super-graph/core/internal/psql/query.go

//nolint:errcheck
package psql

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"strings"

	"github.com/dosco/super-graph/core/internal/qcode"
	"github.com/dosco/super-graph/core/internal/util"
)

const (
	closeBlock = 500
)

type Variables map[string]json.RawMessage

type Config struct {
	Schema *DBSchema
	Vars   map[string]string
}

type Compiler struct {
	schema *DBSchema
	vars   map[string]string
}

func NewCompiler(conf Config) *Compiler {
	return &Compiler{
		schema: conf.Schema,
		vars:   conf.Vars,
	}
}

func (c *Compiler) AddRelationship(child, parent string, rel *DBRel) error {
	return c.schema.SetRel(child, parent, rel)
}

func (c *Compiler) IDColumn(table string) (*DBColumn, error) {
	ti, err := c.schema.GetTable(table)
	if err != nil {
		return nil, err
	}

	if ti.PrimaryCol == nil {
		return nil, fmt.Errorf("no primary key column found")
	}

	return ti.PrimaryCol, nil
}

type compilerContext struct {
	w io.Writer
	s []qcode.Select
	*Compiler
}

func (co *Compiler) CompileEx(qc *qcode.QCode, vars Variables) (uint32, []byte, error) {
	w := &bytes.Buffer{}
	skipped, err := co.Compile(qc, w, vars)
	return skipped, w.Bytes(), err
}

func (co *Compiler) Compile(qc *qcode.QCode, w io.Writer, vars Variables) (uint32, error) {
	switch qc.Type {
	case qcode.QTQuery:
		return co.compileQuery(qc, w, vars)
	case qcode.QTInsert, qcode.QTUpdate, qcode.QTDelete, qcode.QTUpsert:
		return co.compileMutation(qc, w, vars)
	}

	return 0, fmt.Errorf("Unknown operation type %d", qc.Type)
}

func (co *Compiler) compileQuery(qc *qcode.QCode, w io.Writer, vars Variables) (uint32, error) {
	if len(qc.Selects) == 0 {
		return 0, errors.New("empty query")
	}

	c := &compilerContext{w, qc.Selects, co}

	st := NewIntStack()
	i := 0

	io.WriteString(c.w, `SELECT jsonb_build_object(`)
	for _, id := range qc.Roots {
		if i != 0 {
			io.WriteString(c.w, `, `)
		}

		root := &qc.Selects[id]

		if root.SkipRender || len(root.Cols) == 0 {
			squoted(c.w, root.FieldName)
			io.WriteString(c.w, `, `)
			io.WriteString(c.w, `NULL`)

		} else {
			st.Push(root.ID + closeBlock)
			st.Push(root.ID)
			c.renderRootSelect(root)
		}

		i++
	}

	var ignored uint32

	if st.Len() != 0 {
		io.WriteString(c.w, `) as "__root" FROM `)
	} else {
		io.WriteString(c.w, `) as "__root"`)
		return ignored, nil
	}

	for {
		if st.Len() == 0 {
			break
		}

		id := st.Pop()

		if id < closeBlock {
			sel := &c.s[id]

			if len(sel.Cols) == 0 {
				continue
			}

			ti, err := c.schema.GetTable(sel.Name)
			if err != nil {
				return 0, err
			}

			if sel.ParentID == -1 {
				io.WriteString(c.w, `(`)
			} else {
				c.renderLateralJoin(sel)
			}

			if !ti.IsSingular {
				c.renderPluralSelect(sel, ti)
			}

			skipped, err := c.renderSelect(sel, ti, vars)
			if err != nil {
				return 0, err
			}
			ignored |= skipped

			for _, cid := range sel.Children {
				if hasBit(skipped, uint32(cid)) {
					continue
				}
				child := &c.s[cid]
				if child.SkipRender {
					continue
				}

				st.Push(child.ID + closeBlock)
				st.Push(child.ID)
			}

		} else {
			sel := &c.s[(id - closeBlock)]

			ti, err := c.schema.GetTable(sel.Name)
			if err != nil {
				return 0, err
			}

			io.WriteString(c.w, `)`)
			aliasWithID(c.w, "__sr", sel.ID)

			io.WriteString(c.w, `)`)
			aliasWithID(c.w, "__sj", sel.ID)

			if !ti.IsSingular {
				io.WriteString(c.w, `)`)
				aliasWithID(c.w, "__sj", sel.ID)
			}

			if sel.ParentID == -1 {
				if st.Len() != 0 {
					io.WriteString(c.w, `, `)
				}
			} else {
				c.renderLateralJoinClose(sel)
			}

			if len(sel.Args) != 0 {
				i := 0
				for _, v := range sel.Args {
					qcode.FreeNode(v, 500)
					i++
				}
			}
		}
	}

