From 8d109bccb5f90afe449b3bad1b26818e5637464c Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sun, 29 Mar 2020 10:29:46 +0100
Subject: [PATCH] Handle NULL better insert-missing-data-and-return-all-ids
 queries

Actually check if fields can be NULL, and if they can be then include some
extra conditions for the comparison.

This will at least make the queries smaller, I'm not sure if it will have an
effect on performance.
---
 guix-data-service/model/utils.scm | 45 +++++++++++++++++++++++++------
 1 file changed, 37 insertions(+), 8 deletions(-)

diff --git a/guix-data-service/model/utils.scm b/guix-data-service/model/utils.scm
index 3b256f1..5676c23 100644
--- a/guix-data-service/model/utils.scm
+++ b/guix-data-service/model/utils.scm
@@ -162,6 +162,23 @@ WHERE table_name = $1"
        (error
         (simple-format #f "error: unknown type for value: ~A" v)))))
 
+  (define schema-details
+    (table-schema conn table-name))
+
+  (define (field-can-be-null? field)
+    (match (find (lambda (column-data)
+                   (string=? field
+                             (car column-data)))
+                 schema-details)
+      ((column-name data-type is-nullable?) is-nullable?)
+      (#f
+       (simple-format
+        (current-error-port)
+        "error: couldn't find data for ~A in ~A\n"
+        field
+        schema-details)
+       (error "error: field-can-be-null?"))))
+
   (define select-query
     (string-append
      "SELECT id, "
@@ -187,10 +204,15 @@ WHERE table_name = $1"
      "ON "
      (string-join
       (map (lambda (field)
-             (string-append
-              "(" table-name "." field " = vals." field
-              " OR (" table-name "." field " IS NULL AND"
-              " vals." field " IS NULL))"))
+             (string-concatenate
+              `("("
+                ,table-name "." ,field " = vals." ,field
+                ,@(if (field-can-be-null? field)
+                      `(" OR (" ,table-name "." ,field " IS NULL AND"
+                        " vals." ,field " IS NULL"
+                        ")")
+                      '())
+                ")")))
            field-strings)
       " AND ")))
 
@@ -206,10 +228,17 @@ WHERE table_name = $1"
      " ON "
      (string-join
       (map (lambda (field)
-             (string-append
-              "(" table-name "." field " = " temp-table-name "." field
-              " OR (" table-name "." field " IS NULL AND"
-              " " temp-table-name "." field " IS NULL))"))
+             (string-concatenate
+              `("("
+                ,table-name "." ,field " = " ,temp-table-name "." ,field
+                ,@(if (field-can-be-null? field)
+                      `(" OR ("
+                        ,table-name "." ,field " IS NULL"
+                        " AND "
+                        ,temp-table-name "." ,field " IS NULL"
+                        ")")
+                      '())
+                ")")))
            field-strings)
       " AND ")))