risingwave_frontend/optimizer/plan_node/generic/
project.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::collections::{BTreeMap, HashMap};
16use std::fmt;
17
18use fixedbitset::FixedBitSet;
19use itertools::Itertools;
20use pretty_xmlish::{Pretty, StrAssocArr};
21use risingwave_common::catalog::{Field, Schema};
22use risingwave_common::util::iter_util::ZipEqFast;
23
24use super::{GenericPlanNode, GenericPlanRef};
25use crate::expr::{
26    Expr, ExprDisplay, ExprImpl, ExprRewriter, ExprType, ExprVisitor, FunctionCall, InputRef,
27    assert_input_ref,
28};
29use crate::optimizer::optimizer_context::OptimizerContextRef;
30use crate::optimizer::plan_node::StreamPlanRef;
31use crate::optimizer::property::FunctionalDependencySet;
32use crate::utils::{ColIndexMapping, ColIndexMappingRewriteExt};
33
34fn check_expr_type(expr: &ExprImpl) -> std::result::Result<(), &'static str> {
35    if expr.has_subquery() {
36        return Err("subquery");
37    }
38    if expr.has_agg_call() {
39        return Err("aggregate function");
40    }
41    if expr.has_table_function() {
42        return Err("table function");
43    }
44    if expr.has_window_function() {
45        return Err("window function");
46    }
47    Ok(())
48}
49
50/// [`Project`] computes a set of expressions from its input relation.
51#[derive(Debug, Clone, PartialEq, Eq, Hash)]
52#[allow(clippy::manual_non_exhaustive)]
53pub struct Project<PlanRef> {
54    pub exprs: Vec<ExprImpl>,
55    /// Mapping from expr index to field name. May not contain all exprs.
56    pub field_names: BTreeMap<usize, String>,
57    pub input: PlanRef,
58    // we need some check when construct the `Project::new`
59    _private: (),
60}
61
62impl<PlanRef> Project<PlanRef> {
63    pub fn clone_with_input<OtherPlanRef>(&self, input: OtherPlanRef) -> Project<OtherPlanRef> {
64        Project {
65            exprs: self.exprs.clone(),
66            field_names: self.field_names.clone(),
67            input,
68            _private: (),
69        }
70    }
71
72    pub(crate) fn rewrite_exprs(&mut self, r: &mut dyn ExprRewriter) {
73        self.exprs = self
74            .exprs
75            .iter()
76            .map(|e| r.rewrite_expr(e.clone()))
77            .collect();
78    }
79
80    pub(crate) fn visit_exprs(&self, v: &mut dyn ExprVisitor) {
81        self.exprs.iter().for_each(|e| v.visit_expr(e));
82    }
83}
84
85impl<PlanRef: GenericPlanRef> GenericPlanNode for Project<PlanRef> {
86    fn schema(&self) -> Schema {
87        let o2i = self.o2i_col_mapping();
88        let exprs = &self.exprs;
89        let input_schema = self.input.schema();
90        let ctx = self.ctx();
91        let fields = exprs
92            .iter()
93            .enumerate()
94            .map(|(i, expr)| {
95                // Get field info from o2i.
96                let name = match o2i.try_map(i) {
97                    Some(input_idx) => {
98                        if let Some(name) = self.field_names.get(&i) {
99                            name.clone()
100                        } else {
101                            input_schema.fields()[input_idx].name.clone()
102                        }
103                    }
104                    None => match expr {
105                        ExprImpl::InputRef(_) | ExprImpl::Literal(_) => {
106                            format!("{:?}", ExprDisplay { expr, input_schema })
107                        }
108                        _ => {
109                            if let Some(name) = self.field_names.get(&i) {
110                                name.clone()
111                            } else {
112                                format!("$expr{}", ctx.next_expr_display_id())
113                            }
114                        }
115                    },
116                };
117                Field::with_name(expr.return_type(), name)
118            })
119            .collect();
120        Schema { fields }
121    }
122
123    fn stream_key(&self) -> Option<Vec<usize>> {
124        let i2o = self.i2o_col_mapping();
125        self.input
126            .stream_key()?
