From 289cf9b4db283492cac936b21cce1d58b6ac21ca Mon Sep 17 00:00:00 2001
From: Lakshmi Murugappan <lakshmi.murugappan@tngtech.com>
Date: Tue, 2 Sep 2025 16:09:00 +0100
Subject: [PATCH] Remove fuzzy-search from cascading PDS search algorithm

We have seen at least two cases where fuzzy matching in PDS returned a patient that was obviously wrong (first name and last name swapped around and spellings completely different, and postcode different). We think it is safest to remove the last search step (fuzzy step) from the cascading search
---
 app/jobs/process_patient_changesets_job.rb    | 19 ++++---------------
 spec/factories/patient_changesets.rb          |  2 +-
 ...port_child_pds_lookup_extravaganza_spec.rb | 12 ++----------
 .../process_patient_changesets_job_spec.rb    |  9 +++++----
 4 files changed, 12 insertions(+), 30 deletions(-)

diff --git a/app/jobs/process_patient_changesets_job.rb b/app/jobs/process_patient_changesets_job.rb
index f1ef85ee9b..706e0cbf35 100644
--- a/app/jobs/process_patient_changesets_job.rb
+++ b/app/jobs/process_patient_changesets_job.rb
@@ -79,7 +79,7 @@ def steps
         too_many_matches: :no_fuzzy_without_history
       },
       no_fuzzy_without_history: {
-        no_matches: :fuzzy,
+        no_matches: :give_up,
         one_match: :save_nhs_number_if_unique,
         too_many_matches: :give_up,
         format_query: ->(query) { query.merge(history: false) }
@@ -98,22 +98,11 @@ def steps
         format_query: ->(query) { query[:given_name][3..] = "*" }
       },
       no_fuzzy_with_wildcard_family_name: {
-        no_matches: :fuzzy,
-        one_match: :fuzzy,
-        too_many_matches: :fuzzy,
-        skip_step: :fuzzy,
-        format_query: ->(query) { query[:family_name][3..] = "*" }
-      },
-      fuzzy: {
-        no_matches: :give_up,
+        no_matches: :save_nhs_number_if_unique,
         one_match: :save_nhs_number_if_unique,
         too_many_matches: :save_nhs_number_if_unique,
-        format_query: ->(query) do
-          query[:fuzzy] = true
-          # For fuzzy searches, history is the default. We get an error if we
-          # try to set it to true explicitly
-          query[:history] = nil
-        end
+        skip_step: :save_nhs_number_if_unique,
+        format_query: ->(query) { query[:family_name][3..] = "*" }
       }
     }
   end
diff --git a/spec/factories/patient_changesets.rb b/spec/factories/patient_changesets.rb
index 01e777c80a..9da0e1f2a3 100644
--- a/spec/factories/patient_changesets.rb
+++ b/spec/factories/patient_changesets.rb
@@ -46,7 +46,7 @@
       {
         child: {
           "given_name" => "John",
-          "family_name" => "Doe",
+          "family_name" => "Dover",
           "date_of_birth" => "2010-01-01",
           "address_postcode" => "SW1A 1AA",
           "nhs_number" => nil
diff --git a/spec/features/import_child_pds_lookup_extravaganza_spec.rb b/spec/features/import_child_pds_lookup_extravaganza_spec.rb
index 0b09bc0894..27f6a4b9c3 100644
--- a/spec/features/import_child_pds_lookup_extravaganza_spec.rb
+++ b/spec/features/import_child_pds_lookup_extravaganza_spec.rb
@@ -350,7 +350,7 @@ def and_pds_lookup_during_import_is_enabled
       address_postcode: "B1 1AA",
       steps: {
         wildcard_postcode: "1111111111",
-        fuzzy: "9435726097"
+        wildcard_family_name: "9435726097"
       }
     )
   end
@@ -387,13 +387,6 @@ def stub_pds_cascading_search(
         "given" => given_name,
         "birthdate" => birthdate,
         "address-postalcode" => address_postcode
-      },
-      fuzzy: {
-        "family" => family_name,
-        "given" => given_name,
-        "birthdate" => birthdate,
-        "address-postalcode" => address_postcode,
-        "_fuzzy-match" => "true"
       }
     }.each do |step, query|
       if steps[step]
@@ -827,14 +820,13 @@ def then_maia_has_the_uploaded_nhs_number
 
   def and_maia_has_multiple_pds_search_results
     maia = Patient.find_by(given_name: "Maia", family_name: "Smith")
-    expect(maia.pds_search_results.count).to eq(5)
+    expect(maia.pds_search_results.count).to eq(4)
     expect(maia.pds_search_results.pluck(:step)).to eq(
       %w[
         no_fuzzy_with_history
         no_fuzzy_with_wildcard_postcode
         no_fuzzy_with_wildcard_given_name
         no_fuzzy_with_wildcard_family_name
-        fuzzy
       ]
     )
   end
diff --git a/spec/jobs/process_patient_changesets_job_spec.rb b/spec/jobs/process_patient_changesets_job_spec.rb
index dbcdf9bae3..9d54133b08 100644
--- a/spec/jobs/process_patient_changesets_job_spec.rb
+++ b/spec/jobs/process_patient_changesets_job_spec.rb
@@ -68,8 +68,8 @@
     end
   end
 
-  context "when a later fuzzy search finds a match" do
-    let(:step) { :fuzzy }
+  context "when a later wildcard-family-name search finds a match" do
+    let(:step) { :no_fuzzy_with_wildcard_family_name }
 
     before do
       patient_changeset["pending_changes"]["search_results"] = [
@@ -94,8 +94,8 @@
     end
   end
 
-  context "when fuzzy search returns conflicting NHS numbers" do
-    let(:step) { :fuzzy }
+  context "when wildcard-family-name search returns conflicting NHS numbers" do
+    let(:step) { :no_fuzzy_with_wildcard_family_name }
 
     before do
       patient_changeset["pending_changes"]["search_results"] = [
@@ -115,6 +115,7 @@
       perform
 
       expect(patient_changeset.child_attributes["nhs_number"]).to be_blank
+      expect(patient_changeset.pds_nhs_number).to be_nil
     end
   end