1 files changed, 13 insertions, 0 deletions
diff --git a/sql/fixes/tax_pkey_duplicate.sql b/sql/fixes/tax_pkey_duplicate.sql
new file mode 100644
index 00000000..f590d8ca
--- /dev/null
+++ b/sql/fixes/tax_pkey_duplicate.sql
@@ -0,0 +1,13 @@
+-- SC: Replaces the primary key of the tax table with a check for if the
+--     combination of chart_id and validto is unique.  An index is added to
+--     check for the case of multiple NULL validto values and fail if that would
+--     result.
+
+ALTER TABLE tax DROP CONSTRAINT tax_pkey;
+ALTER TABLE tax ADD CONSTRAINT tax_unique UNIQUE (chart_id, validto);
+COMMENT ON CONSTRAINT tax_unique ON tax IS
+$$Checks on the base uniqueness of the chart_id, validto combination$$;
+
+CREATE UNIQUE INDEX tax_null_validto_unique_idx ON tax(chart_id) WHERE validto IS NULL;
+COMMENT ON INDEX tax_null_validto_unique_idx ON tax IS
+$$Part of primary key emulation for the tax table, ensures at most one NULL validto for each chart_id$$;