From bd157290f6eca176a208ba5ab2c0b19b75671351 Mon Sep 17 00:00:00 2001
From: Vikram Rangnekar <vicram@gmail.com>
Date: Thu, 4 Jun 2020 21:55:52 -0400
Subject: [PATCH] fix: bug with parsing variables in roles_query

---
 core/args.go                      |  5 +-
 core/build.go                     | 13 +++--
 core/core.go                      |  2 +-
 core/init.go                      | 19 +++++--
 core/internal/psql/columns.go     | 39 +++++++-------
 core/internal/psql/insert.go      |  2 +-
 core/internal/psql/metadata.go    | 61 ++++++++++++++++++++++
 core/internal/psql/mutate.go      |  4 +-
 core/internal/psql/query.go       | 86 ++++++++-----------------------
 core/internal/psql/update.go      |  2 +-
 core/internal/qcode/parse_test.go | 19 ++++++-
 core/prepare.go                   |  2 +-
 core/remote.go                    |  8 +--
 core/resolve.go                   |  2 +-
 jsn/filter.go                     |  4 +-
 jsn/get.go                        |  4 +-
 16 files changed, 159 insertions(+), 113 deletions(-)
 create mode 100644 core/internal/psql/metadata.go

diff --git a/core/args.go b/core/args.go
index 9a309f6..ab9b473 100644
--- a/core/args.go
+++ b/core/args.go
@@ -12,7 +12,8 @@ import (
 // to a prepared statement.
 
 func (c *scontext) argList(md psql.Metadata) ([]interface{}, error) {
-	vars := make([]interface{}, len(md.Params))
+	params := md.Params()
+	vars := make([]interface{}, len(params))
 
 	var fields map[string]json.RawMessage
 	var err error
@@ -25,7 +26,7 @@ func (c *scontext) argList(md psql.Metadata) ([]interface{}, error) {
 		}
 	}
 
-	for i, p := range md.Params {
+	for i, p := range params {
 		switch p.Name {
 		case "user_id":
 			if v := c.Value(UserIDKey); v != nil {
diff --git a/core/build.go b/core/build.go
index 9089235..a24cda9 100644
--- a/core/build.go
+++ b/core/build.go
@@ -88,6 +88,7 @@ func (sg *SuperGraph) buildMultiStmt(query, vars []byte) ([]stmt, error) {
 
 	stmts := make([]stmt, 0, len(sg.conf.Roles))
 	w := &bytes.Buffer{}
+	md := psql.Metadata{}
 
 	for i := 0; i < len(sg.conf.Roles); i++ {
 		role := &sg.conf.Roles[i]
@@ -105,16 +106,18 @@ func (sg *SuperGraph) buildMultiStmt(query, vars []byte) ([]stmt, error) {
 		stmts = append(stmts, stmt{role: role, qc: qc})
 		s := &stmts[len(stmts)-1]
 
-		s.md, err = sg.pc.Compile(w, qc, psql.Variables(vm))
+		md, err = sg.pc.CompileWithMetadata(w, qc, psql.Variables(vm), md)
 		if err != nil {
 			return nil, err
 		}
 
 		s.sql = w.String()
+		s.md = md
+
 		w.Reset()
 	}
 
-	sql, err := sg.renderUserQuery(stmts)
+	sql, err := sg.renderUserQuery(md, stmts)
 	if err != nil {
 		return nil, err
 	}
@@ -124,7 +127,7 @@ func (sg *SuperGraph) buildMultiStmt(query, vars []byte) ([]stmt, error) {
 }
 
