02/09: Add checks to guard against null data

[Christopher Baines]

cbaines pushed a commit to branch master
in repository data-service.

commit b8abe38352ff0513dee2bae87d3c17eba3c84339
Author: Danjela Lura <danielaluraa@gmail.com>
AuthorDate: Thu May 28 22:27:48 2020 +0200

    Add checks to guard against null data
    
    Signed-off-by: Christopher Baines <mail@cbaines.net>
---
 guix-data-service/model/lint-warning.scm | 30 ++++++++++++++++--------------
 guix-data-service/model/utils.scm        | 22 +++++++++++++---------
 2 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/guix-data-service/model/lint-warning.scm 
b/guix-data-service/model/lint-warning.scm
index f22681b..6c83773 100644
--- a/guix-data-service/model/lint-warning.scm
+++ b/guix-data-service/model/lint-warning.scm
@@ -36,20 +36,22 @@
 (define (insert-guix-revision-lint-warnings conn
                                             guix-revision-id
                                             lint-warning-ids)
-  (exec-query
-   conn
-   (string-append
-    "INSERT INTO guix_revision_lint_warnings (lint_warning_id, 
guix_revision_id) "
-    "VALUES "
-    (string-join
-     (map (lambda (lint-warning-id)
-            (simple-format
-             #f
-             "(~A, ~A)"
-             lint-warning-id
-             guix-revision-id))
-          lint-warning-ids)
-     ", "))))
+  (if (null? lint-warning-ids)
+      '()
+      (exec-query
+       conn
+       (string-append
+        "INSERT INTO guix_revision_lint_warnings (lint_warning_id, 
guix_revision_id) "
+        "VALUES "
+        (string-join
+         (map (lambda (lint-warning-id)
+                (simple-format
+                 #f
+                 "(~A, ~A)"
+                 lint-warning-id
+                 guix-revision-id))
+              lint-warning-ids)
+         ", ")))))
 
 (define* (lint-warnings-for-guix-revision conn commit-hash
                                           #:key
diff --git a/guix-data-service/model/utils.scm 
b/guix-data-service/model/utils.scm
index 5676c23..79aa7da 100644
--- a/guix-data-service/model/utils.scm
+++ b/guix-data-service/model/utils.scm
@@ -317,10 +317,12 @@ WHERE table_name = $1"
                   "ANALYZE " temp-table-name))
 
                 ;; Populate the temporary table
-                (with-time-logging (string-append "populating " 
temp-table-name)
-                  (exec-query conn
-                              (insert-sql data
-                                          #:table-name temp-table-name)))
+                (if (null? data)
+                    '()
+                    (with-time-logging (string-append "populating " 
temp-table-name)
+                      (exec-query conn
+                                  (insert-sql data
+                                              #:table-name temp-table-name))))
                 ;; Use the temporary table to find the existing values
                 (let ((result
                        (with-time-logging
@@ -336,11 +338,13 @@ WHERE table_name = $1"
                   result))
 
               ;; If not using a temporary table, just do a single SELECT query
-              (exec-query->vhash conn
-                                 select-query
-                                 cdr
-                                 (lambda (result)
-                                   (string->number (first result))))))
+              (if (null? data)
+                  '()
+                  (exec-query->vhash conn
+                                     select-query
+                                     cdr
+                                     (lambda (result)
+                                       (string->number (first result)))))))
          (missing-entries
           (filter (lambda (field-values)
                     (not (vhash-assoc