add an endpoint for doing SQL selects (#641)

* add an endpoint for doing SQL selects

This adds an endpoint for doing SQL selects directly on a Grist document. Other kinds of statements are not supported. There is a default timeout of a second on queries.

This follows loosely an API design by Alex Hall.

Co-authored-by: jarek <jaroslaw.sadzinski@gmail.com>

app/plugin/DocApiTypes-ti.ts

@@ -84,6 +84,12 @@ export const TablesPatch = t.iface([], {
   "tables": t.tuple("RecordWithStringId", t.rest(t.array("RecordWithStringId"))),
 });
 
+export const SqlPost = t.iface([], {
+  "sql": "string",
+  "args": t.opt(t.array("any")),
+  "timeout": t.opt("number"),
+});
+
 const exportedTypeSuite: t.ITypeSuite = {
   NewRecord,
   NewRecordWithStringId,
@@ -101,5 +107,6 @@ const exportedTypeSuite: t.ITypeSuite = {
   TablePost,
   TablesPost,
   TablesPatch,
+  SqlPost,
 };
 export default exportedTypeSuite;

app/plugin/DocApiTypes.ts

@@ -107,3 +107,16 @@ export interface TablesPost {
 export interface TablesPatch {
   tables: [RecordWithStringId, ...RecordWithStringId[]]; // at least one table is required
 }
+
+/**
+ * JSON schema for the body of api /sql POST endpoint
+ */
+export interface SqlPost {
+  sql: string;
+  args?: any[];      // (It would be nice to support named parameters, but
+                     // that feels tricky currently with node-sqlite3)
+  timeout?: number;  // In msecs. Can only be reduced from server default,
+                     // not increased. Note timeout of a query could affect
+                     // other queued queries on same document, because of
+                     // limitations of API node-sqlite3 exposes.
+}