 //nolint: errcheck
-func (sg *SuperGraph) renderUserQuery(stmts []stmt) (string, error) {
+func (sg *SuperGraph) renderUserQuery(md psql.Metadata, stmts []stmt) (string, error) {
 	w := &bytes.Buffer{}
 
 	io.WriteString(w, `SELECT "_sg_auth_info"."role", (CASE "_sg_auth_info"."role" `)
@@ -142,7 +145,7 @@ func (sg *SuperGraph) renderUserQuery(stmts []stmt) (string, error) {
 	}
 
 	io.WriteString(w, `END) FROM (SELECT (CASE WHEN EXISTS (`)
-	io.WriteString(w, sg.conf.RolesQuery)
+	md.RenderVar(w, sg.conf.RolesQuery)
 	io.WriteString(w, `) THEN `)
 
 	io.WriteString(w, `(SELECT (CASE`)
@@ -158,7 +161,7 @@ func (sg *SuperGraph) renderUserQuery(stmts []stmt) (string, error) {
 	}
 
 	io.WriteString(w, ` ELSE 'user' END) FROM (`)
-	io.WriteString(w, sg.conf.RolesQuery)
+	md.RenderVar(w, sg.conf.RolesQuery)
 	io.WriteString(w, `) AS "_sg_auth_roles_query" LIMIT 1) `)
 	io.WriteString(w, `ELSE 'anon' END) FROM (VALUES (1)) AS "_sg_auth_filler") AS "_sg_auth_info"(role) LIMIT 1; `)
 
diff --git a/core/core.go b/core/core.go
index 9c9d7f3..31df8d2 100644
--- a/core/core.go
+++ b/core/core.go
@@ -125,7 +125,7 @@ func (c *scontext) execQuery() ([]byte, error) {
 		return nil, err
 	}
 
-	if len(data) == 0 || st.md.Skipped == 0 {
+	if len(data) == 0 || st.md.Skipped() == 0 {
 		return data, nil
 	}
 
diff --git a/core/init.go b/core/init.go
index fddb1b4..a464ef0 100644
--- a/core/init.go
+++ b/core/init.go
@@ -75,13 +75,22 @@ func (sg *SuperGraph) initConfig() error {
 
 	if c.RolesQuery == "" {
 		sg.log.Printf("INF roles_query not defined: attribute based access control disabled")
+	} else {
+		n := 0
+		for k, v := range sg.roles {
+			if k == "user" || k == "anon" {
+				n++
+			} else if v.Match != "" {
+				n++
+			}
+		}
+		sg.abacEnabled = (n > 2)
+
+		if !sg.abacEnabled {
+			sg.log.Printf("WRN attribute based access control disabled: no custom roles found (with 'match' defined)")
+		}
 	}
 
-	_, userExists := sg.roles["user"]
-	_, sg.anonExists = sg.roles["anon"]
-
-	sg.abacEnabled = userExists && c.RolesQuery != ""
-
 	return nil
 }
 
diff --git a/core/internal/psql/columns.go b/core/internal/psql/columns.go
index d339dc9..73148fc 100644
--- a/core/internal/psql/columns.go
+++ b/core/internal/psql/columns.go
@@ -1,4 +1,3 @@
-//nolint:errcheck
 package psql
 
 import (
@@ -112,15 +111,15 @@ func (c *compilerContext) renderColumnSearchRank(sel *qcode.Select, ti *DBTableI
 	c.renderComma(columnsRendered)
 	//fmt.Fprintf(w, `ts_rank("%s"."%s", websearch_to_tsquery('%s')) AS %s`,
 	//c.sel.Name, cn, arg.Val, col.Name)
-	io.WriteString(c.w, `ts_rank(`)
+	_, _ = io.WriteString(c.w, `ts_rank(`)
 	colWithTable(c.w, ti.Name, cn)
 	if c.schema.ver >= 110000 {
-		io.WriteString(c.w, `, websearch_to_tsquery(`)
+		_, _ = io.WriteString(c.w, `, websearch_to_tsquery(`)
 	} else {
-		io.WriteString(c.w, `, to_tsquery(`)
+		_, _ = io.WriteString(c.w, `, to_tsquery(`)
 	}
-	c.renderValueExp(Param{Name: arg.Val, Type: "string"})
-	io.WriteString(c.w, `))`)
+	c.md.renderValueExp(c.w, Param{Name: arg.Val, Type: "string"})
+	_, _ = io.WriteString(c.w, `))`)
 	alias(c.w, col.Name)
 
