fix(miniflare): add DumpSqlStats interface and INSERT size tracking

Add stats tracking for INSERT statement sizes to help analyze the impact
of including column names in D1 SQL exports. This syncs the miniflare
dumpSql.ts with the d1-worker version from GitLab MR 1056.

Author: alsuren

packages/miniflare/src/workers/d1/dumpSql.ts

@@ -5,6 +5,23 @@
 // as possible, with any deviations noted.
 import { SqlStorage } from "@cloudflare/workers-types/experimental";
 
+/** Stats tracking for dumpSql. Will be mutated in place if provided. */
+export interface DumpSqlStats {
+	rows_read: number;
+	rows_written: number;
+	// Stats for tracking INSERT statement sizes (column names are always included)
+	/** Number of INSERT statements over 100KB (current size, with column names) */
+	inserts_over_100kb_with_column_names: number;
+	/** Number of INSERT statements that would be over 100KB without column names (for backward comparison) */
+	inserts_already_over_100kb: number;
+	/** Total number of INSERT statements generated */
+	total_inserts: number;
+	/** Maximum INSERT statement size without column names (hypothetical, for backward comparison) */
+	max_insert_size: number;
+	/** Maximum INSERT statement size (current size, with column names) */
+	max_insert_size_with_column_names: number;
+}
+
 export function* dumpSql(
 	db: SqlStorage,
 	options?: {
@@ -13,7 +30,7 @@ export function* dumpSql(
 		tables?: string[];
 	},
 	/** Optional stats tracking. Will be mutated in place if provided */
-	stats?: { rows_read: number; rows_written: number }
+	stats?: DumpSqlStats
 ) {
 	// WARNING: the caller in D1 assumes non-empty exports, so think carefully before removing this initial yield.
 	yield `PRAGMA defer_foreign_keys=TRUE;`;
@@ -84,6 +101,8 @@ export function* dumpSql(
 		const select = `SELECT ${columns.map((c) => escapeId(c.name)).join(", ")} FROM ${escapeId(table)};`;
 		const rows_cursor = db.exec(select);
 		const columnNames = columns.map((c) => escapeId(c.name)).join(",");
+		// The column names portion is: " (" + columnNames + ")" = 3 + columnNames.length
+		const columnNamesOverhead = 3 + columnNames.length;
 		for (const dataRow of rows_cursor.raw()) {
 			const formattedCells = dataRow.map((cell: unknown, i: number) => {
 				const colType = columns[i].type;
@@ -110,7 +129,31 @@ export function* dumpSql(
 				}
 			});
 
-			yield `INSERT INTO ${escapeId(table)} (${columnNames}) VALUES(${formattedCells.join(",")});`;
+			const insertStmt = `INSERT INTO ${escapeId(table)} (${columnNames}) VALUES(${formattedCells.join(",")});`;
+
+			// Track stats for INSERT statement sizes
+			if (stats) {
+				const currentSize = insertStmt.length;
+				// Calculate what the size would be without column names (for comparison)
+				const sizeWithoutColumnNames = currentSize - columnNamesOverhead;
+				const LIMIT = 100 * 1024; // 100KB
+
+				stats.total_inserts++;
+				if (sizeWithoutColumnNames > LIMIT) {
+					stats.inserts_already_over_100kb++;
+				}
+				if (currentSize > LIMIT) {
+					stats.inserts_over_100kb_with_column_names++;
+				}
+				if (sizeWithoutColumnNames > stats.max_insert_size) {
+					stats.max_insert_size = sizeWithoutColumnNames;
+				}
+				if (currentSize > stats.max_insert_size_with_column_names) {
+					stats.max_insert_size_with_column_names = currentSize;
+				}
+			}
+
+			yield insertStmt;
 		}
 		if (stats) {
 			stats.rows_read += rows_cursor.rowsRead;