From 2cf73fefc7977538c01b6338f16d58b8bc2fe498 Mon Sep 17 00:00:00 2001
From: Ryan Krage <krage.ryan@gmail.com>
Date: Fri, 17 Nov 2023 20:01:22 +0000
Subject: [PATCH] disallow concurrently / add basic docs

Co-authored-by: Ryan Krage <ryan.krage@getbraintree.com>
---
 README.md                               |  8 ++++++++
 lib/pg_ha_migrations/safe_statements.rb |  4 ++++
 spec/safe_statements_spec.rb            | 12 ++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/README.md b/README.md
index 483af28..23437c3 100644
--- a/README.md
+++ b/README.md
@@ -171,6 +171,14 @@ Unsafely make a column not nullable.
 unsafe_make_column_not_nullable :table, :column
 ```
 
+#### safe\_add\_index\_on\_empty\_table
+
+Safely add an index on a table with zero rows. This will raise an error if the table contains data.
+
+```ruby
+safe_add_index_on_empty_table :table, :column
+```
+
 #### safe\_add\_concurrent\_index
 
 Add an index concurrently.
diff --git a/lib/pg_ha_migrations/safe_statements.rb b/lib/pg_ha_migrations/safe_statements.rb
index 1ea1c15..c6df80d 100644
--- a/lib/pg_ha_migrations/safe_statements.rb
+++ b/lib/pg_ha_migrations/safe_statements.rb
@@ -155,6 +155,10 @@ def unsafe_make_column_not_nullable(table, column, options={}) # options arg is
   end
 
   def safe_add_index_on_empty_table(table, columns, options={})
+    if options[:algorithm] == :concurrently
+      raise ArgumentError, "Cannot call safe_add_index_on_empty_table with :algorithm => :concurrently"
+    end
+
     # Avoids taking out an unnecessary SHARE lock if the table does have data
     _ensure_empty_table!(table)
 
diff --git a/spec/safe_statements_spec.rb b/spec/safe_statements_spec.rb
index fc70564..6a2fa82 100644
--- a/spec/safe_statements_spec.rb
+++ b/spec/safe_statements_spec.rb
@@ -1286,6 +1286,18 @@ def up
             )
           end
 
+          it "raises error when :algorithm => :concurrently provided" do
+            test_migration = Class.new(migration_klass) do
+              def up
+                safe_add_index_on_empty_table :foos, [:bar], algorithm: :concurrently
+              end
+            end
+
+            expect do
+              test_migration.suppress_messages { test_migration.migrate(:up) }
+            end.to raise_error(ArgumentError, "Cannot call safe_add_index_on_empty_table with :algorithm => :concurrently")
+          end
+
           it "raises error when table contains rows" do
             setup_migration = Class.new(migration_klass) do
               def up