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psql.go
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psql.go
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// src/go/psql.go 2017-9-11 Alan U. Kennington.
// $Id: src/go/psql.go 90a610140f 2017-09-11 08:52:18Z Alan U. Kennington $
// PostgreSQL query builder.
// Using version go1.1.2.
// PostgreSQL version 8.0.3.
/*-------------------------------------------------------------------------
Functions in this package.
psql_expr_node{}
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_parent::
psql_expr_parent::getParent
psql_expr_parent::setParent
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_str::
psql_expr_str::clone
psql_expr_str::Set
psql_expr_str::Build
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_num::
psql_expr_num::clone
psql_expr_num::Set
psql_expr_num::Build
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_field::
psql_expr_field::clone
psql_expr_field::Set
psql_expr_field::String
psql_expr_field::Build
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_op::
psql_expr_op::clone
psql_expr_op::Clear
psql_expr_op::Set
psql_expr_op::Build
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_fn::
psql_expr_fn::clone
psql_expr_fn::Clear
psql_expr_fn::ArgCount
psql_expr_fn::ArgCountValid
psql_expr_fn::Set
psql_expr_fn::Build
---------------------------------------------------------------------------
Psql_expr::
Psql_expr::setNode
Psql_expr::getNode
Psql_expr::SetStr
Psql_expr::SetNum
Psql_expr::SetFld
Psql_expr::SetOp
Psql_expr::SetFn
Psql_expr::Clone
Psql_expr::Build
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Xstr
Xnum
Xfld
Xop
Xfn
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
psql_expr_as::
psql_expr_as::Set
psql_expr_as::Build
---------------------------------------------------------------------------
psql_from_node{}
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psql_from_table::
psql_from_table::getParent
psql_from_table::setParent
psql_from_table::Set
psql_from_table::SetOnly
psql_from_table::Build
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psql_from_item::
psql_from_item::Set
psql_from_item::Build
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Psql_from::
Psql_from::setNode
Psql_from::SetTable
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Xtable
---------------------------------------------------------------------------
psql_order::
psql_order::SetDirn
psql_order::Set
psql_order::SetDesc
psql_order::Build
---------------------------------------------------------------------------
psql_limit::
psql_limit::Set
psql_limit::Build
---------------------------------------------------------------------------
Psql_select::
Psql_select::Clear
Psql_select::SelectAppendStrAs
Psql_select::SelectAppendStr
Psql_select::SelectAppendNumAs
Psql_select::SelectAppendNum
Psql_select::SelectAppendFldAs
Psql_select::SelectAppendFld
Psql_select::SelectAppendOpAs
Psql_select::SelectAppendOp
Psql_select::SelectAppendFnAs
Psql_select::SelectAppendFn
Psql_select::SelectAppendExprAs
Psql_select::SelectAppendExpr
Psql_select::SelectAppendExprs
Psql_select::SelectBuild
Psql_select::FromAppendItem
Psql_select::FromBuild
Psql_select::WhereSetExpr
Psql_select::OrderAppendDirn
Psql_select::OrderAppend
Psql_select::OrderAppendDesc
Psql_select::OrderBuild
Psql_select::LimitSet
Psql_select::Build
-------------------------------------------------------------------------*/
/*
This Go-package builds PostgreSQL query strings safely and conveniently.
The convenience is most noticeable for very long complex queries. The safety is
essential for preventing SQL injections. In principle, no SQL should ever be
written by hand. The SQL language is too dangerous!
*/
package psqlbuild
// External libraries.
import "fmt"
// import "net/http"
// import "log"
// import "io"
// import "time"
import "strings"
import "strconv"
// import "errors"
// import . "localhost/s2list"
import . "github.com/drauk/s2list"
// import "localhost/elist"
import "github.com/drauk/elist"
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
const formatFloat string = "%.17g"
//=============================================================================
//=============================================================================
/*
Common interface for all expression tree-nodes.
Union of *psql_expr_str/num/field/op/fn.
*/
type psql_expr_node interface {
//----------------------//
// psql_expr_node{} //
//----------------------//
getParent() psql_expr_node
setParent(psql_expr_node)
Build() (string, error)
} // End of interface psql_expr_node.
//=============================================================================
//=============================================================================
/*
Parent class to be embedded in all psql_expr_node classes.
This is effectively a parent-class for all psql_expr_node classes.