	return ignored, nil
}

func (c *compilerContext) renderPluralSelect(sel *qcode.Select, ti *DBTableInfo) error {
	io.WriteString(c.w, `SELECT coalesce(jsonb_agg("__sj_`)
	int2string(c.w, sel.ID)
	io.WriteString(c.w, `"."json"), '[]') as "json"`)

	if sel.Paging.Type != qcode.PtOffset {
		n := 0

		// check if primary key already included in order by
		// query argument
		for _, ob := range sel.OrderBy {
			if ob.Col == ti.PrimaryCol.Key {
				n = 1
				break
			}
		}

		if n == 1 {
			n = len(sel.OrderBy)
		} else {
			n = len(sel.OrderBy) + 1
		}

		io.WriteString(c.w, `, CONCAT_WS(','`)
		for i := 0; i < n; i++ {
			io.WriteString(c.w, `, max("__cur_`)
			int2string(c.w, int32(i))
			io.WriteString(c.w, `")`)
		}
		io.WriteString(c.w, `) as "cursor"`)
	}

	io.WriteString(c.w, ` FROM (`)
	return nil
}

func (c *compilerContext) renderRootSelect(sel *qcode.Select) error {
	io.WriteString(c.w, `'`)
	io.WriteString(c.w, sel.FieldName)
	io.WriteString(c.w, `', `)

	io.WriteString(c.w, `"__sj_`)
	int2string(c.w, sel.ID)
	io.WriteString(c.w, `"."json"`)

	if sel.Paging.Type != qcode.PtOffset {
		io.WriteString(c.w, `, '`)
		io.WriteString(c.w, sel.FieldName)
		io.WriteString(c.w, `_cursor', `)

		io.WriteString(c.w, `"__sj_`)
		int2string(c.w, sel.ID)
		io.WriteString(c.w, `"."cursor"`)
	}

	return nil
}

func (c *compilerContext) initSelect(sel *qcode.Select, ti *DBTableInfo, vars Variables) (uint32, []*qcode.Column, error) {
	var skipped uint32

	cols := make([]*qcode.Column, 0, len(sel.Cols))
	colmap := make(map[string]struct{}, len(sel.Cols))

	for i := range sel.Cols {
		colmap[sel.Cols[i].Name] = struct{}{}
	}

	for i := range sel.OrderBy {
		colmap[sel.OrderBy[i].Col] = struct{}{}
	}

	if sel.Paging.Type != qcode.PtOffset {
		colmap[ti.PrimaryCol.Key] = struct{}{}
		addPrimaryKey := true

		for _, ob := range sel.OrderBy {
			if ob.Col == ti.PrimaryCol.Key {
				addPrimaryKey = false
				break
			}
		}

		if addPrimaryKey {
			ob := &qcode.OrderBy{Col: ti.PrimaryCol.Name, Order: qcode.OrderAsc}

			if sel.Paging.Type == qcode.PtBackward {
				ob.Order = qcode.OrderDesc
			}
			sel.OrderBy = append(sel.OrderBy, ob)
		}
	}

	if sel.Paging.Cursor {
		c.addSeekPredicate(sel)
	}

	for _, id := range sel.Children {
		child := &c.s[id]

		rel, err := c.schema.GetRel(child.Name, ti.Name)
		if err != nil {
			return 0, nil, err
			//skipped |= (1 << uint(id))
			//continue
		}

		switch rel.Type {
		case RelOneToOne, RelOneToMany:
			if _, ok := colmap[rel.Right.Col]; !ok {
				cols = append(cols, &qcode.Column{Table: ti.Name, Name: rel.Right.Col, FieldName: rel.Right.Col})
				colmap[rel.Right.Col] = struct{}{}
			}

		case RelOneToManyThrough:
			if _, ok := colmap[rel.Left.Col]; !ok {
				cols = append(cols, &qcode.Column{Table: ti.Name, Name: rel.Left.Col, FieldName: rel.Left.Col})
				colmap[rel.Left.Col] = struct{}{}
			}

		case RelEmbedded:
			if _, ok := colmap[rel.Left.Col]; !ok {
				cols = append(cols, &qcode.Column{Table: ti.Name, Name: rel.Left.Col, FieldName: rel.Left.Col})
				colmap[rel.Left.Col] = struct{}{}
			}

		case RelRemote:
			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{}{}
				skipped |= (1 << uint(id))
			}

		default:
			return 0, nil, fmt.Errorf("unknown relationship %s", rel)
			//skipped |= (1 << uint(id))
		}
	}

	return skipped, cols, nil
}

// This
// (A, B, C) >= (X, Y, Z)
//
// Becomes
// (A > X)
//   OR ((A = X) AND (B > Y))
//   OR ((A = X) AND (B = Y) AND (C > Z))
//   OR ((A = X) AND (B = Y) AND (C = Z))

func (c *compilerContext) addSeekPredicate(sel *qcode.Select) error {
	var or, and *qcode.Exp

	obLen := len(sel.OrderBy)

