risingwave_frontend/expr/session_timezone.rs
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// Copyright 2024 RisingWave Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use risingwave_common::types::DataType;
pub use risingwave_pb::expr::expr_node::Type as ExprType;
pub use crate::expr::expr_rewriter::ExprRewriter;
pub use crate::expr::function_call::FunctionCall;
use crate::expr::{Expr, ExprImpl, ExprVisitor};
use crate::session::current;
/// `SessionTimezone` will be used to resolve session
/// timezone-dependent casts, comparisons or arithmetic.
pub struct SessionTimezone {
timezone: String,
/// Whether or not the session timezone was used
used: bool,
}
impl ExprRewriter for SessionTimezone {
fn rewrite_function_call(&mut self, func_call: FunctionCall) -> ExprImpl {
let (func_type, inputs, ret) = func_call.decompose();
let inputs: Vec<ExprImpl> = inputs
.into_iter()
.map(|expr| self.rewrite_expr(expr))
.collect();
if let Some(expr) = self.with_timezone(func_type, &inputs, ret.clone()) {
self.mark_used();
expr
} else {
FunctionCall::new_unchecked(func_type, inputs, ret).into()
}
}
}
impl SessionTimezone {
pub fn new(timezone: String) -> Self {
Self {
timezone,
used: false,
}
}
pub fn timezone(&self) -> String {
self.timezone.clone()
}
pub fn used(&self) -> bool {
self.used
}
fn mark_used(&mut self) {
if !self.used {
self.used = true;
current::notice_to_user(format!(
"Your session timezone is {}. It was used in the interpretation of timestamps and dates in your query. If this is unintended, \
change your timezone to match that of your data's with `set timezone = [timezone]` or \
rewrite your query with an explicit timezone conversion, e.g. with `AT TIME ZONE`.\n",
self.timezone
));
}
}
// Inlines conversions based on session timezone if required by the function
fn with_timezone(
&self,
func_type: ExprType,
inputs: &[ExprImpl],
return_type: DataType,
) -> Option<ExprImpl> {
match func_type {
// `input_timestamptz::varchar`
// => `cast_with_time_zone(input_timestamptz, zone_string)`
// `input_varchar::timestamptz`
// => `cast_with_time_zone(input_varchar, zone_string)`
// `input_date::timestamptz`
// => `input_date::timestamp AT TIME ZONE zone_string`
// `input_timestamp::timestamptz`
// => `input_timestamp AT TIME ZONE zone_string`
// `input_timestamptz::date`
// => `(input_timestamptz AT TIME ZONE zone_string)::date`
// `input_timestamptz::time`
// => `(input_timestamptz AT TIME ZONE zone_string)::time`
// `input_timestamptz::timestamp`
// => `input_timestamptz AT TIME ZONE zone_string`
ExprType::Cast => {
assert_eq!(inputs.len(), 1);
let mut input = inputs[0].clone();
let input_type = input.return_type();
match (input_type, return_type.clone()) {
(DataType::Timestamptz, DataType::Varchar)
| (DataType::Varchar, DataType::Timestamptz) => {
Some(self.cast_with_timezone(input, return_type))
}
(DataType::Date, DataType::Timestamptz)
| (DataType::Timestamp, DataType::Timestamptz) => {
input = input.cast_explicit(DataType::Timestamp).unwrap();
Some(self.at_timezone(input))
}
(DataType::Timestamptz, DataType::Date)
| (DataType::Timestamptz, DataType::Time)
| (DataType::Timestamptz, DataType::Timestamp) => {
input = self.at_timezone(input);
input = input.cast_explicit(return_type).unwrap();
Some(input)
}
_ => None,
}
}
// `lhs_date CMP rhs_timestamptz`
// => `(lhs_date::timestamp AT TIME ZONE zone_string) CMP rhs_timestamptz`
// `lhs_timestamp CMP rhs_timestamptz`
// => `(lhs_timestamp AT TIME ZONE zone_string) CMP rhs_timestamptz`
// `lhs_timestamptz CMP rhs_date`
// => `lhs_timestamptz CMP (rhs_date::timestamp AT TIME ZONE zone_string)`
// `lhs_timestamptz CMP rhs_timestamp`
// => `lhs_timestamptz CMP (rhs_timestamp AT TIME ZONE zone_string)`
ExprType::Equal
| ExprType::NotEqual
| ExprType::LessThan
| ExprType::LessThanOrEqual
| ExprType::GreaterThan
| ExprType::GreaterThanOrEqual
| ExprType::IsDistinctFrom
| ExprType::IsNotDistinctFrom => {
assert_eq!(inputs.len(), 2);
let mut inputs = inputs.to_vec();
for idx in 0..2 {
if matches!(inputs[(idx + 1) % 2].return_type(), DataType::Timestamptz)
&& matches!(
inputs[idx % 2].return_type(),
DataType::Date | DataType::Timestamp
)
{
let mut to_cast = inputs[idx % 2].clone();
// Cast to `Timestamp` first, then use `AT TIME ZONE` to convert to
// `Timestamptz`
to_cast = to_cast.cast_explicit(DataType::Timestamp).unwrap();
inputs[idx % 2] = self.at_timezone(to_cast);
return Some(
FunctionCall::new_unchecked(func_type, inputs, return_type).into(),
);
}
}
None
}
// `add(lhs_interval, rhs_timestamptz)`
// => `add_with_time_zone(rhs_timestamptz, lhs_interval, zone_string)`
// `add(lhs_timestamptz, rhs_interval)`
// => `add_with_time_zone(lhs_timestamptz, rhs_interval, zone_string)`
// `subtract(lhs_timestamptz, rhs_interval)`
// => `subtract_with_time_zone(lhs_timestamptz, rhs_interval, zone_string)`
ExprType::Subtract | ExprType::Add => {
assert_eq!(inputs.len(), 2);
let canonical_match = matches!(inputs[0].return_type(), DataType::Timestamptz)
&& matches!(inputs[1].return_type(), DataType::Interval);
let inverse_match = matches!(inputs[1].return_type(), DataType::Timestamptz)
&& matches!(inputs[0].return_type(), DataType::Interval);
assert!(!(inverse_match && func_type == ExprType::Subtract)); // This should never have been parsed.
