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feat: derive monotonicity for date_truc with timezone when unit larger than day #20097

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feat: derive monotonicity for date_truc with timezone when unit larger than day #20097

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feat: derive monotonicity for date_truc with timezone when unit large…
st1page Jan 10, 2025
c06b0c6
typo
st1page Jan 10, 2025
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1 change: 1 addition & 0 deletions src/expr/impl/src/scalar/date_trunc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ const MILLENNIUM: &str = "millennium";

#[function("date_trunc(varchar, timestamp) -> timestamp")]
pub fn date_trunc_timestamp(field: &str, ts: Timestamp) -> Result<Timestamp> {
// NOTE(st1page): please also modify the `MonotonicityAnalyzer::date_unit_larger_than_day` in frontend if this changes
Ok(match field.to_ascii_lowercase().as_str() {
MICROSECONDS => ts.truncate_micros(),
MILLISECONDS => ts.truncate_millis(),
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6 changes: 6 additions & 0 deletions src/frontend/planner_test/tests/testdata/input/temporal_filter.yaml
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Expand Up @@ -123,6 +123,12 @@
select * from t where ts + interval '1 hour' > date_trunc('day', now());
expected_outputs:
- stream_plan
- name: date_truc_with_timezone
sql: |
create table t (ts timestamp with time zone, a int);
select * from t where ts + interval '1 hour' > date_trunc('day', now(), 'Asia/Singapore');
expected_outputs:
- stream_plan
- name: Non-trivial now expression 2
sql: |
create table t (ts timestamp with time zone, a int);
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13 changes: 13 additions & 0 deletions src/frontend/planner_test/tests/testdata/output/temporal_filter.yaml
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Expand Up @@ -476,6 +476,19 @@
└─StreamExchange { dist: Broadcast }
└─StreamProject { exprs: [DateTrunc('day':Varchar, now, 'UTC':Varchar) as $expr2], output_watermarks: [$expr2] }
└─StreamNow { output: [now] }
- name: date_truc_with_timezone
sql: |
create table t (ts timestamp with time zone, a int);
select * from t where ts + interval '1 hour' > date_trunc('day', now(), 'Asia/Singapore');
stream_plan: |-
StreamMaterialize { columns: [ts, a, t._row_id(hidden)], stream_key: [t._row_id], pk_columns: [t._row_id], pk_conflict: NoCheck }
└─StreamProject { exprs: [t.ts, t.a, t._row_id] }
└─StreamDynamicFilter { predicate: ($expr1 > $expr2), output_watermarks: [$expr1], output: [t.ts, t.a, $expr1, t._row_id], cleaned_by_watermark: true }
├─StreamProject { exprs: [t.ts, t.a, AddWithTimeZone(t.ts, '01:00:00':Interval, 'UTC':Varchar) as $expr1, t._row_id] }
│ └─StreamTableScan { table: t, columns: [t.ts, t.a, t._row_id], stream_scan_type: ArrangementBackfill, stream_key: [t._row_id], pk: [_row_id], dist: UpstreamHashShard(t._row_id) }
└─StreamExchange { dist: Broadcast }
└─StreamProject { exprs: [DateTrunc('day':Varchar, now, 'Asia/Singapore':Varchar) as $expr2], output_watermarks: [$expr2] }
└─StreamNow { output: [now] }
- name: Non-trivial now expression 2
sql: |
create table t (ts timestamp with time zone, a int);
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25 changes: 24 additions & 1 deletion src/frontend/src/optimizer/property/monotonicity.rs
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Expand Up @@ -186,6 +186,23 @@ impl MonotonicityAnalyzer {
tz_is_utc // conservative
}

fn date_unit_larger_than_day(date_unit: Option<&str>) -> bool {
const DAY: &str = "day";
const WEEK: &str = "week";
const MONTH: &str = "month";
const QUARTER: &str = "quarter";
const YEAR: &str = "year";
const DECADE: &str = "decade";
const CENTURY: &str = "century";
const MILLENNIUM: &str = "millennium";
date_unit.map_or(false, |date_unit| {
matches!(
date_unit.to_ascii_lowercase().as_str(),
DAY | WEEK | MONTH | QUARTER | YEAR | DECADE | CENTURY | MILLENNIUM
)
})
Comment on lines +190 to +203
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what's the point of the const here

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In case SQL is standardized to use a language other than English in the future?