So the code for setParent() and getParent() doesn't need multiple copies.
*/
type psql_expr_parent struct {
//----------------------//
// psql_expr_parent:: //
//----------------------//
parent psql_expr_node
}
func (p *psql_expr_parent) getParent() psql_expr_node {
//------------------------------//
// psql_expr_parent::getParent //
//------------------------------//
if p == nil {
return nil
}
return p.parent
} // End of function psql_expr_parent::getParent.
func (p *psql_expr_parent) setParent(q psql_expr_node) {
//------------------------------//
// psql_expr_parent::setParent //
//------------------------------//
if p == nil {
return
}
p.parent = q
} // End of function psql_expr_parent::setParent.
//=============================================================================
//=============================================================================
/*
Literal string, which must be quoted in the PostgreSQL style.
*/
type psql_expr_str struct {
//----------------------//
// psql_expr_str:: //
//----------------------//
val string // Literal string. Will be quoted carefully.
psql_expr_parent
}
/*
Clone a string expression.
*/
func (p *psql_expr_str) clone() *psql_expr_str {
//----------------------//
// psql_expr_str::clone //
//----------------------//
if p == nil {
return nil
}
q := new(psql_expr_str)
q.val = p.val
return q
} // End of function psql_expr_str::clone.
/*
Set a constant string expression.
*/
func (p *psql_expr_str) Set(s string) error {
//----------------------//
// psql_expr_str::Set //
//----------------------//
if p == nil {
return elist.New("psql_expr_str::Set: p == nil")
}
p.val = s
return nil
} // End of function psql_expr_str::Set.
/*
For the Postgres standard for string escape characters, see:
https://www.postgresql.org/docs/8.0/static/sql-syntax.html#SQL-SYNTAX-CONSTANTS
*/
func (p *psql_expr_str) Build() (string, error) {
//--------------------------//
// psql_expr_str::Build //
//--------------------------//
if p == nil {
return "", elist.New("psql_expr_str::Build: p == nil")
}
var str string
// The extremely important rule for PostgreSQL strings.
// This is where the SQL injections are (hopefully) defeated!
// old: var rep = strings.NewReplacer("'", "\'", `"`, `\"`, `\`, `\\`);
var rep = strings.NewReplacer("'", "''", `\`, `\\`)
str = fmt.Sprintf("'%s'", rep.Replace(p.val))
return str, nil
} // End of function psql_expr_str::Build.
//=============================================================================
//=============================================================================
/*
A numerical expression value is inserted into SQL queries as a string.
The validity of that string _must_ be verified before setting the
member "val" of psql_expr_num.
*/
type psql_expr_num struct {
//----------------------//
// psql_expr_num:: //
//----------------------//
val string // String representing a number.
psql_expr_parent
}
/*
Clone a number expression.
*/
func (p *psql_expr_num) clone() *psql_expr_num {
//----------------------//
// psql_expr_num::clone //
//----------------------//
if p == nil {
return nil
}
q := new(psql_expr_num)
q.val = p.val
return q
} // End of function psql_expr_num::clone.
/*
Set a constant numerical expression.
The argument "v" may be an integer, float64 or a string which represents
an integer or floating-point constant.
For PostgreSQL numeric constants, see
https://www.postgresql.org/docs/8.0/static/sql-syntax.html#SQL-SYNTAX-CONSTANTS
See section 4.1.2.4 "Numeric constants".
digits
digits.[digits][e[+-]digits]
[digits].digits[e[+-]digits]
digits e[+-]digits
*/
func (p *psql_expr_num) Set(v interface{}) error {
//----------------------//
// psql_expr_num::Set //
//----------------------//
if p == nil {
return elist.New("psql_expr_num::Set: p == nil")
}
var str string
switch x := v.(type) {
// There must be a better way to do these 12 cases!!!
case int:
str = fmt.Sprintf("%d", x)
case int8:
str = fmt.Sprintf("%d", x)
case int16:
str = fmt.Sprintf("%d", x)
case int32:
str = fmt.Sprintf("%d", x)
case int64:
str = fmt.Sprintf("%d", x)
case uint:
str = fmt.Sprintf("%d", x)
case uint8:
str = fmt.Sprintf("%d", x)
case uint16:
str = fmt.Sprintf("%d", x)
case uint32:
str = fmt.Sprintf("%d", x)
case uint64:
str = fmt.Sprintf("%d", x)
case float32:
// NOTE: Should check that the Go-format is acceptable to PostgreSQL.
str = fmt.Sprintf(formatFloat, x)
case float64:
// NOTE: Should check that the Go-format is acceptable to PostgreSQL.
str = fmt.Sprintf(formatFloat, x)
case string:
// Test whether this is a genuine numerical string.
