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FB-1800: Implement SUBSTRING() (#2343)

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substring(string, startIndex,length).
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rachithrr 2022-12-09 05:20:15 +05:30 • committed by GitHub
parent 728b1dc9f5
commit aa2a62fda0
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4 changed files with 150 additions and 0 deletions
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2
sql3/planner/expression.go
View file

@ -1478,6 +1478,8 @@ func (n *callPlanExpression) Evaluate(currentRow []interface{}) (interface{}, er
return n.EvaluateDatepart(currentRow)
case "REVERSE":
return n.EvaluateReverse(currentRow)
case "SUBSTRING":
return n.EvaluateSubstring(currentRow)
default:
return nil, sql3.NewErrInternalf("unhandled function name '%s'", n.name)
}

2
sql3/planner/expressionanalyzercall.go
View file

@ -243,6 +243,8 @@ func (p *ExecutionPlanner) analyzeCallExpression(call *parser.Call, scope parser
return p.analyzeFunctionSubtable(call, scope)
case "REVERSE":
return p.analyseFunctionReverse(call, scope)
case "SUBSTRING":
return p.analyseFunctionSubstring(call, scope)
default:
return nil, sql3.NewErrCallUnknownFunction(call.Name.NamePos.Line, call.Name.NamePos.Column, call.Name.Name)

67
sql3/planner/inbuiltfunctionsstring.go
View file

@ -1,6 +1,8 @@
package planner
import (
"strconv"
"github.com/molecula/featurebase/v3/sql3"
"github.com/molecula/featurebase/v3/sql3/parser"
)
@ -20,6 +22,27 @@ func (p *ExecutionPlanner) analyseFunctionReverse(call *parser.Call, scope parse
return call, nil
}
func (p *ExecutionPlanner) analyseFunctionSubstring(call *parser.Call, scope parser.Statement) (parser.Expr, error) {
if len(call.Args) <= 1 || len(call.Args) > 3 {
return nil, sql3.NewErrCallParameterCountMismatch(call.Rparen.Line, call.Rparen.Column, call.Name.Name, 2, len(call.Args))
}
if !typeIsString(call.Args[0].DataType()) {
return nil, sql3.NewErrStringExpressionExpected(call.Args[0].Pos().Line, call.Args[0].Pos().Column)
}
// the third parameter is optional
for i := 1; i < len(call.Args); i++ {
if !typeIsInteger(call.Args[i].DataType()) {
return nil, sql3.NewErrIntExpressionExpected(call.Args[i].Pos().Line, call.Args[i].Pos().Column)
}
}
call.ResultDataType = parser.NewDataTypeString()
return call, nil
}
// reverses the string
func (n *callPlanExpression) EvaluateReverse(currentRow []interface{}) (interface{}, error) {
argOneEval, err := n.args[0].Evaluate(currentRow)
@ -39,3 +62,47 @@ func (n *callPlanExpression) EvaluateReverse(currentRow []interface{}) (interfac
}
return string(runes), nil
}
// Takes string, startIndex and length and returns the substring.
func (n *callPlanExpression) EvaluateSubstring(currentRow []interface{}) (interface{}, error) {
argOneEval, err := n.args[0].Evaluate(currentRow)
if err != nil {
return nil, err
}
stringArgOne, ok := argOneEval.(string)
if !ok {
return nil, sql3.NewErrInternalf("unexpected type converion %T", argOneEval)
}
// this takes a sliding window approach to evaluate substring.
startIndex, err := strconv.Atoi(n.args[1].String())
if err != nil {
return nil, sql3.NewErrInternalf("unexpected type converion %T", n.args[1])
}
if startIndex >= len(stringArgOne) {
return "", nil
}
endIndex := len(stringArgOne)
if len(n.args) > 2 {
ln, err := strconv.Atoi(n.args[2].String())
if err != nil {
return nil, sql3.NewErrInternalf("unexpected type converion %T", n.args[1])
}
endIndex = startIndex + ln
}
if endIndex < 0 {
return "", nil
}
if startIndex < 0 {
startIndex = 0
}
if endIndex > len(stringArgOne) {
return stringArgOne[startIndex:], nil
}
return stringArgOne[startIndex:endIndex], nil
}

79
sql3/test/defs/defs_string_functions.go
View file

@ -17,6 +17,7 @@ var stringScalarFunctionsTests = TableTest{
),
SQLTests: []SQLTest{
{
name: "ReverseString",
SQLs: sqls(
"select reverse('this')",
),
@ -28,5 +29,83 @@ var stringScalarFunctionsTests = TableTest{
),
Compare: CompareExactUnordered,
},
{
name: "ReverseReverseString",
SQLs: sqls(
"select reverse(reverse('this'))",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("this")),
),
Compare: CompareExactUnordered,
},
{
name: "SubstringPositiveIndex",
SQLs: sqls(
"select substring('testing', 1, 3)",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("est")),
),
Compare: CompareExactUnordered,
},
{
name: "SubstringNegativeIndex",
SQLs: sqls(
"select substring('testing', -10, 14)",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("test")),
),
Compare: CompareExactUnordered,
},
{
name: "SubstringNoLength",
SQLs: sqls(
"select substring('testing', -5)",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("testing")),
),
Compare: CompareExactUnordered,
},
{
name: "ReverseSubstring",
SQLs: sqls(
"select reverse(substring('testing', 0))",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("gnitset")),
),
Compare: CompareExactUnordered,
},
{
name: "SubstringReverse",
SQLs: sqls(
"select substring(reverse('testing'), 3)",
),
ExpHdrs: hdrs(
hdr("", fldTypeString),
),
ExpRows: rows(
row(string("tset")),
),
Compare: CompareExactUnordered,
},
},
}