Update amcheck warnings: recommend clones over standbys

Clones (e.g., restored from backup) are the ideal target for heavy
corruption checks — no replication lag concerns, no risk to production,
and you verify backup integrity at the same time.

Author: NikolayS

README.md

@@ -47,8 +47,8 @@ Then connect to any Postgres server via psql and type `:dba` to open the interac
 | ID | Report |
 |----|--------|
 | c1 | Quick: btree + GIN (PG18) + heap (PG14) check — safe for production (AccessShareLock) |
-| c2 | Parent: btree parent-child check — detects glibc/collation corruption (⚠️ ShareLock) |
-| c3 | Full: heapallindexed + parent + heap — proves every tuple is indexed (⚠️⚠️ slow + ShareLock) |
+| c2 | Parent: btree parent-child check — detects glibc/collation corruption (⚠️ ShareLock — use on clones) |
+| c3 | Full: heapallindexed + parent + heap — proves every tuple is indexed (⚠️⚠️ slow + ShareLock — use on clones) |
 
 ### Memory
 | ID | Report |

sql/c2_amcheck_parent.sql

@@ -1,7 +1,7 @@
--- Corruption: B-tree parent check — detects collation/glibc corruption. ⚠️ ShareLock!
+-- Corruption: B-tree parent check — detects glibc/collation corruption (⚠️ ShareLock, use on clones)
 -- Requires: CREATE EXTENSION amcheck
 -- ⚠️  Takes ShareLock on each index — blocks writes while checking!
--- ⚠️  Best used on STANDBYS or during maintenance windows.
+-- ⚠️  Best used on clones (e.g., restored from backup) or standbys.
 --
 -- Uses bt_index_parent_check() which verifies parent-child key ordering.
 -- This is the most reliable way to detect corruption caused by glibc/ICU
@@ -27,7 +27,7 @@ begin
 
   raise warning '';
   raise warning '⚠️  WARNING: This check takes ShareLock on each index — blocks writes!';
-  raise warning '⚠️  Recommended: run on a STANDBY or during a maintenance window.';
+  raise warning '⚠️  Recommended: run on a clone (e.g., restored from backup), standby, or during maintenance.';
   raise warning '';
   raise notice '=== B-tree parent check (bt_index_parent_check, ShareLock) ===';
   raise notice 'Detects: collation/glibc corruption, parent-child inconsistency, sibling pointer errors';

sql/c3_amcheck_full.sql

@@ -1,7 +1,7 @@
--- Corruption: FULL check — heapallindexed + parent + heap. ⚠️⚠️ SLOW + ShareLock!
+-- Corruption: FULL check — heapallindexed + parent + heap (⚠️⚠️ SLOW + ShareLock, use on clones)
 -- Requires: CREATE EXTENSION amcheck
 -- ⚠️⚠️  HEAVY: Takes ShareLock AND scans entire heap for each index!
--- ⚠️⚠️  This WILL be slow on large databases. Use on STANDBYS only.
+-- ⚠️⚠️  This WILL be slow on large databases. Use on clones (e.g., restored from backup).
 --
 -- bt_index_parent_check with heapallindexed=true: verifies that every single
 -- heap tuple has a corresponding index entry. Catches silent data loss where
@@ -32,7 +32,7 @@ begin
   raise warning '';
   raise warning '⚠️⚠️  WARNING: This is the HEAVIEST corruption check!';
   raise warning '⚠️⚠️  Takes ShareLock on each index (blocks writes) AND scans entire heap.';
-  raise warning '⚠️⚠️  On large databases this can take HOURS. Use on standbys only.';
+  raise warning '⚠️⚠️  On large databases this can take HOURS. Use on clones (e.g., restored from backup).';
   raise warning '';
 
   -- === Full B-tree check ===

start.psql

@@ -11,8 +11,8 @@
 \echo '  b4 – B-tree indexes bloat (requires pgstattuple; expensive)'
 \echo '  b5 – Tables and columns without stats (so bloat cannot be estimated)'
 \echo '  c1 –  Corruption: quick check — btree, GIN (PG18+), heap (PG14+). Safe for production.'
-\echo '  c2 –  Corruption: B-tree parent check — detects collation/glibc corruption. ⚠️ ShareLock!'
-\echo '  c3 –  Corruption: FULL check — heapallindexed + parent + heap. ⚠️⚠️ SLOW + ShareLock!'
+\echo '  c2 –  Corruption: B-tree parent check — detects glibc/collation corruption (⚠️ ShareLock, use on clones)'
+\echo '  c3 –  Corruption: FULL check — heapallindexed + parent + heap (⚠️⚠️ SLOW + ShareLock, use on clones)'
 \echo '  e1 – Extensions installed in current database'
 \echo '  i1 – Unused and rarely used indexes'
 \echo '  i2 – Redundant indexes'