// Testing for integer format is probably fairly safe.
var E error
_, E = strconv.ParseInt(x, 10, 0)
if E == nil {
str = x
break
}
// Testing for float format is probably not so safe.
// A valid Go-format might not be a valid PostgreSQL-format.
_, E = strconv.ParseFloat(x, 64)
if E == nil {
str = x
break
}
return elist.New(
"psql_expr_num::Set: string does not represent a number")
default:
return elist.New("psql_expr_num::Set: string equals nil")
}
p.val = str
return nil
} // End of function psql_expr_num::Set.
/*
This function trusts that the string parameter is a valid PostgreSQL number.
Otherwise, SQL injections may occur!
*/
func (p *psql_expr_num) Build() (string, error) {
//--------------------------//
// psql_expr_num::Build //
//--------------------------//
if p == nil {
return "", elist.New("psql_expr_num::Build: p == nil")
}
return p.val, nil
} // End of function psql_expr_num::Build.
//=============================================================================
//=============================================================================
/*
Table name syntax is described here.
https://www.postgresql.org/docs/8.0/static/sql-syntax.html
PostgreSQL value-expressions are described here:
https://www.postgresql.org/docs/8.0/static/sql-expressions.html
*/
type psql_expr_field struct {
//----------------------//
// psql_expr_field:: //
//----------------------//
tab string // Table name. Empty to indicate not set.
fld string // The field (i.e. column name) of a table.
psql_expr_parent
}
/*
Clone a field expression.
*/
func (p *psql_expr_field) clone() *psql_expr_field {
//--------------------------//
// psql_expr_field::clone //
//--------------------------//
if p == nil {
return nil
}
q := new(psql_expr_field)
q.tab = p.tab
q.fld = p.fld
return q
} // End of function psql_expr_field::clone.
func (p *psql_expr_field) Set(tab string, fld string) error {
//----------------------//
// psql_expr_field::Set //
//----------------------//
if p == nil {
return elist.New("psql_expr_field::Set: p == nil")
}
p.tab = tab
p.fld = fld
return nil
} // End of function psql_expr_field::Set.
/*
psql_expr_field::String only returns a string representation of this object
for diagnostic purposes.
Not for use in SQL query building!
*/
func (p *psql_expr_field) String() string {
//--------------------------//
// psql_expr_field::String //
//--------------------------//
if p == nil {
return ""
}
return fmt.Sprintf("(table: \"%s\", field: \"%s\")", p.tab, p.fld)
} // End of function psql_expr_field::String.
/*
Build a single field for an SQL query.
https://www.postgresql.org/docs/8.0/static/sql-select.html#SQL-SELECT-LIST
This routine replaces '"' with '""' to fit the lexical rules for identifiers.
https://www.postgresql.org/docs/8.0/static/sql-syntax.html
"Quoted identifiers can contain any character other than a double quote itself.
(To include a double quote, write two double quotes.) This allows constructing
table or column names that would otherwise not be possible, such as ones
containing spaces or ampersands."
*/
func (p *psql_expr_field) Build() (string, error) {
//--------------------------//
// psql_expr_field::Build //
//--------------------------//
if p == nil {
return "", elist.New("psql_expr_num::Set: p == nil")
}
// The field (i.e. column) identifier must be non-empty.
if p.fld == "" {
return "", elist.New("psql_expr_num::Set: p.fld == nil")
}
// The rule for PostgreSQL identifiers is that double-quote is repeated.
var rep = strings.NewReplacer(`"`, `""`)
var res, tab string
if p.tab != "" {
tab = fmt.Sprintf("\"%s\".", rep.Replace(p.tab))
}
res = fmt.Sprintf("%s\"%s\"", tab, rep.Replace(p.fld))
return res, nil
} // End of function psql_expr_field::Build.
//=============================================================================
//=============================================================================
type psql_expr_op struct {
//----------------------//
// psql_expr_op:: //
//----------------------//
op string // The binary or unary operation.
left psql_expr_node // The left sub-expression.
right psql_expr_node // The right sub-expression.
psql_expr_parent
}
/*
Clone an operator expression.
