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Merged
angelamayxie merged 8 commits into from
Feb 2, 2026
+136 −67
Merged

Calculate month and quarter for timestampdiff based on date and clock time values #3409

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1b74d4a
rewrite month diff
angelamayxie Jan 31, 2026
0eea689
refactor month diff into reusable function for year and quarter
angelamayxie Jan 31, 2026
df431af
add tests
angelamayxie Jan 31, 2026
f301126
add tests for timestamp diff between smallest and largest timestamps
angelamayxie Jan 31, 2026
e0b9292
rename monthDiff to monthsDiff
angelamayxie Jan 31, 2026
3dab6b7
refactor dateDiff calculation to be more performant
angelamayxie Jan 31, 2026
0fbede9
account for year differences where a whole year has not elapsed
angelamayxie Jan 31, 2026
a27201f
revert back to monthsDiff
angelamayxie Feb 2, 2026
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98 changes: 97 additions & 1 deletion enginetest/queries/function_queries.go
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Original file line number Diff line number Diff line change
Expand Up @@ -911,7 +911,7 @@ var FunctionQueryTests = []QueryTest{
Query: "SELECT TIMESTAMPDIFF(SECOND, null, '2007-12-31 00:00:00');",
Expected: []sql.Row{{nil}},
},
// https://github.com/dolthub/dolt/issues/10393
// TIMESTAMPDIFF YEAR tests https://github.com/dolthub/dolt/issues/10393
{
Query: "SELECT TIMESTAMPDIFF(YEAR, DATE '2011-07-05', DATE '2026-07-04')",
Expected: []sql.Row{{14}},
Expand All @@ -936,6 +936,102 @@ var FunctionQueryTests = []QueryTest{
Query: "SELECT TIMESTAMPDIFF(YEAR, DATE '2026-07-03', DATE '2025-07-04')",
Expected: []sql.Row{{0}},
},
{
Query: `select timestampdiff(year, "0050-01-01", "2020-01-01");`,
Expected: []sql.Row{{1970}},
},
{
Query: "select timestampdiff(year, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{9999}},
},
// TIMESTAMPDIFF MONTH tests https://github.com/dolthub/dolt/issues/10393
{
Query: `select timestampdiff(year, "2000-12-25", "2020-2-20");`,
Expected: []sql.Row{{19}},
},
{
Query: "SELECT TIMESTAMPDIFF(month, DATE '2011-07-05', DATE '2026-07-04')",
Expected: []sql.Row{{179}},
},
{
Query: "SELECT TIMESTAMPDIFF(month, DATE '2026-07-04', DATE '2011-07-05')",
Expected: []sql.Row{{-179}},
},
{
Query: `select timestampdiff(month, "2000-12-25", "2020-2-20");`,
Expected: []sql.Row{{229}},
},
{
Query: `select timestampdiff(month, "0050-01-01", "2020-01-01");`,
Expected: []sql.Row{{23640}},
},
{
Query: "select timestampdiff(month, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{119999}},
},
// TIMESTAMPDIFF QUARTER tests https://github.com/dolthub/dolt/issues/10393
{
Query: "SELECT TIMESTAMPDIFF(quarter, DATE '2011-07-05', DATE '2026-07-04')",
Expected: []sql.Row{{59}},
},
{
Query: "SELECT TIMESTAMPDIFF(quarter, DATE '2026-07-04', DATE '2011-07-05')",
Expected: []sql.Row{{-59}},
},
{
Query: `select timestampdiff(quarter, "0050-01-01", "2020-01-01");`,
Expected: []sql.Row{{7880}},
},
{
Query: `select timestampdiff(quarter, "2000-12-25", "2020-2-20");`,
Expected: []sql.Row{{76}},
},
{
Query: "select timestampdiff(quarter, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{39999}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL
Query: "select timestampdiff(microsecond, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{315569433599999999}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL
Query: "select timestampdiff(second, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{315569433599}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL
Query: "select timestampdiff(minute, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{5259490559}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL
Query: "select timestampdiff(hour, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{87658175}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL

@jycor jycor Feb 2, 2026

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what a tragedy

Query: "select timestampdiff(day, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{3652423}},
},
{
// https://github.com/dolthub/dolt/issues/10397
Skip: true,
// might need to change first date to 0001-01-01 since 0000 is a leap year in Go but not in MySQL
Query: "select timestampdiff(week, '0000-01-01', '9999-12-31 23:59:59.999999');",
Expected: []sql.Row{{521774}},
},
// TRIM Function Tests
{
Query: `SELECT TRIM(mytable.s) AS s FROM mytable`,
Expand Down
116 changes: 50 additions & 66 deletions sql/expression/function/time_math.go
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Original file line number Diff line number Diff line change
Expand Up @@ -669,10 +669,10 @@ func (t *TimestampDiff) Eval(ctx *sql.Context, row sql.Row) (interface{}, error)

unit = strings.TrimPrefix(strings.ToLower(unit.(string)), "sql_tsi_")

date1 := expr1.(time.Time)
date2 := expr2.(time.Time)
time1 := expr1.(time.Time)
time2 := expr2.(time.Time)

diff := date2.Sub(date1)
diff := time2.Sub(time1)

var res int64
switch unit {
Expand All @@ -689,74 +689,58 @@ func (t *TimestampDiff) Eval(ctx *sql.Context, row sql.Row) (interface{}, error)
case "week":
res = int64(diff.Hours() / (24 * 7))
case "month":
// TODO: this calculation is not correct. Not every month is 30 days https://github.com/dolthub/dolt/issues/10393
res = int64(diff.Hours() / (24 * 30))
if res > 0 {
if date2.Day()-date1.Day() < 0 {
res -= 1
} else if date2.Hour()-date1.Hour() < 0 {
res -= 1
} else if date2.Minute()-date1.Minute() < 0 {
res -= 1
} else if date2.Second()-date1.Second() < 0 {
res -= 1
}
}
res = dateDiff(time1, time2, false)
case "quarter":
// TODO: this calculation is not correct. Not every month is 30 days https://github.com/dolthub/dolt/issues/10393
monthRes := int64(diff.Hours() / (24 * 30))
if monthRes > 0 {
if date2.Day()-date1.Day() < 0 {
monthRes -= 1
} else if date2.Hour()-date1.Hour() < 0 {
monthRes -= 1
} else if date2.Minute()-date1.Minute() < 0 {
monthRes -= 1
} else if date2.Second()-date1.Second() < 0 {
monthRes -= 1
}
}
res = monthRes / 3
res = dateDiff(time1, time2, false) / 3
case "year":
if diff == 0 {
return 0, nil
}
negate := false
before := date1
after := date2
if diff < 0 {
negate = true
before = date2
after = date1
}

beforeYear, beforeMonth, beforeDay := before.Date()
afterYear, afterMonth, afterDay := after.Date()
yearDiff := afterYear - beforeYear
if beforeMonth > afterMonth {
yearDiff -= 1
} else if beforeMonth == afterMonth {
if beforeDay > afterDay {
yearDiff -= 1
} else if beforeDay == afterDay {
beforeHour, beforeMin, beforeSec := before.Clock()
afterHour, afterMin, afterSec := after.Clock()
secondDiff := (afterHour-beforeHour)*3600 + (afterMin-beforeMin)*60 + (afterSec - beforeSec)
if secondDiff < 0 {
yearDiff -= 1
} else if secondDiff == 0 && before.Nanosecond() > after.Nanosecond() {
yearDiff -= 1
}
}
}

res = int64(yearDiff)
if negate {
res = -res
}
res = dateDiff(time1, time2, true)
default:
return nil, errors.NewKind("invalid interval unit: %s").New(unit)
}

return res, nil
}

// dateDiff calculates the difference between two time.Times based on their Date and Clock values. If yearDiff is set
// to true, dateDiff returns the difference in number of full years. Otherwise, dateDiff returns the difference in
// number of full months.
func dateDiff(date1, date2 time.Time, yearDiff bool) int64 {
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compare := date1.Compare(date2)
if compare == 0 {
return 0
}
sign := 1
before := date1
after := date2
if compare > 0 {
sign = -1
before = date2
after = date1
}

beforeYear, beforeMonth, beforeDay := before.Date()
afterYear, afterMonth, afterDay := after.Date()

checkDayClock := !yearDiff || afterMonth == beforeMonth
res := int64(afterYear-beforeYear)*12 + int64(afterMonth) - int64(beforeMonth)
if yearDiff {
res = res / 12
}

if checkDayClock {
if beforeDay > afterDay {
res -= 1
} else if beforeDay == afterDay {
beforeHour, beforeMin, beforeSec := before.Clock()
afterHour, afterMin, afterSec := after.Clock()
secondDiff := (afterHour-beforeHour)*3600 + (afterMin-beforeMin)*60 + (afterSec - beforeSec)
if secondDiff < 0 {
res -= 1
} else if secondDiff == 0 && before.Nanosecond() > after.Nanosecond() {
res -= 1
}
}
}

return int64(sign) * res
}
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