	if obLen > 1 {
		or = qcode.NewFilter()
		or.Op = qcode.OpOr
	}

	for i := 0; i < obLen; i++ {
		if i > 0 {
			and = qcode.NewFilter()
			and.Op = qcode.OpAnd
		}

		for n, ob := range sel.OrderBy {
			f := qcode.NewFilter()
			f.Col = ob.Col
			f.Type = qcode.ValRef
			f.Table = "__cur"
			f.Val = ob.Col

			if obLen == 1 {
				qcode.AddFilter(sel, f)
				return nil
			}

			switch {
			case i > 0 && n != i:
				f.Op = qcode.OpEquals
			case ob.Order == qcode.OrderDesc:
				f.Op = qcode.OpLesserThan
			default:
				f.Op = qcode.OpGreaterThan
			}

			if and != nil {
				and.Children = append(and.Children, f)
			} else {
				or.Children = append(or.Children, f)
			}

			if n == i {
				break
			}
		}

		if and != nil {
			or.Children = append(or.Children, and)
		}
	}

	qcode.AddFilter(sel, or)
	return nil
}

func (c *compilerContext) renderSelect(sel *qcode.Select, ti *DBTableInfo, vars Variables) (uint32, error) {
	var rel *DBRel
	var err error

	if sel.ParentID != -1 {
		parent := c.s[sel.ParentID]

		rel, err = c.schema.GetRel(ti.Name, parent.Name)
		if err != nil {
			return 0, err
		}
	}

	skipped, childCols, err := c.initSelect(sel, ti, vars)
	if err != nil {
		return 0, err
	}

	// SELECT
	// io.WriteString(c.w, `SELECT jsonb_build_object(`)
	// if err := c.renderColumns(sel, ti, skipped); err != nil {
	// 	return 0, err
	// }

	io.WriteString(c.w, `SELECT to_jsonb("__sr_`)
	int2string(c.w, sel.ID)
	io.WriteString(c.w, `".*) `)

	if sel.Paging.Type != qcode.PtOffset {
		for i := range sel.OrderBy {
			io.WriteString(c.w, `- '__cur_`)
			int2string(c.w, int32(i))
			io.WriteString(c.w, `' `)
		}
	}

	io.WriteString(c.w, `AS "json"`)

	if sel.Paging.Type != qcode.PtOffset {
		for i := range sel.OrderBy {
			io.WriteString(c.w, `, "__cur_`)
			int2string(c.w, int32(i))
			io.WriteString(c.w, `"`)
		}
	}

	io.WriteString(c.w, `FROM (SELECT `)

	if err := c.renderColumns(sel, ti, skipped); err != nil {
		return 0, err
	}

	if sel.Paging.Type != qcode.PtOffset {
		for i, ob := range sel.OrderBy {
			io.WriteString(c.w, `, LAST_VALUE(`)
			colWithTableID(c.w, ti.Name, sel.ID, ob.Col)
			io.WriteString(c.w, `) OVER() AS "__cur_`)
			int2string(c.w, int32(i))
			io.WriteString(c.w, `"`)
		}
	}

	io.WriteString(c.w, ` FROM (`)

	// FROM (SELECT .... )
	err = c.renderBaseSelect(sel, ti, rel, childCols, skipped)
	if err != nil {
		return skipped, err
	}

	//fmt.Fprintf(w, `) AS "%s_%d"`, c.sel.Name, c.sel.ID)
	io.WriteString(c.w, `)`)
	aliasWithID(c.w, ti.Name, sel.ID)

	// END-FROM

	return skipped, nil
}

func (c *compilerContext) renderLateralJoin(sel *qcode.Select) error {
	io.WriteString(c.w, ` LEFT OUTER JOIN LATERAL (`)
	return nil
}

func (c *compilerContext) renderLateralJoinClose(sel *qcode.Select) error {
	// io.WriteString(c.w, `) `)
	// aliasWithID(c.w, "__sj", sel.ID)
	io.WriteString(c.w, ` ON ('true')`)
	return nil
}

func (c *compilerContext) renderJoin(sel *qcode.Select, ti *DBTableInfo) error {
	parent := &c.s[sel.ParentID]
	return c.renderJoinByName(ti.Name, parent.Name, parent.ID)
}

func (c *compilerContext) renderJoinByName(table, parent string, id int32) error {
	rel, err := c.schema.GetRel(table, parent)
	if err != nil {
		return err
	}