*/
func (p *psql_expr_op) clone() *psql_expr_op {
//----------------------//
// psql_expr_op::clone //
//----------------------//
if p == nil {
return nil
}
q := new(psql_expr_op)
q.op = p.op
// Clone the left sub-expression recursively.
switch x := p.left.(type) {
case *psql_expr_str:
q.left = x.clone()
case *psql_expr_num:
q.left = x.clone()
case *psql_expr_field:
q.left = x.clone()
case *psql_expr_op:
q.left = x.clone()
case *psql_expr_fn:
// NOTE: To be defined!
q.left = x.clone()
case nil:
default:
// "None of the above" is an error.
return nil
}
// Clone the right sub-expression recursively.
switch x := p.right.(type) {
case *psql_expr_str:
q.right = x.clone()
case *psql_expr_num:
q.right = x.clone()
case *psql_expr_field:
q.right = x.clone()
case *psql_expr_op:
q.right = x.clone()
case *psql_expr_fn:
// NOTE: To be defined!
q.right = x.clone()
case nil:
default:
// "None of the above" is an error.
return nil
}
return q
} // End of function psql_expr_op::clone.
func (p *psql_expr_op) Clear() error {
//----------------------//
// psql_expr_op::Clear //
//----------------------//
if p == nil {
return elist.New("psql_expr_op::Clear: p == nil")
}
p.op = ""
p.left = nil
p.right = nil
return nil
} // End of function psql_expr_op::Clear.
/*
This function makes only a very rudimentary check of the correctness of
the specified operator expression.
It has many false positives and false negatives.
So don't open up this function to users, especially hackers!
It should at least accept most correct operator-expressions for my purposes.
Logic operators:
https://www.postgresql.org/docs/8.0/static/functions.html#FUNCTIONS-LOGICAL
Possible characters in operators:
https://www.postgresql.org/docs/8.0/static/sql-syntax.html#SQL-SYNTAX-OPERATORS
+ - * / < > = ~ ! @ # % ^ & | ` ?
*/
func (p *psql_expr_op) Set(op string,
//----------------------//
// psql_expr_op::Set //
//----------------------//
lft psql_expr_node, rt psql_expr_node) error {
if p == nil {
return elist.New("psql_expr_op::Set: p == nil")
}
p.Clear()
// Check binary operators.
if lft != nil && rt != nil {
switch op {
// Infix operators. Arithmetic.
case "+", "-", "*", "/", "%", "^":
// Comparison.
case "=", "<", ">", "<=", ">=", "<>", "!=":
// String matching.
case "~", "~*", "!~", "!~*":
// String or bit-string concatenation.
case "||":
// Bit-string operations.
case "&", "|", "<<", ">>", "#":
// Logic. Should be a case-independent test!
case "and", "or", "AND", "OR":
default:
return elist.Newf(
"psql_expr_op::Set: bad binary operator \"%s\"", op)
}
// Check prefix operators.
} else if lft == nil && rt != nil {
switch op {
// Arithmetic.
case "+", "-":
// Bit-string operations.
case "~":
// Logic. Should be a case-independent test!
case "not", "NOT":
default:
return elist.Newf(
"psql_expr_op::Set: bad prefix operator \"%s\"", op)
}
} else {
return elist.New("psql_expr_op::Set: left/right nil combination")
}
// Set the parent links.
if lft != nil {
lft.setParent(p)
}
if rt != nil {
rt.setParent(p)
}
p.op = op
p.left = lft
p.right = rt
return nil
} // End of function psql_expr_op::Set.
/*
This function must recursively traverse the expression tree.
It is assumed that the operator and the left/right expressions are valid.
Only prefix-unary and infix-binary operators are implemented here.