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just maintain it same as the expression's implementation

risingwave/src/expr/impl/src/scalar/date_trunc.rs

Lines 20 to 33 in c06b0c6

// TODO(xiangjinwu): parse into an enum
const MICROSECONDS: &str = "microseconds";
const MILLISECONDS: &str = "milliseconds";
const SECOND: &str = "second";
const MINUTE: &str = "minute";
const HOUR: &str = "hour";
const DAY: &str = "day";
const WEEK: &str = "week";
const MONTH: &str = "month";
const QUARTER: &str = "quarter";
const YEAR: &str = "year";
const DECADE: &str = "decade";
const CENTURY: &str = "century";
const MILLENNIUM: &str = "millennium";

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I mean why not use those existing definition?

It doesn't make sense to

  • Define const repeatedly in multiple places
  • Define const in-place just before its usage site

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This modification is a bit troublesome; we have to expose these const from a very deep level within expr... Since we might never modify it, I would rather make a copy.

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You could move these const from the deep mod into a upper layer, and import it in the original place. That should be easy to do.

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I am too lazy....

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Your brain will become rusty!

}

match func_call.func_type() {
ExprType::Unspecified => unreachable!(),
ExprType::Add => match self.visit_binary_op(func_call.inputs()) {
Expand Down Expand Up @@ -257,7 +274,13 @@ impl MonotonicityAnalyzer {
.as_literal()
.and_then(|literal| literal.get_data().as_ref())
.map(|tz| tz.as_utf8().as_ref());
if time_zone_is_without_dst(time_zone) {
let date_unit = func_call.inputs()[0]
.as_literal()
.and_then(|literal| literal.get_data().as_ref())
.map(|tz| tz.as_utf8().as_ref());
if time_zone_is_without_dst(time_zone)
|| date_unit_larger_than_day(date_unit)
{
Comment on lines +277 to +283
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Can you please add an example to demonstrate the correctness?

What I can think of is like in a timezone with DST, MM-dd 23:50:00 + interval 12 minutes may be MM-dd 23:02:00, while the date_trunc('day', ...) result be MM-dd 00:12:00 versus MM-dd (00:00:00). Seems this will break the correctness. Am I understanding it wrong?

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@xxchan xxchan Jan 20, 2025 •
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it has all fields that are less significant than the selected one set to zero (or one, for day and month).
https://arc.net/l/quote/wfxyyukb

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it has all fields that are less significant than the selected one set to zero (or one, for day and month).

Yes I know that.

I just got it. In my previous comment, I mixed F(X + C) with F(X) + C. I think what we need to ensure here is that, if X2 > X1, F(X2) > F(X1), and vice versa. We don't need to compare F(X + C) with F(X) + C.

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@xiangjinwu xiangjinwu Jan 20, 2025 •
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related: #13201
In short:

  • PostgreSQL does treat units >= day and units < day differently (redotz boolean flag)
  • Counter-intuitively, it is possible that date_trunc('day', x) > x and the return value has hour != 0

There may be more tricky cases to think about carefully.

I think what we need to ensure here is that, if X2 > X1, F(X2) > F(X1), and vice versa.

  • We only have X2 > X1 implies F(X2) >= F(X1) with the equal sign
  • Do you mean F(X2) > F(X1) implies X2 > X1 by vice versa?

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  • We only have X2 > X1 implies F(X2) >= F(X1) with the equal sign
  • Do you mean F(X2) > F(X1) implies X2 > X1 by vice versa?

Yes. Thank for the equal sign though. To be clear, I think it should be:

  • X2 >= X1 → F(X2) >= F(X1)
  • F(X2) >= F(X1) → X2 >= X1
  • X2 <= X1 → F(X2) <= F(X1)
  • F(X2) <= F(X1) → X2 <= X1

Only with the four all satisfied, we can say F maintains the monotonicity.

any
} else {
Inherent(Unknown)
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