dbmcp_sqlite/tools/
explain_query.rs

1//! MCP tool: `explainQuery`.
2
3use dbmcp_pii::MaybeRedact as _;
4use dbmcp_server::types::QueryResponse;
5use dbmcp_sql::validation::validate_single_statement;
6
7use super::prelude::*;
8use crate::types::ExplainQueryRequest;
9
10const NAME: &str = "explainQuery";
11const TITLE: &str = "Explain Query";
12const DESCRIPTION: &str = include_str!("../../assets/tools/explain_query.md");
13
14/// Marker type for the `explainQuery` MCP tool.
15pub(crate) struct ExplainQueryTool;
16
17impl ToolBase for ExplainQueryTool {
18    type Parameter = ExplainQueryRequest;
19    type Output = QueryResponse;
20    type Error = ErrorData;
21
22    fn name() -> Cow<'static, str> {
23        NAME.into()
24    }
25
26    fn title() -> Option<String> {
27        Some(TITLE.into())
28    }
29
30    fn description() -> Option<Cow<'static, str>> {
31        Some(DESCRIPTION.into())
32    }
33
34    fn annotations() -> Option<ToolAnnotations> {
35        Some(
36            ToolAnnotations::new()
37                .read_only(true)
38                .destructive(false)
39                .idempotent(true)
40                .open_world(true),
41        )
42    }
43
44    fn input_schema() -> Option<Arc<JsonObject>> {
45        Some(input_schema::<Self::Parameter>(true))
46    }
47
48    fn output_schema() -> Option<Arc<JsonObject>> {
49        Some(output_schema::<Self::Output>())
50    }
51}
52
53impl AsyncTool<SqliteHandler> for ExplainQueryTool {
54    async fn invoke(handler: &SqliteHandler, params: Self::Parameter) -> Result<Self::Output, Self::Error> {
55        handler.explain_query(params).await
56    }
57}
58
59impl SqliteHandler {
60    /// Returns the execution plan for a query.
61    ///
62    /// Always uses `EXPLAIN QUERY PLAN` — `SQLite` does not support
63    /// `EXPLAIN ANALYZE`.
64    ///
65    /// # Errors
66    ///
67    /// Returns [`SqlError::MultiStatement`] if the query holds more than
68    /// one statement.
69    /// Returns [`SqlError::Query`] if the backend reports an error.
70    pub async fn explain_query(
71        &self,
72        ExplainQueryRequest { query }: ExplainQueryRequest,
73    ) -> Result<QueryResponse, ErrorData> {
74        validate_single_statement(&query, &sqlparser::dialect::SQLiteDialect {})?;
75
76        let explain_sql = format!("EXPLAIN QUERY PLAN {query}");
77
78        let rows = self.connection.fetch_json(explain_sql.as_str(), None).await?;
79        let rows = self.redactor.redact_rows(rows).await?;
80
81        Ok(QueryResponse { rows })
82    }
83}
dbmcp_sqlite/tools/explain_query.rs

dbmcp_sqlite/tools/
explain_query.rs