*/
func (p *psql_expr_op) Build() (string, error) {
//----------------------//
// psql_expr_op::Build //
//----------------------//
if p == nil {
return "", elist.New("psql_expr_op::Set: p == nil")
}
if p.op == "" {
return "", elist.New("psql_expr_op::Set: p.op == nil")
}
var E error
var lft, rt, result string
// Build the left expression.
if p.left != nil {
lft, E = p.left.Build()
if E != nil {
return "", elist.Push(E, "psql_expr_op::Build: p.left.Build()")
}
}
// Build the right expression.
if p.right != nil {
rt, E = p.right.Build()
if E != nil {
return "", elist.Push(E, "psql_expr_op::Build: p.right.Build()")
}
}
// Construct the resultant query expression.
if p.left == nil && p.right != nil {
// Prefix-unary case.
result = fmt.Sprintf("%s(%s)", p.op, rt)
} else if p.left != nil && p.right != nil {
// Infix-binary case.
result = fmt.Sprintf("(%s) %s (%s)", lft, p.op, rt)
} else {
return "", elist.New("psql_expr_op::Set: wrong left/right nil mix")
}
return result, nil
} // End of function psql_expr_op::Build.
//=============================================================================
//=============================================================================
/*
The function name must be a non-empty string, which apparently
must contain only ASCII letters and underscores.
https://www.postgresql.org/docs/8.0/static/functions.html
But probably user-defined functions can be virtually any kind of string.
https://www.postgresql.org/docs/8.0/static/sql-createfunction.html
Putting double-quotes around function names seems to be the right thing to do!
The name-formation-rules for identifiers and key words probably apply here.
https://
www.postgresql.org/docs/8.0/static/sql-syntax.html#SQL-SYNTAX-IDENTIFIERS
Thus initial character is a letter or underscore, but letters can be non-Latin.
Other letters may also be digits or dollar signs.
*/
type psql_expr_fn struct {
//----------------------//
// psql_expr_fn:: //
//----------------------//
fn string // The function name.
args List_base // The function arguments.
psql_expr_parent
}
/*
Clone a function expression.
*/
func (p *psql_expr_fn) clone() *psql_expr_fn {
//----------------------//
// psql_expr_fn::clone //
//----------------------//
if p == nil {
return nil
}
q := new(psql_expr_fn)
q.fn = p.fn
// Some functions may have zero arguments.
if p.args.Empty() {
return q
}
var E error
var iter List_iter
var curr *List_node
E = iter.Init(&p.args)
if E != nil {
return nil
}
for curr, E = iter.Next(); curr != nil; curr, E = iter.Next() {
if E != nil {
return nil
}
var v interface{}
v, E = curr.GetValue()
if E != nil {
return nil
}
// Construct a clone from each argument.
switch x := v.(type) {
case *psql_expr_str:
arg := x.clone()
if arg == nil {
return nil
}
E = q.args.AppendValue(arg)
if E != nil {
return nil
}
case *psql_expr_num:
arg := x.clone()
if arg == nil {
return nil
}
E = q.args.AppendValue(arg)
if E != nil {
return nil
}
case *psql_expr_field:
arg := x.clone()
if arg == nil {
return nil
}
E = q.args.AppendValue(arg)
if E != nil {
return nil
}
case *psql_expr_op:
// This is recursive!
arg := x.clone()
if arg == nil {
return nil
}
E = q.args.AppendValue(arg)
if E != nil {
return nil
}
case *psql_expr_fn:
// This is recursive!
arg := x.clone()
if arg == nil {
return nil
}
E = q.args.AppendValue(arg)
if E != nil {
return nil
}
case nil:
// A correct function must have no nil-arguments.
return nil
default:
// "None of the above" is an error.
return nil
}
// Set the parent node.
pnode, ok := v.(psql_expr_node)
if !ok {
return nil
}
pnode.setParent(q)
}
return q
} // End of function psql_expr_fn::clone.
func (p *psql_expr_fn) Clear() error {
//----------------------//
// psql_expr_fn::Clear //
//----------------------//
if p == nil {
return elist.New("psql_expr_fn::Clear: p == nil")
}
var E error
p.fn = ""
E = p.args.Clear()
if E != nil {
return elist.Push(E, "psql_expr_fn::Clear: p == nil")
}
return nil
} // End of function psql_expr_fn::Clear.
/*
Return the current number of arguments.
*/
func (p *psql_expr_fn) ArgCount() int {
//--------------------------//
// psql_expr_fn::ArgCount //
//--------------------------//
if p == nil {
return 0
}
return p.args.Length()
} // End of function psql_expr_fn::ArgCount.
/*
Return the current nil/wrong/total numbers of arguments.