 	return nil
@@ -137,15 +136,15 @@ func (c *compilerContext) renderColumnSearchHeadline(sel *qcode.Select, ti *DBTa
 	c.renderComma(columnsRendered)
 	//fmt.Fprintf(w, `ts_headline("%s"."%s", websearch_to_tsquery('%s')) AS %s`,
 	//c.sel.Name, cn, arg.Val, col.Name)
-	io.WriteString(c.w, `ts_headline(`)
+	_, _ = io.WriteString(c.w, `ts_headline(`)
 	colWithTable(c.w, ti.Name, cn)
 	if c.schema.ver >= 110000 {
-		io.WriteString(c.w, `, websearch_to_tsquery(`)
+		_, _ = io.WriteString(c.w, `, websearch_to_tsquery(`)
 	} else {
-		io.WriteString(c.w, `, to_tsquery(`)
+		_, _ = io.WriteString(c.w, `, to_tsquery(`)
 	}
-	c.renderValueExp(Param{Name: arg.Val, Type: "string"})
-	io.WriteString(c.w, `))`)
+	c.md.renderValueExp(c.w, Param{Name: arg.Val, Type: "string"})
+	_, _ = io.WriteString(c.w, `))`)
 	alias(c.w, col.Name)
 
 	return nil
@@ -157,9 +156,9 @@ func (c *compilerContext) renderColumnTypename(sel *qcode.Select, ti *DBTableInf
 	}
 
 	c.renderComma(columnsRendered)
-	io.WriteString(c.w, `(`)
+	_, _ = io.WriteString(c.w, `(`)
 	squoted(c.w, ti.Name)
-	io.WriteString(c.w, ` :: text)`)
+	_, _ = io.WriteString(c.w, ` :: text)`)
 	alias(c.w, col.Name)
 
 	return nil
@@ -169,9 +168,9 @@ func (c *compilerContext) renderColumnFunction(sel *qcode.Select, ti *DBTableInf
 	pl := funcPrefixLen(c.schema.fm, col.Name)
 	// if pl == 0 {
 	// 	//fmt.Fprintf(w, `'%s not defined' AS %s`, cn, col.Name)
-	// 	io.WriteString(c.w, `'`)
-	// 	io.WriteString(c.w, col.Name)
-	// 	io.WriteString(c.w, ` not defined'`)
+	// 	_, _ = io.WriteString(c.w, `'`)
+	// 	_, _ = io.WriteString(c.w, col.Name)
+	// 	_, _ = io.WriteString(c.w, ` not defined'`)
 	// 	alias(c.w, col.Name)
 	// }
 
@@ -190,10 +189,10 @@ func (c *compilerContext) renderColumnFunction(sel *qcode.Select, ti *DBTableInf
 	c.renderComma(columnsRendered)
 
 	//fmt.Fprintf(w, `%s("%s"."%s") AS %s`, fn, c.sel.Name, cn, col.Name)
-	io.WriteString(c.w, fn)
-	io.WriteString(c.w, `(`)
+	_, _ = io.WriteString(c.w, fn)
+	_, _ = io.WriteString(c.w, `(`)
 	colWithTable(c.w, ti.Name, cn)
-	io.WriteString(c.w, `)`)
+	_, _ = io.WriteString(c.w, `)`)
 	alias(c.w, col.Name)
 
 	return nil
@@ -201,7 +200,7 @@ func (c *compilerContext) renderColumnFunction(sel *qcode.Select, ti *DBTableInf
 
 func (c *compilerContext) renderComma(columnsRendered int) {
 	if columnsRendered != 0 {
-		io.WriteString(c.w, `, `)
+		_, _ = io.WriteString(c.w, `, `)
 	}
 }
 
