llkv_plan/
table_scan.rs

1use arrow::datatypes::DataType;
2
3use llkv_expr::{Expr, ScalarExpr};
4use llkv_types::{FieldId, LogicalFieldId, TableId};
5
6use crate::{
7    PlanEdge, PlanExpression, PlanField, PlanGraph, PlanGraphBuilder, PlanGraphError, PlanNode,
8    PlanNodeId, PlanOperator,
9};
10
11/// Projection descriptor for building table-scan plan graphs without depending
12/// on storage-specific types.
13pub enum TableScanProjectionSpec {
14    Column {
15        logical_field_id: LogicalFieldId,
16        data_type: DataType,
17        alias: Option<String>,
18    },
19    Computed {
20        expr: ScalarExpr<FieldId>,
21        alias: String,
22        data_type: DataType,
23    },
24}
25
26/// Build a `PlanGraph` for a table scan with optional filter and projections.
27///
28/// This mirrors the graph previously assembled inside `llkv-table` so EXPLAIN
29/// output remains stable while allowing the planner to live in `llkv-plan`.
30pub fn build_table_scan_plan(
31    table_id: TableId,
32    projections: &[TableScanProjectionSpec],
33    filter_expr: &Expr<'_, FieldId>,
34    include_nulls: bool,
35) -> Result<PlanGraph, PlanGraphError> {
36    let mut builder = PlanGraphBuilder::new();
37
38    let scan_node_id = PlanNodeId::new(1);
39    let mut scan_node = PlanNode::new(scan_node_id, PlanOperator::TableScan);
40    scan_node.metadata.insert("table_id", table_id.to_string());
41    scan_node
42        .metadata
43        .insert("projection_count", projections.len().to_string());
44    builder.add_node(scan_node)?;
45    builder.add_root(scan_node_id)?;
46
47    let mut next_node = 2u32;
48    let mut parent = scan_node_id;
49
50    if !filter_expr.is_trivially_true() {
51        let filter_node_id = PlanNodeId::new(next_node);
52        next_node += 1;
53        let mut filter_node = PlanNode::new(filter_node_id, PlanOperator::Filter);
54        filter_node.add_predicate(PlanExpression::new(filter_expr.format_display()));
55        builder.add_node(filter_node)?;
56        builder.add_edge(PlanEdge::new(parent, filter_node_id))?;
57        parent = filter_node_id;
58    }
59
60    let project_node_id = PlanNodeId::new(next_node);
61    next_node += 1;
62    let mut project_node = PlanNode::new(project_node_id, PlanOperator::Project);
63
64    for projection in projections {
65        match projection {
66            TableScanProjectionSpec::Column {
67                logical_field_id,
68                data_type,
69                alias,
70            } => {
71                let fallback = logical_field_id.field_id().to_string();
72                let name = alias.clone().unwrap_or(fallback);
73                project_node.add_projection(PlanExpression::new(format!("column({name})")));
74                project_node.add_field(
75                    PlanField::new(name, format!("{data_type:?}")).with_nullability(true),
76                );
77            }
78            TableScanProjectionSpec::Computed {
79                expr,
80                alias,
81                data_type,
82            } => {
83                project_node.add_projection(PlanExpression::new(format!(
84                    "{} := {}",
85                    alias,
86                    expr.format_display()
87                )));
88                project_node.add_field(
89                    PlanField::new(alias.clone(), format!("{data_type:?}")).with_nullability(true),
90                );
91            }
92        }
93    }
94
95    builder.add_node(project_node)?;
96    builder.add_edge(PlanEdge::new(parent, project_node_id))?;
97    parent = project_node_id;
98
99    let output_node_id = PlanNodeId::new(next_node);
100    let mut output_node = PlanNode::new(output_node_id, PlanOperator::Output);
101    output_node
102        .metadata
103        .insert("include_nulls", include_nulls.to_string());
104    builder.add_node(output_node)?;
105    builder.add_edge(PlanEdge::new(parent, output_node_id))?;
106
107    let annotations = builder.annotations_mut();
108    annotations.description = Some("table.scan_stream".to_string());
109    annotations
110        .properties
111        .insert("table_id".to_string(), table_id.to_string());
112
113    builder.finish()
114}
llkv_plan/table_scan.rs

llkv_plan/
table_scan.rs
