns/op 80 B/op 2 allocs/op
Normalization is already handled in the C extension, doesn't depend on JSON parsing at all, and is fast:
BenchmarkNormalizeSelect1-4 10000000 1859 ns/op 24 B/op 2 allocs/op
BenchmarkNormalizeSelect2-4 5000000 3551 ns/op 64 B/op 2 allocs/op
BenchmarkNormalizeCreateTable-4 2000000 6051 ns/op 144 B/op 2 allocs/op
See benchmark_test.go for the queries.
Benchmark numbers from running on a 3.2 GHz Intel Core i5 CPU, OSX 10.11.
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.