	// This join is only required for one-to-many relations since
	// these make use of join tables that need to be pulled in.
	if rel.Type != RelOneToManyThrough {
		return err
	}

	pt, err := c.schema.GetTable(parent)
	if err != nil {
		return err
	}

	//fmt.Fprintf(w, ` LEFT OUTER JOIN "%s" ON (("%s"."%s") = ("%s_%d"."%s"))`,
	//rel.Through, rel.Through, rel.ColT, c.parent.Name, c.parent.ID, rel.Left.Col)
	io.WriteString(c.w, ` LEFT OUTER JOIN "`)
	io.WriteString(c.w, rel.Through)
	io.WriteString(c.w, `" ON ((`)
	colWithTable(c.w, rel.Through, rel.ColT)
	io.WriteString(c.w, `) = (`)
	colWithTableID(c.w, pt.Name, id, rel.Left.Col)
	io.WriteString(c.w, `))`)

	return nil
}

func (c *compilerContext) renderColumns(sel *qcode.Select, ti *DBTableInfo, skipped uint32) error {
	i := 0
	var cn string

	for _, col := range sel.Cols {
		if n := funcPrefixLen(c.schema.fm, col.Name); n != 0 {
			if !sel.Functions {
				continue
			}
			cn = col.Name[n:]
		} else {
			cn = col.Name

			if strings.HasSuffix(cn, "_cursor") {
				continue
			}
		}

		if len(sel.Allowed) != 0 {
			if _, ok := sel.Allowed[cn]; !ok {
				continue
			}
		}

		if i != 0 {
			io.WriteString(c.w, ", ")
		}

		colWithTableID(c.w, ti.Name, sel.ID, col.Name)
		alias(c.w, col.FieldName)

		i++
	}

	i += c.renderRemoteRelColumns(sel, ti, i)

	return c.renderJoinColumns(sel, ti, skipped, i)
}

func (c *compilerContext) renderRemoteRelColumns(sel *qcode.Select, ti *DBTableInfo, colsRendered int) int {
	i := colsRendered

	for _, id := range sel.Children {
		child := &c.s[id]

		rel, err := c.schema.GetRel(child.Name, sel.Name)
		if err != nil || rel.Type != RelRemote {
			continue
		}
		if i != 0 || len(sel.Cols) != 0 {
			io.WriteString(c.w, ", ")
		}

		colWithTableID(c.w, ti.Name, sel.ID, rel.Left.Col)
		alias(c.w, rel.Right.Col)
		i++
	}

	return i
}

func (c *compilerContext) renderJoinColumns(sel *qcode.Select, ti *DBTableInfo, skipped uint32, colsRendered int) error {
	// columns previously rendered
	i := colsRendered

	for _, id := range sel.Children {
		if hasBit(skipped, uint32(id)) {
			continue
		}
		childSel := &c.s[id]

		if i != 0 {
			io.WriteString(c.w, ", ")
		}

		if childSel.SkipRender {
			io.WriteString(c.w, `NULL`)
			alias(c.w, childSel.FieldName)
			continue
		}

		io.WriteString(c.w, `"__sj_`)
		int2string(c.w, childSel.ID)
		io.WriteString(c.w, `"."json"`)
		alias(c.w, childSel.FieldName)

		if childSel.Paging.Type != qcode.PtOffset {
			io.WriteString(c.w, `, "__sj_`)
			int2string(c.w, childSel.ID)
			io.WriteString(c.w, `"."cursor" AS "`)
			io.WriteString(c.w, childSel.FieldName)
			io.WriteString(c.w, `_cursor"`)
		}

		i++
	}

	return nil
}

func (c *compilerContext) renderBaseSelect(sel *qcode.Select, ti *DBTableInfo, rel *DBRel,
	childCols []*qcode.Column, skipped uint32) error {
	isRoot := (rel == nil)
	isFil := (sel.Where != nil && sel.Where.Op != qcode.OpNop)
	hasOrder := len(sel.OrderBy) != 0

	if sel.Paging.Cursor {
		c.renderCursorCTE(sel)
	}

	io.WriteString(c.w, `SELECT `)

	if len(sel.DistinctOn) != 0 {
		c.renderDistinctOn(sel, ti)
	}

	realColsRendered, isAgg, err := c.renderBaseColumns(sel, ti, childCols, skipped)
	if err != nil {
		return err
	}

	io.WriteString(c.w, ` FROM `)

	c.renderFrom(sel, ti, rel)

	if isRoot && isFil {
		io.WriteString(c.w, ` WHERE (`)
		if err := c.renderWhere(sel, ti); err != nil {
			return err
		}
		io.WriteString(c.w, `)`)
	}

	if !isRoot {
		if err := c.renderJoin(sel, ti); err != nil {
			return err
		}

		io.WriteString(c.w, ` WHERE (`)
		if err := c.renderRelationship(sel, ti); err != nil {
			return err
		}
		if isFil {
			io.WriteString(c.w, ` AND `)
			if err := c.renderWhere(sel, ti); err != nil {
				return err
			}
		}
		io.WriteString(c.w, `)`)
	}

	if isAgg && len(realColsRendered) != 0 {
		io.WriteString(c.w, ` GROUP BY `)

		for i, id := range realColsRendered {
			c.renderComma(i)
			//fmt.Fprintf(w, `"%s"."%s"`, c.sel.Name, c.sel.Cols[id].Name)
			colWithTable(c.w, ti.Name, sel.Cols[id].Name)
		}
	}