diff --git a/core/internal/psql/insert.go b/core/internal/psql/insert.go
index 21dc243..48d1a2c 100644
--- a/core/internal/psql/insert.go
+++ b/core/internal/psql/insert.go
@@ -25,7 +25,7 @@ func (c *compilerContext) renderInsert(
 	if insert[0] == '[' {
 		io.WriteString(c.w, `json_array_elements(`)
 	}
-	c.renderValueExp(Param{Name: qc.ActionVar, Type: "json"})
+	c.md.renderValueExp(c.w, Param{Name: qc.ActionVar, Type: "json"})
 	io.WriteString(c.w, ` :: json`)
 	if insert[0] == '[' {
 		io.WriteString(c.w, `)`)
diff --git a/core/internal/psql/metadata.go b/core/internal/psql/metadata.go
new file mode 100644
index 0000000..e8d8bfe
--- /dev/null
+++ b/core/internal/psql/metadata.go
@@ -0,0 +1,61 @@
+package psql
+
+import (
+	"io"
+)
+
+func (md *Metadata) RenderVar(w io.Writer, vv string) {
+	f, s := -1, 0
+
+	for i := range vv {
+		v := vv[i]
+		switch {
+		case (i > 0 && vv[i-1] != '\\' && v == '$') || v == '$':
+			if (i - s) > 0 {
+				_, _ = io.WriteString(w, vv[s:i])
+			}
+			f = i
+
+		case (v < 'a' && v > 'z') &&
+			(v < 'A' && v > 'Z') &&
+			(v < '0' && v > '9') &&
+			v != '_' &&
+			f != -1 &&
+			(i-f) > 1:
+			md.renderValueExp(w, Param{Name: vv[f+1 : i]})
+			s = i
+			f = -1
+		}
+	}
+
+	if f != -1 && (len(vv)-f) > 1 {
+		md.renderValueExp(w, Param{Name: vv[f+1:]})
+	} else {
+		_, _ = io.WriteString(w, vv[s:])
+	}
+}
+
+func (md *Metadata) renderValueExp(w io.Writer, p Param) {
+	_, _ = io.WriteString(w, `$`)
+	if v, ok := md.pindex[p.Name]; ok {
+		int32String(w, int32(v))
+
+	} else {
+		md.params = append(md.params, p)
+		n := len(md.params)
+
+		if md.pindex == nil {
+			md.pindex = make(map[string]int)
+		}
+		md.pindex[p.Name] = n
+		int32String(w, int32(n))
+	}
+}
+
+func (md Metadata) Skipped() uint32 {
+	return md.skipped
+}
+
+func (md Metadata) Params() []Param {
+	return md.params
+}
diff --git a/core/internal/psql/mutate.go b/core/internal/psql/mutate.go
index f23dae4..e5023b3 100644
--- a/core/internal/psql/mutate.go
+++ b/core/internal/psql/mutate.go
@@ -432,11 +432,11 @@ func (c *compilerContext) renderInsertUpdateColumns(
 			val := root.PresetMap[cn]
 			switch {
 			case ok && len(val) > 1 && val[0] == '$':
-				c.renderValueExp(Param{Name: val[1:], Type: col.Type})
+				c.md.renderValueExp(c.w, Param{Name: val[1:], Type: col.Type})
 
 			case ok && strings.HasPrefix(val, "sql:"):
 				io.WriteString(c.w, `(`)
-				c.renderVar(val[4:], c.renderValueExp)
+				c.md.RenderVar(c.w, val[4:])
 				io.WriteString(c.w, `)`)
 
 			case ok:
diff --git a/core/internal/psql/query.go b/core/internal/psql/query.go
index 5824933..77ee4eb 100644
--- a/core/internal/psql/query.go
+++ b/core/internal/psql/query.go
@@ -25,8 +25,8 @@ type Param struct {
 }
 
 type Metadata struct {
-	Skipped uint32
-	Params  []Param
+	skipped uint32
+	params  []Param
 	pindex  map[string]int
 }
 
@@ -80,26 +80,30 @@ func (co *Compiler) CompileEx(qc *qcode.QCode, vars Variables) (Metadata, []byte
 }
 
 func (co *Compiler) Compile(w io.Writer, qc *qcode.QCode, vars Variables) (Metadata, error) {
+	return co.CompileWithMetadata(w, qc, vars, Metadata{})
+}
+
+func (co *Compiler) CompileWithMetadata(w io.Writer, qc *qcode.QCode, vars Variables, md Metadata) (Metadata, error) {
+	md.skipped = 0
+
 	if qc == nil {
-		return Metadata{}, fmt.Errorf("qcode is nil")
+		return md, fmt.Errorf("qcode is nil")
 	}
 
 	switch qc.Type {
 	case qcode.QTQuery:
-		return co.compileQuery(w, qc, vars)
+		return co.compileQueryWithMetadata(w, qc, vars, md)
 
 	case qcode.QTInsert,
 		qcode.QTUpdate,
 		qcode.QTDelete,
 		qcode.QTUpsert:
 		return co.compileMutation(w, qc, vars)
+
+	default:
+		return Metadata{}, fmt.Errorf("Unknown operation type %d", qc.Type)
 	}
 
