fix(filer/postgres): default to ON CONFLICT upsert to keep tx alive (#9709)

* fix(filer/postgres): default to ON CONFLICT upsert to keep tx alive

A KvPut from the inode-index secondary write could fail with 23505
(duplicate key) inside a rename's transaction, after which the next
statement returned 25P02 and rename surfaced to FUSE as EIO. Default
the postgres upsert query when enableUpsert=true so INSERTs are
idempotent; the enableUpsert=false escape hatch is preserved for
non-PG-compatible backends.

* fix(filer/mysql): default to ON DUPLICATE KEY UPDATE upsert

Same shape as the postgres default: when enableUpsert=true but no
upsertQuery is configured, install a sensible default so the
inode-index KvPut does not waste a duplicate-key roundtrip on every
entry write. Uses the VALUES() form so the default works on MariaDB
and MySQL >=5.7; the MySQL 8.0.19 row-alias form is left to explicit
config.

* fix(filer): default enableUpsert=true for sql stores

The default-template fallback only kicks in when enableUpsert=true,
so minimal configs that omit the flag entirely were still exposed.
Default it on for postgres/postgres2/mysql/mysql2; an explicit false
in filer.toml still wins because SetDefault only fills absent keys.

weed/filer/postgres/postgres_sql_gen.go

@@ -13,6 +13,11 @@ type SqlGenPostgres struct {
 	UpsertQueryTemplate    string
 }
 
+// DefaultUpsertQuery keeps INSERTs idempotent so a duplicate-key failure
+// (23505) cannot poison the surrounding transaction (25P02). Used when the
+// user enables upsert but does not provide their own template.
+const DefaultUpsertQuery = `INSERT INTO "%s" (dirhash,name,directory,meta) VALUES($1,$2,$3,$4) ON CONFLICT (dirhash, name) DO UPDATE SET directory=EXCLUDED.directory, meta=EXCLUDED.meta`
+
 var (
 	_ = abstract_sql.SqlGenerator(&SqlGenPostgres{})
 )