127            .iter()
128            .map(|pk_col| i2o.try_map(*pk_col))
129            .collect::<Option<Vec<_>>>()
130    }
131
132    fn ctx(&self) -> OptimizerContextRef {
133        self.input.ctx()
134    }
135
136    fn functional_dependency(&self) -> FunctionalDependencySet {
137        let i2o = self.i2o_col_mapping();
138        i2o.rewrite_functional_dependency_set(self.input.functional_dependency().clone())
139    }
140}
141
142impl<PlanRef: GenericPlanRef> Project<PlanRef> {
143    pub fn new(exprs: Vec<ExprImpl>, input: PlanRef) -> Self {
144        for expr in &exprs {
145            assert_input_ref!(expr, input.schema().fields().len());
146            check_expr_type(expr)
147                .map_err(|expr| format!("{expr} should not in Project operator"))
148                .unwrap();
149        }
150        Project {
151            exprs,
152            field_names: Default::default(),
153            input,
154            _private: (),
155        }
156    }
157
158    /// Creates a `Project` which select some columns from the input.
159    ///
160    /// `mapping` should maps from `(0..input_fields.len())` to a consecutive range starting from 0.
161    ///
162    /// This is useful in column pruning when we want to add a project to ensure the output schema
163    /// is correct.
164    pub fn with_mapping(input: PlanRef, mapping: ColIndexMapping) -> Self {
165        if mapping.target_size() == 0 {
166            // The mapping is empty, so the parent actually doesn't need the output of the input.
167            // This can happen when the parent node only selects constant expressions.
168            return Self::new(vec![], input);
169        };
170        let mut input_refs = vec![None; mapping.target_size()];
171        for (src, tar) in mapping.mapping_pairs() {
172            assert_eq!(input_refs[tar], None);
173            input_refs[tar] = Some(src);
174        }
175        let input_schema = input.schema();
176        let exprs: Vec<ExprImpl> = input_refs
177            .into_iter()
178            .map(|i| i.unwrap())
179            .map(|i| InputRef::new(i, input_schema.fields()[i].data_type()).into())
180            .collect();
181
182        Self::new(exprs, input)
183    }
184
185    /// Creates a `Project` which select some columns from the input.
186    pub fn with_out_fields(input: PlanRef, out_fields: &FixedBitSet) -> Self {
187        Self::with_out_col_idx(input, out_fields.ones())
188    }
189
190    pub fn out_col_idx_exprs<'a>(
191        input: &'a PlanRef,
192        out_fields: impl Iterator<Item = usize> + 'a,
193    ) -> impl Iterator<Item = ExprImpl> + 'a {
194        let input_schema = input.schema();
195        out_fields.map(move |index| InputRef::new(index, input_schema[index].data_type()).into())
196    }
197
198    /// Creates a `Project` which select some columns from the input.
199    pub fn with_out_col_idx(input: PlanRef, out_fields: impl Iterator<Item = usize>) -> Self {
200        let exprs = Self::out_col_idx_exprs(&input, out_fields).collect();
201        Self::new(exprs, input)
202    }
203
204    /// Creates a `Project` with an additional `_vnode` column at the end of the schema.
205    pub fn with_vnode_col(input: PlanRef, dist_key: &[usize]) -> Self {
206        let input_fields = input.schema().fields();
207        let mut new_exprs: Vec<_> = input_fields
208            .iter()
209            .enumerate()
210            .map(|(idx, field)| InputRef::new(idx, field.data_type.clone()).into())
211            .collect();
212        new_exprs.push(
213            FunctionCall::new(
214                ExprType::Vnode,
215                dist_key
216                    .iter()
217                    .map(|idx| InputRef::new(*idx, input_fields[*idx].data_type()).into())
218                    .collect(),
219            )
220            .expect("Vnode function call should be valid here")
221            .into(),
222        );
223        let vnode_expr_idx = new_exprs.len() - 1;
224
225        let mut new = Self::new(new_exprs, input);
226        new.field_names.insert(vnode_expr_idx, "_vnode".to_owned());
227        new
228    }
229
230    pub fn decompose(self) -> (Vec<ExprImpl>, PlanRef) {
231        (self.exprs, self.input)
232    }
233
234    pub fn fields_pretty<'a>(&self, schema: &Schema) -> StrAssocArr<'a> {
235        let f = |t| Pretty::debug(&t);
236        let e = Pretty::Array(self.exprs_for_display(schema).iter().map(f).collect());
237        vec![("exprs", e)]
238    }
239
240    fn exprs_for_display<'a>(&'a self, schema: &Schema) -> Vec<AliasedExpr<'a>> {
241        self.exprs
242            .iter()
243            .zip_eq_fast(schema.fields().iter())
244            .map(|(expr, field)| AliasedExpr {
245                expr: ExprDisplay {