*/
func (p *psql_expr_fn) ArgCountValid() (int, int, int) {
//------------------------------//
// psql_expr_fn::ArgCountValid //
//------------------------------//
if p == nil {
return 0, 0, 0
}
return p.args.ValidLength()
} // End of function psql_expr_fn::ArgCountValid.
func (p *psql_expr_fn) Set(name string, args ...psql_expr_node) error {
//----------------------//
// psql_expr_fn::Set //
//----------------------//
if p == nil {
return elist.New("psql_expr_fn::Set: p == nil")
}
var E error
E = p.Clear()
if E != nil {
return elist.New("psql_expr_fn::Set: p.Clear()")
}
p.fn = name
// Some functions may have zero arguments.
if args == nil {
return nil
}
// Some functions may have one or more arguments.
for _, q := range args {
if q == nil {
return elist.New("psql_expr_fn::Set: range args")
}
E = p.args.AppendValue(q)
if E != nil {
return elist.Push(E, "psql_expr_fn::Set: p.args.AppendValue()")
}
q.setParent(p)
}
return nil
} // End of function psql_expr_fn::Set.
/*
This function must recursively traverse the expression tree.
It is assumed that the function name and the argument expressions are valid.
*/
func (p *psql_expr_fn) Build() (string, error) {
//----------------------//
// psql_expr_fn::Build //
//----------------------//
if p == nil {
return "", elist.New("psql_expr_fn::Build: p == nil")
}
if p.fn == "" {
return "", elist.New("psql_expr_fn::Build: p.fn == nil")
}
// The rule for PostgreSQL identifiers is that double-quote is repeated.
var rep = strings.NewReplacer(`"`, `""`)
var result string
result = fmt.Sprintf("\"%s\"(", rep.Replace(p.fn))
var E error
var iter List_iter
var curr *List_node
E = iter.Init(&p.args)
if E != nil {
return "", elist.Push(E, "psql_expr_fn::Build: iter.Init()")
}
var nloop int = 0
var arg string
for curr, E = iter.Next(); curr != nil; curr, E = iter.Next() {
if E != nil {
return "", elist.Push(E, "psql_expr_fn::Build: iter.Next()")
}
if nloop > 0 {
// The space is really optional, but it looks better!
result += ", "
}
nloop += 1
var v interface{}
v, E = curr.GetValue()
if E != nil {
return "", elist.Push(E, "psql_expr_fn::Build: curr.GetValue()")
}
// Build the string.
pnode, ok := v.(psql_expr_node)
if !ok {
return "", elist.New("psql_expr_fn::Build: v.(psql_expr_node)")
}
arg, E = pnode.Build()
if E != nil {
return "", elist.Push(E, "psql_expr_fn::Build: pnode.Build()")
}
// Parentheses are never needed for arguments of functions.
// result += "(" + arg + ")";
result += arg
}
result += ")"
return result, nil
} // End of function psql_expr_fn::Build.
//=============================================================================
//=============================================================================
/*
This is the expression-object which the user of this package will receive.
A Psql_expr object is a PostgreSQL expression or sub-expression.
The member "node" is an opaque handle.
So a Pqsl_expr object may be freely copied.
The error field E is public so that users can inspect it.
*/
type Psql_expr struct {
//----------------------//
// Psql_expr:: //
//----------------------//
/*------------------------------------------------------------------------------
NOTE: Maybe E should be private to prevent modification??
The error is always set to the same as the return value of a function.
So E is only useful to inform functions whose arguments are outputs
from Xstr, Xnum, Xfld, Xop and Xfn of the error stack which has occurred.
In other words, the E field is a copy (or shadow) of the last error
returned by a member function of Psql_expr::.
------------------------------------------------------------------------------*/
node psql_expr_node // Union of *psql_expr_str/num/field/op/fn.
E error // A copy of the error returned by functions.
}
func (p *Psql_expr) setNode(node psql_expr_node) error {
//----------------------//
// Psql_expr::setNode //
//----------------------//
if p == nil {
return elist.New("Psql_expr::setNode: p == nil")
}
// Don't allow re-set of a non-nil value.
if p.node != nil {
p.E = elist.New("Psql_expr::setNode: p.node == nil")
return p.E
}
// Don't allow setting to a nil value.
if node == nil {
p.E = elist.New("Psql_expr::setNode: node == nil")
return p.E
}
p.node = node
p.E = nil
return nil
} // End of function Psql_expr::setNode.
func (p *Psql_expr) getNode() psql_expr_node {
//----------------------//
// Psql_expr::getNode //