	if hasOrder {
		if err := c.renderOrderBy(sel, ti); err != nil {
			return err
		}
	}

	switch {
	case ti.IsSingular:
		io.WriteString(c.w, ` LIMIT ('1') :: integer`)

	case len(sel.Paging.Limit) != 0:
		//fmt.Fprintf(w, ` LIMIT ('%s') :: integer`, c.sel.Paging.Limit)
		io.WriteString(c.w, ` LIMIT ('`)
		io.WriteString(c.w, sel.Paging.Limit)
		io.WriteString(c.w, `') :: integer`)

	case sel.Paging.NoLimit:
		break

	default:
		io.WriteString(c.w, ` LIMIT ('20') :: integer`)
	}

	if len(sel.Paging.Offset) != 0 {
		//fmt.Fprintf(w, ` OFFSET ('%s') :: integer`, c.sel.Paging.Offset)
		io.WriteString(c.w, ` OFFSET ('`)
		io.WriteString(c.w, sel.Paging.Offset)
		io.WriteString(c.w, `') :: integer`)
	}

	return nil
}

func (c *compilerContext) renderFrom(sel *qcode.Select, ti *DBTableInfo, rel *DBRel) error {
	if rel != nil && rel.Type == RelEmbedded {
		// jsonb_to_recordset('[{"a":1,"b":[1,2,3],"c":"bar"}, {"a":2,"b":[1,2,3],"c":"bar"}]') as x(a int, b text, d text);

		io.WriteString(c.w, `"`)
		io.WriteString(c.w, rel.Left.Table)
		io.WriteString(c.w, `", `)

		io.WriteString(c.w, ti.Type)
		io.WriteString(c.w, `_to_recordset(`)
		colWithTable(c.w, rel.Left.Table, rel.Right.Col)
		io.WriteString(c.w, `) AS `)

		io.WriteString(c.w, `"`)
		io.WriteString(c.w, ti.Name)
		io.WriteString(c.w, `"`)

		io.WriteString(c.w, `(`)
		for i, col := range ti.Columns {
			if i != 0 {
				io.WriteString(c.w, `, `)
			}
			io.WriteString(c.w, col.Name)
			io.WriteString(c.w, ` `)
			io.WriteString(c.w, col.Type)
		}
		io.WriteString(c.w, `)`)

	} else {
		//fmt.Fprintf(w, ` FROM "%s"`, c.sel.Name)
		io.WriteString(c.w, `"`)
		io.WriteString(c.w, ti.Name)
		io.WriteString(c.w, `"`)
	}

	if sel.Paging.Cursor {
		io.WriteString(c.w, `, "__cur"`)
	}

	return nil
}

func (c *compilerContext) renderCursorCTE(sel *qcode.Select) error {
	io.WriteString(c.w, `WITH "__cur" AS (SELECT `)
	for i, ob := range sel.OrderBy {
		if i != 0 {
			io.WriteString(c.w, `, `)
		}
		io.WriteString(c.w, `a[`)
		int2string(c.w, int32(i+1))
		io.WriteString(c.w, `] as `)
		quoted(c.w, ob.Col)
	}
	io.WriteString(c.w, ` FROM string_to_array('{{cursor}}', ',') as a) `)
	return nil
}

func (c *compilerContext) renderRelationship(sel *qcode.Select, ti *DBTableInfo) error {
	parent := c.s[sel.ParentID]

	pti, err := c.schema.GetTable(parent.Name)
	if err != nil {
		return err
	}

	return c.renderRelationshipByName(ti.Name, pti.Name, parent.ID)
}

func (c *compilerContext) renderRelationshipByName(table, parent string, id int32) error {
	rel, err := c.schema.GetRel(table, parent)
	if err != nil {
		return err
	}

	io.WriteString(c.w, `((`)

	switch rel.Type {
	case RelOneToOne, RelOneToMany:

		//fmt.Fprintf(w, `(("%s"."%s") = ("%s_%d"."%s"))`,
		//c.sel.Name, rel.Left.Col, c.parent.Name, c.parent.ID, rel.Right.Col)

		switch {
		case !rel.Left.Array && rel.Right.Array:
			colWithTable(c.w, table, rel.Left.Col)
			io.WriteString(c.w, `) = any (`)
			colWithTableID(c.w, parent, id, rel.Right.Col)

		case rel.Left.Array && !rel.Right.Array:
			colWithTableID(c.w, parent, id, rel.Right.Col)
			io.WriteString(c.w, `) = any (`)
			colWithTable(c.w, table, rel.Left.Col)

		default:
			colWithTable(c.w, table, rel.Left.Col)
			io.WriteString(c.w, `) = (`)
			colWithTableID(c.w, parent, id, rel.Right.Col)
		}

	case RelOneToManyThrough:
		// This requires the through table to be joined onto this select
		//fmt.Fprintf(w, `(("%s"."%s") = ("%s"."%s"))`,
		//c.sel.Name, rel.Left.Col, rel.Through, rel.Right.Col)