246                    expr,
247                    input_schema: self.input.schema(),
248                },
249                alias: {
250                    match expr {
251                        ExprImpl::InputRef(_) | ExprImpl::Literal(_) => None,
252                        _ => Some(field.name.clone()),
253                    }
254                },
255            })
256            .collect()
257    }
258
259    pub fn o2i_col_mapping(&self) -> ColIndexMapping {
260        let exprs = &self.exprs;
261        let input_len = self.input.schema().len();
262        let mut map = vec![None; exprs.len()];
263        for (i, expr) in exprs.iter().enumerate() {
264            if let ExprImpl::InputRef(input) = expr {
265                map[i] = Some(input.index())
266            }
267        }
268        ColIndexMapping::new(map, input_len)
269    }
270
271    /// get the Mapping of columnIndex from input column index to output column index,if a input
272    /// column corresponds more than one out columns, mapping to any one
273    pub fn i2o_col_mapping(&self) -> ColIndexMapping {
274        let exprs = &self.exprs;
275        let input_len = self.input.schema().len();
276        let mut map = vec![None; input_len];
277        for (i, expr) in exprs.iter().enumerate() {
278            if let ExprImpl::InputRef(input) = expr {
279                map[input.index()] = Some(i)
280            }
281        }
282        ColIndexMapping::new(map, exprs.len())
283    }
284
285    pub fn is_all_inputref(&self) -> bool {
286        self.exprs
287            .iter()
288            .all(|expr| matches!(expr, ExprImpl::InputRef(_)))
289    }
290
291    pub fn is_identity(&self) -> bool {
292        self.exprs.len() == self.input.schema().len()
293        && self
294            .exprs
295            .iter()
296            .zip_eq_fast(self.input.schema().fields())
297            .enumerate()
298            .all(|(i, (expr, field))| {
299                matches!(expr, ExprImpl::InputRef(input_ref) if **input_ref == InputRef::new(i, field.data_type()))
300            })
301    }
302
303    pub fn try_as_projection(&self) -> Option<Vec<usize>> {
304        self.exprs
305            .iter()
306            .map(|expr| match expr {
307                ExprImpl::InputRef(input_ref) => Some(input_ref.index),
308                _ => None,
309            })
310            .collect::<Option<Vec<_>>>()
311    }
312}
313
314impl Project<StreamPlanRef> {
315    /// Returns whether the `Project` is likely to produce noop updates. If so, the executor will
316    /// eliminate them to avoid emitting unnecessary changes.
317    pub(crate) fn likely_produces_noop_updates(&self) -> bool {
318        // 1. `NOW()` is often truncated to a granularity such as day, week, or month, which
319        //    seldom changes. Eliminate noop updates can reduce unnecessary changes.
320        if self.input.as_stream_now().is_some() {
321            return true;
322        }
323
324        // 2. If the `Project` contains jsonb access, it's very likely that the query is extracting
325        //    some fields from a jsonb payload column. In this case, a change from the input jsonb
326        //    payload may not change the output of the `Project`.
327        struct HasJsonbAccess {
328            has: bool,
329        }
330
331        impl ExprVisitor for HasJsonbAccess {
332            fn visit_function_call(&mut self, func_call: &FunctionCall) {
333                if matches!(
334                    func_call.func_type(),
335                    ExprType::JsonbAccess
336                        | ExprType::JsonbAccessStr
337                        | ExprType::JsonbExtractPath
338                        | ExprType::JsonbExtractPathVariadic
339                        | ExprType::JsonbExtractPathText
340                        | ExprType::JsonbExtractPathTextVariadic
341                        | ExprType::JsonbPathExists
342                        | ExprType::JsonbPathMatch
343                        | ExprType::JsonbPathQueryArray
344                        | ExprType::JsonbPathQueryFirst
345                ) {
346                    self.has = true;
347                }
348            }
349        }
350
351        self.exprs.iter().any(|expr| {
352            // When there's a jsonb access in the `Project`, it's very likely that the query is
353            // extracting some fields from a jsonb payload column. In this case, a change from the
354            // input jsonb payload may not change the output of the `Project`.
355            let mut visitor = HasJsonbAccess { has: false };
356            visitor.visit_expr(expr);
357            visitor.has
358        })
359    }
360}
361
362/// Construct a `Project` and dedup expressions.
