Check the session's backend_start for cancelling or terminating sessions (#48929)

## Context

Related to database connections - specifically for cancelling queries or
terminating sessions

PIDs can be re-used, so a more accurate check is to use both PID and
`backend_start` to uniquely identify the session to cancel or terminate

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Improved query cancellation and session termination reliability by
verifying the active database session before taking action.
* Prevented actions from affecting a different session that reused the
same process ID.
* Added clearer guidance to refresh when a session has changed or is no
longer available.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/studio/components/interfaces/Observability/DatabaseConnections/ActivityRow.tsx

@@ -158,6 +158,7 @@ export const ActivityRow = ({
     try {
       await cancelQuery({
         pid: activity.pid,
+        backendStart: activity.backend_start,
         projectRef: project?.ref,
         connectionString: project?.connectionString,
       })
@@ -183,6 +184,7 @@ export const ActivityRow = ({
     try {
       await terminateSession({
         pid: activity.pid,
+        backendStart: activity.backend_start,
         projectRef: project?.ref,
         connectionString: project?.connectionString,
       })

apps/studio/components/interfaces/Observability/DatabaseConnections/DatabaseConnections.utils.test.ts

@@ -31,6 +31,7 @@ const activity = (overrides: ActivityOverrides = {}): DatabaseActivity => ({
   application_name: 'test',
   blocked_by: [],
   query: 'select 1',
+  backend_start: NOW,
   query_start: null,
   transaction_start: null,
   state_change: null,

apps/studio/data/database/activity-query.ts

@@ -67,6 +67,7 @@ export type DatabaseActivity = {
   application_name: string
   blocked_by: number[]
   query: string | null
+  backend_start: string
   query_start: string | null
   transaction_start: string | null
   state_change: string | null

apps/studio/data/sql/cancel-query-mutation.ts

@@ -4,22 +4,34 @@ import { toast } from 'sonner'
 
 import { sqlKeys } from './keys'
 import { executeSql } from '@/data/sql/execute-sql-mutation'
-import type { ResponseError, UseCustomMutationOptions } from '@/types'
+import { ResponseError, type UseCustomMutationOptions } from '@/types'
 
 type QueryCancelVariables = {
   pid: number
+  /** Pass the pid's last-known backend_start to guard against a reused pid matching an unrelated session */
+  backendStart?: string
   projectRef?: string
   connectionString?: string | null
 }
 
-async function cancelQuery({ pid, projectRef, connectionString }: QueryCancelVariables) {
-  const sql = getCancelQuerySQL({ pid })
+async function cancelQuery({
+  pid,
+  backendStart,
+  projectRef,
+  connectionString,
+}: QueryCancelVariables) {
+  const sql = getCancelQuerySQL({ pid, backendStart })
   const { result } = await executeSql({
     projectRef,
     connectionString,
     sql,
     queryKey: ['cancel-query'],
   })
+  if (backendStart !== undefined && result.length === 0) {
+    throw new ResponseError(
+      `Session (PID: ${pid}) has already changed since this list was loaded. Refresh and try again.`
+    )
+  }
   return result
 }
 

apps/studio/data/sql/terminate-session-mutation.ts

@@ -4,26 +4,34 @@ import { toast } from 'sonner'
 
 import { sqlKeys } from './keys'
 import { executeSql } from '@/data/sql/execute-sql-mutation'
-import type { ResponseError, UseCustomMutationOptions } from '@/types'
+import { ResponseError, type UseCustomMutationOptions } from '@/types'
 
 type SessionTerminateVariables = {
   pid: number
+  /** Pass the pid's last-known backend_start to guard against a reused pid matching an unrelated session */
+  backendStart?: string
   projectRef?: string
   connectionString?: string | null
 }
 
 export async function terminateSession({
   pid,
+  backendStart,
   projectRef,
   connectionString,
 }: SessionTerminateVariables) {
-  const sql = getTerminateSessionSQL({ pid })
+  const sql = getTerminateSessionSQL({ pid, backendStart })
   const { result } = await executeSql({
     projectRef,
     connectionString,
     sql,
     queryKey: ['terminate-session'],
   })
+  if (backendStart !== undefined && result.length === 0) {
+    throw new ResponseError(
+      `Session (PID: ${pid}) has already changed since this list was loaded. Refresh and try again.`
+    )
+  }
   return result
 }
 

packages/pg-meta/src/sql/studio/database/activity.ts

@@ -10,6 +10,7 @@ select
   a.query,
   a.wait_event_type,
   a.wait_event,
+  a.backend_start,
   a.xact_start as transaction_start,
   a.query_start,
   a.state_change,

packages/pg-meta/src/sql/studio/sql-editor/abort-query.ts

@@ -1,9 +1,31 @@
 import { literal, safeSql, type SafeSqlFragment } from '../../../pg-format'
 
-export const getCancelQuerySQL = ({ pid }: { pid: number }): SafeSqlFragment => {
-  return safeSql`select pg_cancel_backend(${literal(pid)})`
+export const getCancelQuerySQL = ({
+  pid,
+  backendStart,
+}: {
+  pid: number
+  backendStart?: string
+}): SafeSqlFragment => {
+  return safeSql`
+select pg_cancel_backend(pid) as cancelled
+from pg_stat_activity
+where pid = ${literal(pid)}
+${backendStart ? safeSql`and backend_start = ${literal(backendStart)}::timestamptz` : safeSql``}
+`
 }
 
-export const getTerminateSessionSQL = ({ pid }: { pid: number }): SafeSqlFragment => {
-  return safeSql`select pg_terminate_backend(${literal(pid)})`
+export const getTerminateSessionSQL = ({
+  pid,
+  backendStart,
+}: {
+  pid: number
+  backendStart?: string
+}): SafeSqlFragment => {
+  return safeSql`
+select pg_terminate_backend(pid) as terminated
+from pg_stat_activity
+where pid = ${literal(pid)}
+${backendStart ? safeSql`and backend_start = ${literal(backendStart)}::timestamptz` : safeSql``}
+`
 }