-	return Metadata{}, fmt.Errorf("Unknown operation type %d", qc.Type)
-}
-
-func (co *Compiler) compileQuery(w io.Writer, qc *qcode.QCode, vars Variables) (Metadata, error) {
-	return co.compileQueryWithMetadata(w, qc, vars, Metadata{})
 }
 
 func (co *Compiler) compileQueryWithMetadata(
@@ -176,7 +180,7 @@ func (co *Compiler) compileQueryWithMetadata(
 			}
 
 			for _, cid := range sel.Children {
-				if hasBit(c.md.Skipped, uint32(cid)) {
+				if hasBit(c.md.skipped, uint32(cid)) {
 					continue
 				}
 				child := &c.s[cid]
@@ -354,7 +358,7 @@ func (c *compilerContext) initSelect(sel *qcode.Select, ti *DBTableInfo, vars Va
 			if _, ok := colmap[rel.Left.Col]; !ok {
 				cols = append(cols, &qcode.Column{Table: ti.Name, Name: rel.Left.Col, FieldName: rel.Right.Col})
 				colmap[rel.Left.Col] = struct{}{}
-				c.md.Skipped |= (1 << uint(id))
+				c.md.skipped |= (1 << uint(id))
 			}
 
 		default:
@@ -622,7 +626,7 @@ func (c *compilerContext) renderJoinColumns(sel *qcode.Select, ti *DBTableInfo,
 	i := colsRendered
 
 	for _, id := range sel.Children {
-		if hasBit(c.md.Skipped, uint32(id)) {
+		if hasBit(c.md.skipped, uint32(id)) {
 			continue
 		}
 		childSel := &c.s[id]
@@ -804,7 +808,7 @@ func (c *compilerContext) renderCursorCTE(sel *qcode.Select) error {
 		quoted(c.w, ob.Col)
 	}
 	io.WriteString(c.w, ` FROM string_to_array(`)
-	c.renderValueExp(Param{Name: "cursor", Type: "json"})
+	c.md.renderValueExp(c.w, Param{Name: "cursor", Type: "json"})
 	io.WriteString(c.w, `, ',') as a) `)
 	return nil
 }
@@ -1102,7 +1106,7 @@ func (c *compilerContext) renderOp(ex *qcode.Exp, ti *DBTableInfo) error {
 		} else {
 			io.WriteString(c.w, `) @@ to_tsquery(`)
 		}
-		c.renderValueExp(Param{Name: ex.Val, Type: "string"})
+		c.md.renderValueExp(c.w, Param{Name: ex.Val, Type: "string"})
 		io.WriteString(c.w, `))`)
 
 		return nil
@@ -1191,7 +1195,7 @@ func (c *compilerContext) renderVal(ex *qcode.Exp, vars map[string]string, col *
 		switch {
 		case ok && strings.HasPrefix(val, "sql:"):
 			io.WriteString(c.w, `(`)
-			c.renderVar(val[4:], c.renderValueExp)
+			c.md.RenderVar(c.w, val[4:])
 			io.WriteString(c.w, `)`)
 
 		case ok:
@@ -1199,7 +1203,7 @@ func (c *compilerContext) renderVal(ex *qcode.Exp, vars map[string]string, col *
 
 		case ex.Op == qcode.OpIn || ex.Op == qcode.OpNotIn:
 			io.WriteString(c.w, `(ARRAY(SELECT json_array_elements_text(`)
-			c.renderValueExp(Param{Name: ex.Val, Type: col.Type, IsArray: true})
+			c.md.renderValueExp(c.w, Param{Name: ex.Val, Type: col.Type, IsArray: true})
 			io.WriteString(c.w, `))`)
 
 			io.WriteString(c.w, ` :: `)
@@ -1208,7 +1212,7 @@ func (c *compilerContext) renderVal(ex *qcode.Exp, vars map[string]string, col *
 			return
 
 		default:
-			c.renderValueExp(Param{Name: ex.Val, Type: col.Type, IsArray: false})
+			c.md.renderValueExp(c.w, Param{Name: ex.Val, Type: col.Type, IsArray: false})
 		}
 
 	case qcode.ValRef:
@@ -1222,54 +1226,6 @@ func (c *compilerContext) renderVal(ex *qcode.Exp, vars map[string]string, col *
 	io.WriteString(c.w, col.Type)
 }
 