363/// expressions
364#[derive(Default)]
365pub struct ProjectBuilder {
366    exprs: Vec<ExprImpl>,
367    exprs_index: HashMap<ExprImpl, usize>,
368}
369
370impl ProjectBuilder {
371    /// add an expression to the `LogicalProject` and return the column index of the project's
372    /// output
373    pub fn add_expr(&mut self, expr: &ExprImpl) -> std::result::Result<usize, &'static str> {
374        check_expr_type(expr)?;
375        if let Some(idx) = self.exprs_index.get(expr) {
376            Ok(*idx)
377        } else {
378            let index = self.exprs.len();
379            self.exprs.push(expr.clone());
380            self.exprs_index.insert(expr.clone(), index);
381            Ok(index)
382        }
383    }
384
385    pub fn get_expr(&self, index: usize) -> Option<&ExprImpl> {
386        self.exprs.get(index)
387    }
388
389    pub fn expr_index(&self, expr: &ExprImpl) -> Option<usize> {
390        check_expr_type(expr).ok()?;
391        self.exprs_index.get(expr).copied()
392    }
393
394    /// build the `LogicalProject` from `LogicalProjectBuilder`
395    pub fn build<PlanRef: GenericPlanRef>(self, input: PlanRef) -> Project<PlanRef> {
396        Project::new(self.exprs, input)
397    }
398
399    pub fn exprs_len(&self) -> usize {
400        self.exprs.len()
401    }
402}
403
404/// Auxiliary struct for displaying `expr AS alias`
405pub struct AliasedExpr<'a> {
406    pub expr: ExprDisplay<'a>,
407    pub alias: Option<String>,
408}
409
410impl fmt::Debug for AliasedExpr<'_> {
411    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
412        match &self.alias {
413            Some(alias) => write!(f, "{:?} as {}", self.expr, alias),
414            None => write!(f, "{:?}", self.expr),
415        }
416    }
417}
418
419/// Given the index of required cols, return a vec of permutation index, so that after we sort the `required_cols`,
420/// and re-apply with a projection with the permutation index, we can restore the original `required_cols`.
421///
422/// For example, when the `required_cols` is `[5, 3, 10]`, the `sorted_required_cols` is `[3, 5, 10]`, and the permutation index is
423/// `[1, 0, 2]`, so that `[sorted_required_cols[1], sorted_required_cols[0], sorted_required_cols[2]]` equals the original `[5, 3, 10]`
424pub fn ensure_sorted_required_cols(
425    required_cols: &[usize],
426    schema: &Schema,
427) -> (Vec<ExprImpl>, Vec<usize>) {
428    let mut required_cols_with_output_idx = required_cols.iter().copied().enumerate().collect_vec();
429    required_cols_with_output_idx.sort_by_key(|(_, col_idx)| *col_idx);
430    let mut output_indices = vec![0; required_cols.len()];
431    let mut sorted_col_idx = Vec::with_capacity(required_cols.len());
432
433    for (sorted_input_idx, (output_idx, col_idx)) in
434        required_cols_with_output_idx.into_iter().enumerate()
435    {
436        sorted_col_idx.push(col_idx);
437        output_indices[output_idx] = sorted_input_idx;
438    }
439
440    (
441        output_indices
442            .into_iter()
443            .map(|sorted_input_idx| {
444                InputRef::new(
445                    sorted_input_idx,
446                    schema[sorted_col_idx[sorted_input_idx]].data_type(),
447                )
448                .into()
449            })
450            .collect(),
451        sorted_col_idx,
452    )
453}
454
455#[cfg(test)]
456mod tests {
457
458    use itertools::Itertools;
459    use rand::prelude::SliceRandom;
460    use rand::rng;
461    use risingwave_common::catalog::{Field, Schema};
462    use risingwave_common::types::DataType;
463
464    use super::ensure_sorted_required_cols;
465
466    #[test]
467    fn test_ensure_sorted_required_cols() {
468        let input_len = 10;
469        let schema = Schema::new(
470            (0..input_len)
471                .map(|_| Field::unnamed(DataType::Int32))
472                .collect(),
473        );
474        let mut required_cols = (0..input_len)
475            .filter(|_| rand::random_bool(0.5))
476            .collect_vec();
477        let sorted_required_cols = required_cols.clone();
478        required_cols.shuffle(&mut rng());
479        let required_cols = required_cols;
480
481        let (output_exprs, sorted) = ensure_sorted_required_cols(&required_cols, &schema);
482        assert_eq!(sorted, sorted_required_cols);
483        assert_eq!(
484            output_exprs
485                .iter()
486                .map(|expr| sorted_required_cols[expr.as_input_ref().unwrap().index])
487                .collect_vec(),
488            required_cols
489        );
490    }
491}
risingwave_frontend/optimizer/plan_node/generic/project.rs

risingwave_frontend/optimizer/plan_node/generic/
project.rs
