Stop using adsrc column

Was removed in V12, invalid since V8.

See https://www.postgresql.org/docs/8.3/catalog-pg-attrdef.html

adminer/drivers/pgsql.inc.php

@@ -352,7 +352,7 @@ function fields($table) {
 
  $identity_column = min_version(10) ? "(a.attidentity = 'd')::int" : '0';
 
- foreach (get_rows("SELECT a.attname AS field, format_type(a.atttypid, a.atttypmod) AS full_type, d.adsrc AS default, a.attnotnull::int, col_description(c.oid, a.attnum) AS comment, $identity_column AS identity
+ foreach (get_rows("SELECT a.attname AS field, format_type(a.atttypid, a.atttypmod) AS full_type, pg_get_expr(d.adbin, d.adrelid) AS default, a.attnotnull::int, col_description(c.oid, a.attnum) AS comment, $identity_column AS identity
 FROM pg_class c
 JOIN pg_namespace n ON c.relnamespace = n.oid
 JOIN pg_attribute a ON c.oid = a.attrelid

changes.txt

@@ -1,5 +1,6 @@
 Adminer 4.7.5-dev:
 Add id="" to cells with failed inline edit (bug #708)
+PostgreSQL: Fix getting default value in PostgreSQL 12 (bug #719)
 PostgreSQL, Oracle: Set schema for EXPLAIN queries in SQL command (bug #706)
 ClickHouse: SQL command
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