if canonical_match || inverse_match {
let (orig_timestamptz, interval) =
if func_type == ExprType::Add && inverse_match {
(inputs[1].clone(), inputs[0].clone())
} else {
(inputs[0].clone(), inputs[1].clone())
};
let new_type = match func_type {
ExprType::Add => ExprType::AddWithTimeZone,
ExprType::Subtract => ExprType::SubtractWithTimeZone,
_ => unreachable!(),
};
let rewritten_expr = FunctionCall::new(
new_type,
vec![
orig_timestamptz,
interval,
ExprImpl::literal_varchar(self.timezone()),
],
)
.unwrap()
.into();
return Some(rewritten_expr);
}
None
}
// `date_trunc(field_string, input_timestamptz)`
// => `date_trunc(field_string, input_timestamptz, zone_string)`
ExprType::DateTrunc | ExprType::Extract | ExprType::DatePart => {
if !(inputs.len() == 2 && inputs[1].return_type() == DataType::Timestamptz) {
return None;
}
assert_eq!(inputs[0].return_type(), DataType::Varchar);
if let ExprImpl::Literal(lit) = &inputs[0]
&& matches!(func_type, ExprType::Extract | ExprType::DatePart)
&& lit
.get_data()
.as_ref()
.map_or(true, |v| v.as_utf8().eq_ignore_ascii_case("epoch"))
{
// No need to rewrite when field is `null` or `epoch`.
// This is optional but avoids false warning in common case.
return None;
}
let mut new_inputs = inputs.to_vec();
new_inputs.push(ExprImpl::literal_varchar(self.timezone()));
Some(FunctionCall::new(func_type, new_inputs).unwrap().into())
}
// `char_to_timestamptz(input_string, format_string)`
// => `char_to_timestamptz(input_string, format_string, zone_string)`
ExprType::CharToTimestamptz => {
if !(inputs.len() == 2
&& inputs[0].return_type() == DataType::Varchar
&& inputs[1].return_type() == DataType::Varchar)
{
return None;
}
let mut new_inputs = inputs.to_vec();
new_inputs.push(ExprImpl::literal_varchar(self.timezone()));
Some(FunctionCall::new(func_type, new_inputs).unwrap().into())
}
// `to_char(input_timestamptz, format_string)`
// => `to_char(input_timestamptz, format_string, zone_string)`
ExprType::ToChar => {
if !(inputs.len() == 2
&& inputs[0].return_type() == DataType::Timestamptz
&& inputs[1].return_type() == DataType::Varchar)
{
return None;
}
let mut new_inputs = inputs.to_vec();
new_inputs.push(ExprImpl::literal_varchar(self.timezone()));
Some(FunctionCall::new(func_type, new_inputs).unwrap().into())
}
_ => None,
}
}
fn at_timezone(&self, input: ExprImpl) -> ExprImpl {
FunctionCall::new(
ExprType::AtTimeZone,
vec![input, ExprImpl::literal_varchar(self.timezone.clone())],
)
.unwrap()
.into()
}
fn cast_with_timezone(&self, input: ExprImpl, return_type: DataType) -> ExprImpl {
FunctionCall::new_unchecked(
ExprType::CastWithTimeZone,
vec![input, ExprImpl::literal_varchar(self.timezone.clone())],
return_type,
)
.into()
}
}
#[derive(Default)]
pub struct TimestamptzExprFinder {
has: bool,
}
impl TimestamptzExprFinder {
pub fn has(&self) -> bool {
self.has
}
}
impl ExprVisitor for TimestamptzExprFinder {
fn visit_function_call(&mut self, func_call: &FunctionCall) {
if func_call.return_type() == DataType::Timestamptz {
self.has = true;
return;
}
for input in &func_call.inputs {
if input.return_type() == DataType::Timestamptz {
self.has = true;
return;
}
}
func_call
.inputs()
.iter()
.for_each(|expr| self.visit_expr(expr));
}
}