PgQuery.parse("SELECT 1")

=> #<PgQuery:0x007fe92b27ea18
 @tree=
  [{"SelectStmt"=>
     {"targetList"=>
       [{"ResTarget"=>
          {"val"=>{"A_Const"=>{"val"=>{"Integer"=>{"ival"=>1}}, "location"=>7}},
           "location"=>7}}],
      "op"=>0,
  }}],
 @query="SELECT 1",
 @warnings=[]>

parsed_query = PgQuery.parse("SELECT * FROM users")

=> #<PgQuery:0x007ff3e956c8b0
 @tree=
  [{"SelectStmt"=>
    {"targetList"=>
      [{"ResTarget"=>
        {"val"=>
          {"ColumnRef"=> {"fields"=>[{"A_Star"=>{}}], "location"=>7}},
         "location"=>7}
      }],
     "fromClause"=>
      [{"RangeVar"=>
        {"relname"=>"users",
         "inhOpt"=>2,
         "relpersistence"=>"p",
         "location"=>14}}],
   }}],
 @query="SELECT * FROM users",
 @warnings=[]>

# Modify the parse tree in some way
parsed_query.tree[0]['SelectStmt']['fromClause'][0]['RangeVar']['relname'] = 'other_users'

# Turn it into SQL again
parsed_query.deparse
=> "SELECT * FROM \"other_users\""

# Normalizing a query (like pg_stat_statements in Postgres 10+)
PgQuery.normalize("SELECT 1 FROM x WHERE y = 'foo'")

=> "SELECT $1 FROM x WHERE y = $2"

# Parsing a normalized query (pre-Postgres 10 style)
PgQuery.parse("SELECT ? FROM x WHERE y = ?")

=> #<PgQuery:0x007fb99455a438
 @tree=
  [{"SelectStmt"=>
     {"targetList"=>
       [{"ResTarget"=>
          {"val"=>{"ParamRef"=>{"location"=>7}},
           "location"=>7}}],
      "fromClause"=>
       [{"RangeVar"=>
          {"relname"=>"x",
           "inhOpt"=>2,
           "relpersistence"=>"p",
           "location"=>14}}],
      "whereClause"=>
       {"A_Expr"=>
         {"kind"=>0,
          "name"=>[{"String"=>{"str"=>"="}}],
          "lexpr"=>{"ColumnRef"=>{"fields"=>[{"String"=>{"str"=>"y"}}], "location"=>22}},
          "rexpr"=>{"ParamRef"=>{"location"=>26}},
          "location"=>24}},
  }}],
 @query="SELECT ? FROM x WHERE y = ?",
 @warnings=[]>

PgQuery.parse("SELECT ? FROM x JOIN y USING (id) WHERE z = ?").tables

=> ["x", "y"]

PgQuery.parse("SELECT ? FROM x WHERE x.y = ? AND z = ?").filter_columns

=> [["x", "y"], [nil, "z"]]

PgQuery.parse("SELECT 1").fingerprint

=> "8e1acac181c6d28f4a923392cf1c4eda49ee4cd2"

PgQuery.parse("SELECT 2; --- comment").fingerprint

=> "8e1acac181c6d28f4a923392cf1c4eda49ee4cd2"

# Faster fingerprint method that is implemented inside the native library
PgQuery.fingerprint("SELECT ?")

=> "8e1acac181c6d28f4a923392cf1c4eda49ee4cd2"