Push the rest

backend/analytics/internal/db/mssql.go

@@ -0,0 +1,41 @@
+package db
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"log/slog"
+
+	_ "github.com/microsoft/go-mssqldb"
+)
+
+// Open creates an MSSQL connection pool and validates connectivity.
+func Open(ctx context.Context, dsn, name string) (*sql.DB, error) {
+	pool, err := sql.Open("sqlserver", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open %s: %w", name, err)
+	}
+	pool.SetMaxOpenConns(15)
+	pool.SetMaxIdleConns(5)
+	if err := pool.PingContext(ctx); err != nil {
+		return nil, fmt.Errorf("ping %s: %w", name, err)
+	}
+	slog.Info("mssql connected", "db", name)
+	return pool, nil
+}
+
+// QueryFirst runs each SQL query in order, returning rows from the first one
+// that succeeds. Used for schema-fallback queries.
+func QueryFirst(ctx context.Context, pool *sql.DB, queries []string) (*sql.Rows, error) {
+	var lastErr error
+	for _, q := range queries {
+		rows, err := pool.QueryContext(ctx, q)
+		if err != nil {
+			slog.Warn("query variant failed, trying next", "err", err)
+			lastErr = err
+			continue
+		}
+		return rows, nil
+	}
+	return nil, fmt.Errorf("all query variants failed: %w", lastErr)
+}