-func (c *compilerContext) renderValueExp(p Param) {
-	io.WriteString(c.w, `$`)
-	if v, ok := c.md.pindex[p.Name]; ok {
-		int32String(c.w, int32(v))
-
-	} else {
-		c.md.Params = append(c.md.Params, p)
-		n := len(c.md.Params)
-
-		if c.md.pindex == nil {
-			c.md.pindex = make(map[string]int)
-		}
-		c.md.pindex[p.Name] = n
-		int32String(c.w, int32(n))
-	}
-}
-
-func (c *compilerContext) renderVar(vv string, fn func(Param)) {
-	f, s := -1, 0
-
-	for i := range vv {
-		v := vv[i]
-		switch {
-		case (i > 0 && vv[i-1] != '\\' && v == '$') || v == '$':
-			if (i - s) > 0 {
-				io.WriteString(c.w, vv[s:i])
-			}
-			f = i
-
-		case (v < 'a' && v > 'z') &&
-			(v < 'A' && v > 'Z') &&
-			(v < '0' && v > '9') &&
-			v != '_' &&
-			f != -1 &&
-			(i-f) > 1:
-			fn(Param{Name: vv[f+1 : i]})
-			s = i
-			f = -1
-		}
-	}
-
-	if f != -1 && (len(vv)-f) > 1 {
-		fn(Param{Name: vv[f+1:]})
-	} else {
-		io.WriteString(c.w, vv[s:])
-	}
-}
-
 func funcPrefixLen(fm map[string]*DBFunction, fn string) int {
 	switch {
 	case strings.HasPrefix(fn, "avg_"):
diff --git a/core/internal/psql/update.go b/core/internal/psql/update.go
index 21395d9..cbdaf98 100644
--- a/core/internal/psql/update.go
+++ b/core/internal/psql/update.go
@@ -22,7 +22,7 @@ func (c *compilerContext) renderUpdate(
 	}
 
 	io.WriteString(c.w, `WITH "_sg_input" AS (SELECT `)
-	c.renderValueExp(Param{Name: qc.ActionVar, Type: "json"})
+	c.md.renderValueExp(c.w, Param{Name: qc.ActionVar, Type: "json"})
 	// io.WriteString(c.w, qc.ActionVar)
 	io.WriteString(c.w, ` :: json AS j)`)
 
diff --git a/core/internal/qcode/parse_test.go b/core/internal/qcode/parse_test.go
index c146dc7..c465e95 100644
--- a/core/internal/qcode/parse_test.go
+++ b/core/internal/qcode/parse_test.go
@@ -2,8 +2,9 @@ package qcode
 
 import (
 	"errors"
-	"github.com/chirino/graphql/schema"
 	"testing"
+
+	"github.com/chirino/graphql/schema"
 )
 
 func TestCompile1(t *testing.T) {
@@ -130,6 +131,22 @@ updateThread {
 
 }
 
+func TestFragmentsCompile(t *testing.T) {
+	gql := `
+fragment userFields on user {
+  name
+  email
+}
+	
+query { users { ...userFields } }`
+	qcompile, _ := NewCompiler(Config{})
+	_, err := qcompile.Compile([]byte(gql), "anon")
+
+	if err == nil {
+		t.Fatal(errors.New("expecting an error"))
+	}
+}
+
 var gql = []byte(`
 	{products(
 		# returns only 30 items
diff --git a/core/prepare.go b/core/prepare.go
index 2f6f235..a2f57ac 100644
--- a/core/prepare.go
+++ b/core/prepare.go
@@ -125,7 +125,7 @@ func (sg *SuperGraph) prepareRoleStmt() error {
 	}
 
