tuned signature: build_log db is specific to PostgreSQL;

--- a/src/Pure/Admin/build_log.scala	Thu Aug 25 15:30:21 2022 +0200
+++ b/src/Pure/Admin/build_log.scala	Thu Aug 25 15:52:42 2022 +0200
@@ -718,7 +718,7 @@
 
     /* recent entries */
 
-    def recent_time(days: Int): SQL.Source =
+    def recent_time(days: Int): PostgreSQL.Source =
       "now() - INTERVAL '" + days.max(0) + " days'"
 
     def recent_pull_date_table(
@@ -744,7 +744,7 @@
            else "")))
     }
 
-    def select_recent_log_names(days: Int): SQL.Source = {
+    def select_recent_log_names(days: Int): PostgreSQL.Source = {
       val table1 = meta_info_table
       val table2 = recent_pull_date_table(days)
       table1.select(List(log_name), distinct = true) + SQL.join_inner + table2.query_named +
@@ -755,8 +755,8 @@
       days: Int,
       rev: String = "",
       afp_rev: Option[String] = None,
-      sql: SQL.Source = ""
-    ): SQL.Source = {
+      sql: PostgreSQL.Source = ""
+    ): PostgreSQL.Source = {
       val afp = afp_rev.isDefined
       val version = Prop.isabelle_version
       val table1 = recent_pull_date_table(days, rev = rev, afp_rev = afp_rev)

--- a/src/Pure/Admin/build_status.scala	Thu Aug 25 15:30:21 2022 +0200
+++ b/src/Pure/Admin/build_status.scala	Thu Aug 25 15:52:42 2022 +0200
@@ -36,7 +36,7 @@
       options: Options,
       columns: List[SQL.Column],
       only_sessions: Set[String]
-    ): SQL.Source = {
+    ): PostgreSQL.Source = {
       Build_Log.Data.universal_table.select(columns, distinct = true,
         sql = "WHERE " +
           Build_Log.Data.pull_date(afp) + " > " + Build_Log.Data.recent_time(days(options)) +

--- a/src/Pure/Admin/isabelle_cronjob.scala	Thu Aug 25 15:30:21 2022 +0200
+++ b/src/Pure/Admin/isabelle_cronjob.scala	Thu Aug 25 15:52:42 2022 +0200
@@ -110,7 +110,7 @@
     days: Int,
     rev: String,
     afp_rev: Option[String],
-    sql: SQL.Source
+    sql: PostgreSQL.Source
   ): List[Item] = {
     val afp = afp_rev.isDefined
     val select =
@@ -150,7 +150,7 @@
     afp: Boolean = false,
     bulky: Boolean = false,
     more_hosts: List[String] = Nil,
-    detect: SQL.Source = "",
+    detect: PostgreSQL.Source = "",
     active: Boolean = true
   ) {
     def ssh_session(context: SSH.Context): SSH.Session =
@@ -158,7 +158,7 @@
         proxy_host = proxy_host, proxy_user = proxy_user, proxy_port = proxy_port,
         permissive = proxy_host.nonEmpty)
 
-    def sql: SQL.Source =
+    def sql: PostgreSQL.Source =
       Build_Log.Prop.build_engine.toString + " = " + SQL.string(Build_History.engine) + " AND " +
       SQL.member(Build_Log.Prop.build_host.ident, host :: more_hosts) +
       (if (detect == "") "" else " AND " + SQL.enclose(detect))