From 4e6626f27e3dbfb908b5d9b64ce25dfb007947f7 Mon Sep 17 00:00:00 2001
From: mogbonjubolaolasunkanmi-art <mogbonjubolaolasunkanmi@gmail.com>
Date: Mon, 22 Jun 2026 08:42:52 +0000
Subject: [PATCH] fix(gists): dynamic radius with ST_DWithin, distance in
 response (#607)

- Add GIST spatial index on location::geography for query performance
- Add ::geography cast to ST_DWithin and ST_Distance in findNearby()
- Add expires_at > NOW() filter to findNearby()
- Sort results by distance_meters ASC, created_at DESC
- Map distance_meters -> distanceMeters on each returned Gist
- Add distanceMeters optional field to Gist entity type
- Fix duplicate import and unreachable code in gists.service.ts

Closes #607
---
 Backend/src/gists/entities/gist.entity.ts |  4 ++++
 Backend/src/gists/gist.repository.ts      | 14 ++++++++++----
 Backend/src/gists/gists.service.ts        | 13 +------------
 3 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/Backend/src/gists/entities/gist.entity.ts b/Backend/src/gists/entities/gist.entity.ts
index 8eae7db4..6a27fc8b 100644
--- a/Backend/src/gists/entities/gist.entity.ts
+++ b/Backend/src/gists/entities/gist.entity.ts
@@ -3,6 +3,7 @@ import { Entity, PrimaryGeneratedColumn, Column, CreateDateColumn, Index } from
 @Entity('gists')
 @Index('idx_gists_location_cell')
 @Index('idx_gists_author_address')
+@Index('idx_gists_location_geography', { synchronize: false })
 export class Gist {
   @PrimaryGeneratedColumn('uuid')
   id: string;
@@ -36,4 +37,7 @@ export class Gist {
 
   @CreateDateColumn({ type: 'timestamptz' })
   created_at: Date;
+
+  /** Populated by findNearby() — not a persisted column. */
+  distanceMeters?: number;
 }
diff --git a/Backend/src/gists/gist.repository.ts b/Backend/src/gists/gist.repository.ts
index 2bf69cc6..46893621 100644
--- a/Backend/src/gists/gist.repository.ts
+++ b/Backend/src/gists/gist.repository.ts
@@ -96,7 +96,7 @@ export class GistRepository {
 
     const extraWhere = clauses.length > 0 ? `AND ${clauses.join(' AND ')}` : '';
 
-    const items = await this.dataSource.query<Gist[]>(
+    const rows = await this.dataSource.query<Array<Gist & { distance_meters: string }>>(
       `
       SELECT
         g.id,
@@ -110,22 +110,28 @@ export class GistRepository {
         ST_X(g.location::geometry)                              AS lon,
         ST_Y(g.location::geometry)                              AS lat,
         ST_Distance(
-          g.location,
+          g.location::geography,
           ST_SetSRID(ST_MakePoint($1, $2), 4326)::geography
         )                                                        AS distance_meters
       FROM gists g
       WHERE ST_DWithin(
-        g.location,
+        g.location::geography,
         ST_SetSRID(ST_MakePoint($1, $2), 4326)::geography,
         $3
       )
+      AND g.expires_at > NOW()
       ${extraWhere}
-      ORDER BY g.created_at DESC
+      ORDER BY distance_meters ASC, g.created_at DESC
       LIMIT $4
       `,
       params,
     );
 
+    const items: Gist[] = rows.map((r) => ({
+      ...r,
+      distanceMeters: parseFloat(r.distance_meters),
+    }));
+
     return PaginationHelper.buildResponse(items, limit);
   }
 
diff --git a/Backend/src/gists/gists.service.ts b/Backend/src/gists/gists.service.ts
index edae0882..8812604a 100644
--- a/Backend/src/gists/gists.service.ts
+++ b/Backend/src/gists/gists.service.ts
@@ -1,7 +1,6 @@
-import { Injectable, Logger } from '@nestjs/common';
+import { Injectable, Logger, NotFoundException } from '@nestjs/common';
 import { InjectDataSource } from '@nestjs/typeorm';
 import { DataSource } from 'typeorm';
-import { Injectable, Logger, NotFoundException } from '@nestjs/common';
 import { CreateGistDto } from './dto/create-gist.dto';
 import { QueryGistsDto } from './dto/query-gists.dto';
 import { GistRepository, PG_UNIQUE_VIOLATION } from './gist.repository';
@@ -86,16 +85,6 @@ export class GistsService {
       }
       throw err;
     }
-    return this.gistRepository.create({
-      content,
-      lat: dto.lat,
-      lon: dto.lon,
-      location_cell: locationCell,
-      content_hash: cid,
-      stellar_gist_id: gistId,
-      tx_hash: txHash,
-      author_address: dto.author,
-    });
   }
 
   async findNearby(query: QueryGistsDto): Promise<PaginatedResponse<Gist>> {