dbx_core/sql/optimizer/
projection_pushdown.rs

1//! Rule 2: Projection Pushdown
2//!
3//! 불필요한 컬럼을 조기 제거하여 메모리 절감
4
5use crate::error::DbxResult;
6use crate::sql::planner::{Expr, LogicalPlan};
7
8use super::OptimizationRule;
9
10/// 불필요한 컬럼을 조기 제거하여 메모리 절감
11pub struct ProjectionPushdownRule;
12
13impl OptimizationRule for ProjectionPushdownRule {
14    fn name(&self) -> &str {
15        "ProjectionPushdown"
16    }
17
18    fn apply(&self, plan: LogicalPlan) -> DbxResult<LogicalPlan> {
19        self.push_down(plan)
20    }
21}
22
23impl ProjectionPushdownRule {
24    fn push_down(&self, plan: LogicalPlan) -> DbxResult<LogicalPlan> {
25        match plan {
26            LogicalPlan::Project {
27                input,
28                projections: columns,
29            } => {
30                let optimized_input = self.push_down(*input)?;
31                match optimized_input {
32                    LogicalPlan::Scan {
33                        table,
34                        columns: scan_cols,
35                        filter,
36                        ros_files,
37                    } if !columns.is_empty() => {
38                        let needed = self.extract_column_names(&columns);
39                        let final_cols = if scan_cols.is_empty() {
40                            needed
41                        } else {
42                            scan_cols
43                                .into_iter()
44                                .filter(|c| needed.contains(c))
45                                .collect()
46                        };
47                        Ok(LogicalPlan::Project {
48                            input: Box::new(LogicalPlan::Scan {
49                                table,
50                                columns: final_cols,
51                                filter,
52                                ros_files,
53                            }),
54                            projections: columns,
55                        })
56                    }
57                    other => Ok(LogicalPlan::Project {
58                        input: Box::new(other),
59                        projections: columns,
60                    }),
61                }
62            }
63            LogicalPlan::Filter { input, predicate } => Ok(LogicalPlan::Filter {
64                input: Box::new(self.push_down(*input)?),
65                predicate,
66            }),
67            LogicalPlan::Sort { input, order_by } => Ok(LogicalPlan::Sort {
68                input: Box::new(self.push_down(*input)?),
69                order_by,
70            }),
71            LogicalPlan::Limit {
72                input,
73                count,
74                offset,
75            } => Ok(LogicalPlan::Limit {
76                input: Box::new(self.push_down(*input)?),
77                count,
78                offset,
79            }),
80            LogicalPlan::Aggregate {
81                input,
82                group_by,
83                aggregates,
84                mode,
85            } => Ok(LogicalPlan::Aggregate {
86                input: Box::new(self.push_down(*input)?),
87                group_by,
88                aggregates,
89                mode,
90            }),
91            other => Ok(other),
92        }
93    }
94
95    /// Extract column names referenced in expressions.
96    fn extract_column_names(&self, projections: &[(Expr, Option<String>)]) -> Vec<String> {
97        let mut names = Vec::new();
98        for (expr, _) in projections {
99            self.collect_columns(expr, &mut names);
100        }
101        names.sort();
102        names.dedup();
103        names
104    }
105
106    fn collect_columns(&self, expr: &Expr, out: &mut Vec<String>) {
107        match expr {
108            Expr::Column(name) => out.push(name.clone()),
109            Expr::BinaryOp { left, right, .. } => {
110                self.collect_columns(left, out);
111                self.collect_columns(right, out);
112            }
113            Expr::Function { args, .. } => {
114                for arg in args {
115                    self.collect_columns(arg, out);
116                }
117            }
118            Expr::IsNull(inner) | Expr::IsNotNull(inner) => {
119                self.collect_columns(inner, out);
120            }
121            Expr::InList { expr, list, .. } => {
122                self.collect_columns(expr, out);
123                for item in list {
124                    self.collect_columns(item, out);
125                }
126            }
127            _ => {}
128        }
129    }
130}
dbx_core/sql/optimizer/projection_pushdown.rs

dbx_core/sql/optimizer/
projection_pushdown.rs