 	io.WriteString(w, ` ELSE $2 END) FROM (`)
-	io.WriteString(w, sg.conf.RolesQuery)
+	io.WriteString(w, rq)
 	io.WriteString(w, `) AS "_sg_auth_roles_query" LIMIT 1) `)
 	io.WriteString(w, `ELSE 'anon' END) FROM (VALUES (1)) AS "_sg_auth_filler" LIMIT 1; `)
 
diff --git a/core/remote.go b/core/remote.go
index e905520..5515772 100644
--- a/core/remote.go
+++ b/core/remote.go
@@ -22,7 +22,7 @@ func (sg *SuperGraph) execRemoteJoin(st *stmt, data []byte, hdr http.Header) ([]
 	// fetch the field name used within the db response json
 	// that are used to mark insertion points and the mapping between
 	// those field names and their select objects
-	fids, sfmap := sg.parentFieldIds(&h, sel, st.md.Skipped)
+	fids, sfmap := sg.parentFieldIds(&h, sel, st.md.Skipped())
 
 	// fetch the field values of the marked insertion points
 	// these values contain the id to be used with fetching remote data
@@ -67,7 +67,7 @@ func (sg *SuperGraph) resolveRemote(
 	to := toA[:1]
 
 	// use the json key to find the related Select object
-	h.Write(field.Key)
+	_, _ = h.Write(field.Key)
 	k1 := h.Sum64()
 
 	s, ok := sfmap[k1]
@@ -136,7 +136,7 @@ func (sg *SuperGraph) resolveRemotes(
 	for i, id := range from {
 
 		// use the json key to find the related Select object
-		h.Write(id.Key)
+		_, _ = h.Write(id.Key)
 		k1 := h.Sum64()
 
 		s, ok := sfmap[k1]
@@ -230,7 +230,7 @@ func (sg *SuperGraph) parentFieldIds(h *maphash.Hash, sel []qcode.Select, skippe
 			fm[n] = r.IDField
 			n++
 
-			h.Write(r.IDField)
+			_, _ = h.Write(r.IDField)
 			sm[h.Sum64()] = s
 		}
 	}
diff --git a/core/resolve.go b/core/resolve.go
index bdb4857..0f4e804 100644
--- a/core/resolve.go
+++ b/core/resolve.go
@@ -86,7 +86,7 @@ func (sg *SuperGraph) initRemotes(t Table) error {
 		sg.rmap[mkkey(&h, r.Name, t.Name)] = rf
 
 		// index resolver obj by IDField
-		h.Write(rf.IDField)
+		_, _ = h.Write(rf.IDField)
 		sg.rmap[h.Sum64()] = rf
 	}
 
diff --git a/jsn/filter.go b/jsn/filter.go
index 6b9c6dd..60ddc12 100644
--- a/jsn/filter.go
+++ b/jsn/filter.go
@@ -12,7 +12,7 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 	h := maphash.Hash{}
 
 	for i := range keys {
-		h.WriteString(keys[i])
+		_, _ = h.WriteString(keys[i])
 		kmap[h.Sum64()] = struct{}{}
 		h.Reset()
 	}
@@ -134,7 +134,7 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 			cb := b[s:(e + 1)]
 			e = 0
 
-			h.Write(k)
+			_, _ = h.Write(k)
 			_, ok := kmap[h.Sum64()]
 			h.Reset()
 
diff --git a/jsn/get.go b/jsn/get.go
index 52f00ed..a9b3381 100644
--- a/jsn/get.go
+++ b/jsn/get.go
@@ -44,7 +44,7 @@ func Get(b []byte, keys [][]byte) []Field {
 	h := maphash.Hash{}
 
 	for i := range keys {
-		h.Write(keys[i])
+		_, _ = h.Write(keys[i])
 		kmap[h.Sum64()] = struct{}{}
 		h.Reset()
 	}
@@ -144,7 +144,7 @@ func Get(b []byte, keys [][]byte) []Field {
 		}
 
 		if e != 0 {
-			h.Write(k)
+			_, _ = h.Write(k)
 			_, ok := kmap[h.Sum64()]
 			h.Reset()