		switch {
		case !rel.Left.Array && rel.Right.Array:
			colWithTable(c.w, table, rel.Left.Col)
			io.WriteString(c.w, `) = any (`)
			colWithTable(c.w, rel.Through, rel.Right.Col)

		case rel.Left.Array && !rel.Right.Array:
			colWithTable(c.w, rel.Through, rel.Right.Col)
			io.WriteString(c.w, `) = any (`)
			colWithTable(c.w, table, rel.Left.Col)

		default:
			colWithTable(c.w, table, rel.Left.Col)
			io.WriteString(c.w, `) = (`)
			colWithTable(c.w, rel.Through, rel.Right.Col)
		}

	case RelEmbedded:
		colWithTable(c.w, rel.Left.Table, rel.Left.Col)
		io.WriteString(c.w, `) = (`)
		colWithTableID(c.w, parent, id, rel.Left.Col)
	}

	io.WriteString(c.w, `))`)

	return nil
}

func (c *compilerContext) renderWhere(sel *qcode.Select, ti *DBTableInfo) error {
	if sel.Where != nil {
		return c.renderExp(sel.Where, ti, false)
	}
	return nil
}

func (c *compilerContext) renderExp(ex *qcode.Exp, ti *DBTableInfo, skipNested bool) error {
	st := util.NewStack()
	st.Push(ex)

	for {
		if st.Len() == 0 {
			break
		}

		intf := st.Pop()

		switch val := intf.(type) {
		case int32:
			switch val {
			case '(':
				io.WriteString(c.w, `(`)
			case ')':
				io.WriteString(c.w, `)`)
			}

		case qcode.ExpOp:
			switch val {
			case qcode.OpAnd:
				io.WriteString(c.w, ` AND `)
			case qcode.OpOr:
				io.WriteString(c.w, ` OR `)
			case qcode.OpNot:
				io.WriteString(c.w, `NOT `)
			case qcode.OpFalse:
				io.WriteString(c.w, `false`)
			default:
				return fmt.Errorf("11: unexpected value %v (%t)", intf, intf)
			}

		case *qcode.Exp:
			switch val.Op {
			case qcode.OpFalse:
				st.Push(val.Op)

			case qcode.OpAnd, qcode.OpOr:
				st.Push(')')
				for i := len(val.Children) - 1; i >= 0; i-- {
					st.Push(val.Children[i])
					if i > 0 {
						st.Push(val.Op)
					}
				}
				st.Push('(')

			case qcode.OpNot:
				st.Push(val.Children[0])
				st.Push(qcode.OpNot)

			default:
				if !skipNested && len(val.NestedCols) != 0 {
					io.WriteString(c.w, `EXISTS `)

					if err := c.renderNestedWhere(val, ti); err != nil {
						return err
					}

				} else {
					//fmt.Fprintf(w, `(("%s"."%s") `, c.sel.Name, val.Col)
					if err := c.renderOp(val, ti); err != nil {
						return err
					}
				}
			}
			//qcode.FreeExp(val)

		default:
			return fmt.Errorf("12: unexpected value %v (%t)", intf, intf)
		}
	}

	return nil
}

func (c *compilerContext) renderNestedWhere(ex *qcode.Exp, ti *DBTableInfo) error {
	for i := 0; i < len(ex.NestedCols)-1; i++ {
		cti, err := c.schema.GetTable(ex.NestedCols[i])
		if err != nil {
			return err
		}

		if i != 0 {
			io.WriteString(c.w, ` AND `)
		}

		io.WriteString(c.w, `(SELECT 1 FROM `)
		io.WriteString(c.w, cti.Name)

		if err := c.renderJoinByName(cti.Name, ti.Name, -1); err != nil {
			return err
		}

		io.WriteString(c.w, ` WHERE `)

		if err := c.renderRelationshipByName(cti.Name, ti.Name, -1); err != nil {
			return err
		}

		io.WriteString(c.w, ` AND (`)

		if err := c.renderExp(ex, cti, true); err != nil {
			return err
		}

		io.WriteString(c.w, `)`)

	}

	for i := 0; i < len(ex.NestedCols)-1; i++ {
		io.WriteString(c.w, `)`)
	}

	return nil
}

func (c *compilerContext) renderOp(ex *qcode.Exp, ti *DBTableInfo) error {
	var col *DBColumn
	var ok bool

	if ex.Op == qcode.OpNop {
		return nil
	}

	if len(ex.Col) != 0 {
		if col, ok = ti.ColMap[ex.Col]; !ok {
			return fmt.Errorf("no column '%s' found ", ex.Col)
		}

		io.WriteString(c.w, `((`)
		colWithTable(c.w, ti.Name, ex.Col)
		io.WriteString(c.w, `) `)
	}

