sqldb/sqlc: add metadata schema and queries

Author: ziggie1984

sqldb/migrations.go

@@ -126,6 +126,11 @@ var (
 			Version:       16,
 			SchemaVersion: 13,
 		},
+		{
+			Name:          "000014_metadata",
+			Version:       17,
+			SchemaVersion: 14,
+		},
 	}, migrationAdditions...)
 
 	// ErrMigrationMismatch is returned when a migrated record does not

sqldb/sqlc/metadata.sql.go

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS metadata;

sqldb/sqlc/migrations/000014_metadata.down.sql

@@ -0,0 +1,7 @@
+-- The metadata table stores key/value pairs that describe properties of the
+-- database. It is used to persist and validate invariants across restarts,
+-- such as which Bitcoin network the database was initialised for.
+CREATE TABLE IF NOT EXISTS metadata (
+    key   TEXT PRIMARY KEY,
+    value TEXT NOT NULL
+);

sqldb/sqlc/migrations/000014_metadata.up.sql

@@ -0,0 +1,9 @@
+-- name: SetMetaValue :exec
+INSERT INTO metadata (key, value)
+VALUES ($1, $2)
+ON CONFLICT (key) DO NOTHING;
+
+-- name: GetMetaValue :one
+SELECT value
+FROM metadata
+WHERE key = $1;