About optimize result when query

[hdlinh1808]

When I parse this query:
select vpc_id from aws_ec2_instance where not not not vpc_id IS NULL
it returns a lot of bool operator, how I can remove redudant:

{"version":160001,"stmts":[{"stmt":{"SelectStmt":{"targetList":[{"ResTarget":{"val":{"ColumnRef":{"fields":[{"String":{"sval":"vpc_id"}}],"location":7}},"location":7}}],"fromClause":[{"RangeVar":{"relname":"aws_ec2_instance","inh":true,"relpersistence":"p","location":19}}],"whereClause":{"BoolExpr":{"boolop":"NOT_EXPR","args":[{"BoolExpr":{"boolop":"NOT_EXPR","args":[{"BoolExpr":{"boolop":"NOT_EXPR","args":[{"NullTest":{"arg":{"ColumnRef":{"fields":[{"String":{"sval":"vpc_id"}}],"location":54}},"nulltesttype":"IS_NULL","location":61}}],"location":50}}],"location":46}}],"location":42}},"limitOption":"LIMIT_OPTION_DEFAULT","op":"SETOP_NONE"}}}]}

Thanks

[lfittl]

Hi @hdlinh1808!

In order to remove the redundant NOT you would have to modify the parse tree so that the relevant parts are no longer present (I'd suggest comparing with the same query modified to your intended result).

Note that you would have to work with the deserialized version, i.e. Go structs (not JSON), returned by the Parse (not ParseToJSON), modify it and then call Deparse:

pg_query_go/pg_query.go

Line 40 in fdbe27d

func Deparse(tree *ParseResult) (output string, err error) {

[priyanshi-yb]

Hi @lfittl , how to deserialise a JSON string into a GO struct to traverse the Tree returned by ParsePlPgSqlToJSON() ?

[lfittl]

Hi @lfittl , how to deserialise a JSON string into a GO struct to traverse the Tree returned by ParsePlPgSqlToJSON() ?

There is currently no built-in mechanism for that, you'd have to create your own structs and deserialize using Go's JSON functions.