	switch ex.Op {
	case qcode.OpEquals:
		io.WriteString(c.w, `=`)
	case qcode.OpNotEquals:
		io.WriteString(c.w, `!=`)
	case qcode.OpNotDistinct:
		io.WriteString(c.w, `IS NOT DISTINCT FROM`)
	case qcode.OpDistinct:
		io.WriteString(c.w, `IS DISTINCT FROM`)
	case qcode.OpGreaterOrEquals:
		io.WriteString(c.w, `>=`)
	case qcode.OpLesserOrEquals:
		io.WriteString(c.w, `<=`)
	case qcode.OpGreaterThan:
		io.WriteString(c.w, `>`)
	case qcode.OpLesserThan:
		io.WriteString(c.w, `<`)
	case qcode.OpIn:
		io.WriteString(c.w, `IN`)
	case qcode.OpNotIn:
		io.WriteString(c.w, `NOT IN`)
	case qcode.OpLike:
		io.WriteString(c.w, `LIKE`)
	case qcode.OpNotLike:
		io.WriteString(c.w, `NOT LIKE`)
	case qcode.OpILike:
		io.WriteString(c.w, `ILIKE`)
	case qcode.OpNotILike:
		io.WriteString(c.w, `NOT ILIKE`)
	case qcode.OpSimilar:
		io.WriteString(c.w, `SIMILAR TO`)
	case qcode.OpNotSimilar:
		io.WriteString(c.w, `NOT SIMILAR TO`)
	case qcode.OpContains:
		io.WriteString(c.w, `@>`)
	case qcode.OpContainedIn:
		io.WriteString(c.w, `<@`)
	case qcode.OpHasKey:
		io.WriteString(c.w, `?`)
	case qcode.OpHasKeyAny:
		io.WriteString(c.w, `?|`)
	case qcode.OpHasKeyAll:
		io.WriteString(c.w, `?&`)
	case qcode.OpIsNull:
		if strings.EqualFold(ex.Val, "true") {
			io.WriteString(c.w, `IS NULL)`)
		} else {
			io.WriteString(c.w, `IS NOT NULL)`)
		}
		return nil

	case qcode.OpEqID:
		if ti.PrimaryCol == nil {
			return fmt.Errorf("no primary key column defined for %s", ti.Name)
		}
		col = ti.PrimaryCol
		//fmt.Fprintf(w, `(("%s") =`, c.ti.PrimaryCol)
		io.WriteString(c.w, `((`)
		colWithTable(c.w, ti.Name, ti.PrimaryCol.Name)
		//io.WriteString(c.w, ti.PrimaryCol)
		io.WriteString(c.w, `) =`)

	case qcode.OpTsQuery:
		if ti.PrimaryCol == nil {
			return fmt.Errorf("no tsv column defined for %s", ti.Name)
		}
		//fmt.Fprintf(w, `(("%s") @@ websearch_to_tsquery('%s'))`, c.ti.TSVCol, val.Val)
		io.WriteString(c.w, `((`)
		colWithTable(c.w, ti.Name, ti.TSVCol.Name)
		if c.schema.ver >= 110000 {
			io.WriteString(c.w, `) @@ websearch_to_tsquery('{{`)
		} else {
			io.WriteString(c.w, `) @@ to_tsquery('{{`)
		}
		io.WriteString(c.w, ex.Val)
		io.WriteString(c.w, `}}'))`)
		return nil

	default:
		return fmt.Errorf("[Where] unexpected op code %d", ex.Op)
	}

	switch {
	case ex.Type == qcode.ValList:
		c.renderList(ex)
	case col == nil:
		return errors.New("no column found for expression value")
	default:
		c.renderVal(ex, c.vars, col)
	}

	io.WriteString(c.w, `)`)
	return nil
}

func (c *compilerContext) renderOrderBy(sel *qcode.Select, ti *DBTableInfo) error {
	io.WriteString(c.w, ` ORDER BY `)
	for i := range sel.OrderBy {
		if i != 0 {
			io.WriteString(c.w, `, `)
		}
		ob := sel.OrderBy[i]
		colWithTable(c.w, ti.Name, ob.Col)

		switch ob.Order {
		case qcode.OrderAsc:
			io.WriteString(c.w, ` ASC`)
		case qcode.OrderDesc:
			io.WriteString(c.w, ` DESC`)
		case qcode.OrderAscNullsFirst:
			io.WriteString(c.w, ` ASC NULLS FIRST`)
		case qcode.OrderDescNullsFirst:
			io.WriteString(c.w, ` DESC NULLLS FIRST`)
		case qcode.OrderAscNullsLast:
			io.WriteString(c.w, ` ASC NULLS LAST`)
		case qcode.OrderDescNullsLast:
			io.WriteString(c.w, ` DESC NULLS LAST`)
		default:
			return fmt.Errorf("13: unexpected value %v", ob.Order)
		}
	}
	return nil
}

