dbmcp_postgres/tools/
list_views.rs

1//! MCP tool: `listViews`.
2
3use std::borrow::Cow;
4
5use dbmcp_server::pagination::{Cursor, Pager};
6use dbmcp_sql::Connection as _;
7use rmcp::handler::server::router::tool::{AsyncTool, ToolBase};
8use rmcp::model::{ErrorData, ToolAnnotations};
9
10use crate::PostgresHandler;
11use crate::types::{ListViewsResponse, PinnedListViewsRequest, UnpinnedListViewsRequest};
12
13const NAME: &str = "listViews";
14const TITLE: &str = "List Views";
15const DESCRIPTION_PINNED: &str = include_str!("../../assets/tools/list_views/pinned.md");
16const DESCRIPTION_UNPINNED: &str = include_str!("../../assets/tools/list_views/unpinned.md");
17
18fn annotations() -> ToolAnnotations {
19    ToolAnnotations::new()
20        .read_only(true)
21        .destructive(false)
22        .idempotent(true)
23        .open_world(false)
24}
25
26/// Marker type for the `listViews` MCP tool (pinned variant — no `database` field).
27pub(crate) struct PinnedListViewsTool;
28
29impl ToolBase for PinnedListViewsTool {
30    type Parameter = PinnedListViewsRequest;
31    type Output = ListViewsResponse;
32    type Error = ErrorData;
33
34    fn name() -> Cow<'static, str> {
35        NAME.into()
36    }
37
38    fn title() -> Option<String> {
39        Some(TITLE.into())
40    }
41
42    fn description() -> Option<Cow<'static, str>> {
43        Some(DESCRIPTION_PINNED.into())
44    }
45
46    fn annotations() -> Option<ToolAnnotations> {
47        Some(annotations())
48    }
49}
50
51impl AsyncTool<PostgresHandler> for PinnedListViewsTool {
52    async fn invoke(handler: &PostgresHandler, params: Self::Parameter) -> Result<Self::Output, Self::Error> {
53        handler
54            .list_views(None, params.cursor, params.search, params.detailed)
55            .await
56    }
57}
58
59/// Marker type for the `listViews` MCP tool (unpinned variant — carries `database`).
60pub(crate) struct UnpinnedListViewsTool;
61
62impl ToolBase for UnpinnedListViewsTool {
63    type Parameter = UnpinnedListViewsRequest;
64    type Output = ListViewsResponse;
65    type Error = ErrorData;
66
67    fn name() -> Cow<'static, str> {
68        NAME.into()
69    }
70
71    fn title() -> Option<String> {
72        Some(TITLE.into())
73    }
74
75    fn description() -> Option<Cow<'static, str>> {
76        Some(DESCRIPTION_UNPINNED.into())
77    }
78
79    fn annotations() -> Option<ToolAnnotations> {
80        Some(annotations())
81    }
82}
83
84impl AsyncTool<PostgresHandler> for UnpinnedListViewsTool {
85    async fn invoke(handler: &PostgresHandler, params: Self::Parameter) -> Result<Self::Output, Self::Error> {
86        handler
87            .list_views(
88                params.database,
89                params.inner.cursor,
90                params.inner.search,
91                params.inner.detailed,
92            )
93            .await
94    }
95}
96
97/// Brief-mode SQL: `pg_views` scan with `ILIKE` filter on view name.
98///
99/// `pg_views` already excludes materialized views (those live in `pg_matviews`),
100/// and `schemaname = 'public'` keeps system-schema views out. The
101/// `($1::text IS NULL OR ...)` trinary lets one statement cover both filtered
102/// and unfiltered cases. View names are unique per schema (Postgres enforces
103/// this), so `viewname` alone is a stable sort key — no tiebreaker needed.
104const BRIEF_SQL: &str = r"
105    SELECT viewname
106    FROM pg_views
107    WHERE schemaname = 'public'
108      AND ($1::text IS NULL OR viewname ILIKE '%' || $1 || '%')
109    ORDER BY viewname
110    LIMIT $2 OFFSET $3";
111
112/// Detailed-mode SQL: per-view `json_build_object` projection.
113///
114/// `pg_views` excludes materialized views. The `pg_namespace` + `pg_class`
115/// joins anchor the relation OID needed by `obj_description`. Postgres defers
116/// SELECT-list evaluation past `LIMIT`, so `obj_description` only runs for the
117/// page's rows — never the full schema. `pg_views.viewowner` is already a role
118/// name, so no `pg_roles` join is needed. View names are unique per schema, so
119/// `viewname` alone is a stable sort key.
120const DETAILED_SQL: &str = r"
121    SELECT
122        v.viewname AS name,
123        json_build_object(
124            'schema',      v.schemaname,
125            'owner',       v.viewowner,
126            'description', pg_catalog.obj_description(c.oid, 'pg_class'),
127            'definition',  v.definition
128        ) AS entry
129    FROM pg_views v
130    JOIN pg_namespace n ON n.nspname = v.schemaname
131    JOIN pg_class     c ON c.relname = v.viewname AND c.relnamespace = n.oid
132    WHERE v.schemaname = 'public'
133      AND ($1::text IS NULL OR v.viewname ILIKE '%' || $1 || '%')
134    ORDER BY v.viewname
135    LIMIT $2 OFFSET $3";
136
137impl PostgresHandler {
138    /// Lists one page of user-defined views, optionally filtered and/or detailed.
139    ///
140    /// # Errors
141    ///
142    /// Returns [`ErrorData`] with code `-32602` if `cursor` is malformed,
143    /// or an internal-error [`ErrorData`] if `database` is invalid
144    /// or the underlying query fails.
145    pub async fn list_views(
146        &self,
147        database: Option<String>,
148        cursor: Option<Cursor>,
149        search: Option<String>,
150        detailed: bool,
151    ) -> Result<ListViewsResponse, ErrorData> {
152        let database = database.as_deref().map(str::trim).filter(|s| !s.is_empty());
153        let pattern = search.as_deref().map(str::trim).filter(|s| !s.is_empty());
154        let pager = Pager::new(cursor, self.config.page_size);
155
156        if detailed {
157            let rows: Vec<(String, sqlx::types::Json<serde_json::Value>)> = self
158                .connection
159                .fetch(
160                    sqlx::query(DETAILED_SQL)
161                        .bind(pattern)
162                        .bind(pager.limit())
163                        .bind(pager.offset()),
164                    database,
165                )
166                .await?;
167            let (rows, next_cursor) = pager.paginate(rows);
168            return Ok(ListViewsResponse::detailed(
169                rows.into_iter().map(|(key, json)| (key, json.0)).collect(),
170                next_cursor,
171            ));
172        }
173
174        let rows: Vec<String> = self
175            .connection
176            .fetch_scalar(
177                sqlx::query(BRIEF_SQL)
178                    .bind(pattern)
179                    .bind(pager.limit())
180                    .bind(pager.offset()),
181                database,
182            )
183            .await?;
184        let (views, next_cursor) = pager.paginate(rows);
185        Ok(ListViewsResponse::brief(views, next_cursor))
186    }
187}
dbmcp_postgres/tools/list_views.rs

dbmcp_postgres/tools/
list_views.rs