func (c *compilerContext) renderDistinctOn(sel *qcode.Select, ti *DBTableInfo) {
	io.WriteString(c.w, `DISTINCT ON (`)
	for i := range sel.DistinctOn {
		if i != 0 {
			io.WriteString(c.w, `, `)
		}
		colWithTable(c.w, ti.Name, sel.DistinctOn[i])
	}
	io.WriteString(c.w, `) `)
}

func (c *compilerContext) renderList(ex *qcode.Exp) {
	io.WriteString(c.w, ` (`)
	for i := range ex.ListVal {
		if i != 0 {
			io.WriteString(c.w, `, `)
		}
		switch ex.ListType {
		case qcode.ValBool, qcode.ValInt, qcode.ValFloat:
			io.WriteString(c.w, ex.ListVal[i])
		case qcode.ValStr:
			io.WriteString(c.w, `'`)
			io.WriteString(c.w, ex.ListVal[i])
			io.WriteString(c.w, `'`)
		}
	}
	io.WriteString(c.w, `)`)
}

func (c *compilerContext) renderVal(ex *qcode.Exp, vars map[string]string, col *DBColumn) {
	io.WriteString(c.w, ` `)

	switch ex.Type {
	case qcode.ValVar:
		val, ok := vars[ex.Val]
		switch {
		case ok && strings.HasPrefix(val, "sql:"):
			io.WriteString(c.w, ` (`)
			io.WriteString(c.w, val[4:])
			io.WriteString(c.w, `)`)
		case ok:
			squoted(c.w, val)
		default:
			io.WriteString(c.w, ` '{{`)
			io.WriteString(c.w, ex.Val)
			io.WriteString(c.w, `}}'`)
		}

	case qcode.ValRef:
		colWithTable(c.w, ex.Table, ex.Col)

	default:
		squoted(c.w, ex.Val)
	}

	io.WriteString(c.w, ` :: `)
	io.WriteString(c.w, col.Type)
}

func funcPrefixLen(fm map[string]*DBFunction, fn string) int {
	switch {
	case strings.HasPrefix(fn, "avg_"):
		return 4
	case strings.HasPrefix(fn, "count_"):
		return 6
	case strings.HasPrefix(fn, "max_"):
		return 4
	case strings.HasPrefix(fn, "min_"):
		return 4
	case strings.HasPrefix(fn, "sum_"):
		return 4
	case strings.HasPrefix(fn, "stddev_"):
		return 7
	case strings.HasPrefix(fn, "stddev_pop_"):
		return 11
	case strings.HasPrefix(fn, "stddev_samp_"):
		return 12
	case strings.HasPrefix(fn, "variance_"):
		return 9
	case strings.HasPrefix(fn, "var_pop_"):
		return 8
	case strings.HasPrefix(fn, "var_samp_"):
		return 9
	}
	fnLen := len(fn)

	for k := range fm {
		kLen := len(k)
		if kLen < fnLen && k[0] == fn[0] && strings.HasPrefix(fn, k) && fn[kLen] == '_' {
			return kLen + 1
		}
	}
	return 0
}

func hasBit(n uint32, pos uint32) bool {
	val := n & (1 << pos)
	return (val > 0)
}

func alias(w io.Writer, alias string) {
	io.WriteString(w, ` AS "`)
	io.WriteString(w, alias)
	io.WriteString(w, `"`)
}

func aliasWithID(w io.Writer, alias string, id int32) {
	io.WriteString(w, ` AS "`)
	io.WriteString(w, alias)
	io.WriteString(w, `_`)
	int2string(w, id)
	io.WriteString(w, `"`)
}

func colWithTable(w io.Writer, table, col string) {
	io.WriteString(w, `"`)
	io.WriteString(w, table)
	io.WriteString(w, `"."`)
	io.WriteString(w, col)
	io.WriteString(w, `"`)
}

func colWithTableID(w io.Writer, table string, id int32, col string) {
	io.WriteString(w, `"`)
	io.WriteString(w, table)
	if id >= 0 {
		io.WriteString(w, `_`)
		int2string(w, id)
	}
	io.WriteString(w, `"."`)
	io.WriteString(w, col)
	io.WriteString(w, `"`)
}

func quoted(w io.Writer, identifier string) {
	io.WriteString(w, `"`)
	io.WriteString(w, identifier)
	io.WriteString(w, `"`)
}

func squoted(w io.Writer, identifier string) {
	io.WriteString(w, `'`)
	io.WriteString(w, identifier)
	io.WriteString(w, `'`)
}

const charset = "0123456789"

func int2string(w io.Writer, val int32) {
	if val < 10 {
		w.Write([]byte{charset[val]})
		return
	}

	temp := int32(0)
	val2 := val
	for val2 > 0 {
		temp *= 10
		temp += val2 % 10
		val2 = int32(float64(val2 / 10))
	}

	val3 := temp
	for val3 > 0 {
		d := val3 % 10
		val3 /= 10
		w.Write([]byte{charset[d]})
	}
}