AutoSQL - Automated SQL Insertions for Modern Data Workflows

Now rewritten in TypeScript with an entirely new class-based structure!

🚀 AutoSQL — A Smarter Way to Insert Data

AutoSQL is a TypeScript-powered tool that simplifies and automates the SQL insertion process with intelligent schema prediction, safe table handling, batching, and dialect-specific optimisations for MySQL and PostgreSQL.

🌐 Overview

AutoSQL helps engineers and analysts insert structured or semi-structured JSON into SQL databases (MySQL/PostgreSQL) with zero manual schema prep. It's ideal for:

• No-code/low-code tools that export data as raw JSON
• Rapid data warehousing of API responses or flat files
• Auto-generating schemas with correct types, keys, and indexes

It shines in modern ETL workflows where structure is unpredictable but SQL output is needed.

🔧 New in This Version:

• Full TypeScript support
• Core logic restructured into a reusable Database class-based architecture
• Robust error handling and logging support
• Modular utilities for type prediction, metadata inference, batching, and SSH tunneling

📦 Installation

npm install autosql

📚 Table of Contents

• Supported SQL Dialects
• Quick Start
• Configuration
  • Metadata Format
  • SSH Support
• Insert Options
• Core Interfaces
  • Database Class
• Convenience Utilities
  • Type Inference & Normalisation
  • Config & Metadata Tools
  • Metadata Inference & Preparation
  • Insert Planning & Execution

🧬 Supported SQL Dialects

AutoSQL supports:

• MySQL (via mysql2)
• PostgreSQL (via pg)

Optional support for SSH tunneling is available via:

• ssh2

⚡ Quick Start

import { Database } from 'autosql';

const config = {
  sqlDialect: 'mysql',
  host: 'localhost',
  user: 'root',
  password: 'root',
  database: 'mysql',
  port: 3306
};

const data = [
  { id: 1, name: 'Alice', created_at: '2024-01-01' },
  { id: 2, name: 'Bob', created_at: '2024-01-02' }
];

let db: Database;

db = Database.create(config);
await db.establishConnection();

// Option 1: Direct insert if schema already exists or is managed externally
await db.autoInsertData({ table: 'target_table', data });

// Option 2: Fully automated schema + insert workflow
await db.autoSQL('target_table', data);

await db.closeConnection();

AutoSQL will:

• Infer metadata and key structure
• Create or alter the target table
• Batch insert rows
• Handle dialect-specific quirks automatically
• Automatically manage timestamps and optional history tracking (if configured)

⚙️ Configuration

export interface DatabaseConfig {
  // Required connection settings
  sqlDialect: 'mysql' | 'pgsql';
  host?: string;
  user?: string;
  password?: string;
  database?: string;
  port?: number;

  // Optional table target
  // ALL SETTINGS BELOW HERE ARE OPTIONAL
  schema?: string;
  table?: string;

  // Metadata control
  metaData?: { [tableName: string]: MetadataHeader };
  existingMetaData?: { [tableName: string]: MetadataHeader };
  updatePrimaryKey?: boolean;
  primaryKey?: string[];

  // Table creation and charset settings
  engine?: string;
  charset?: string;
  collate?: string;
  encoding?: string;

  // Type inference controls
  pseudoUnique?: number; // The % of values that must be unique to be considered pseudoUnique. - defaults to 0.9 (90%)
  autoIndexing?: boolean; // Automatically identify and add indexes to tables when altering / creating - defaults to TRUE
  decimalMaxLength?: number; // Automatically round decimals to a maximum of X decimal places - defaults to 10
  maxKeyLength?: number; // Limits indexes / primary keys from using columns that are longer than this length - defaults to 255
  maxVarcharLength?: number; // Prevents varchar columns from exceeding this length, autoconverts this length of varchar to text columns -- defaults to 1024 characters

  // Sampling controls
  sampling?: number; // If provided data exceeds samplingMinimum rows, we sample this % of values for identifying uniques and column types — defaults to 0, allows values between 0 and 1
  samplingMinimum?: number; // If provided data exceeds this row count, sampling kicks in — defaults to 100

  // Insert strategy
  insertType?: 'UPDATE' | 'INSERT'; // UPDATE automatically replaces non-primary key values with new values that are found
  insertStack?: number; // Maximum number of rows to insert in one query - defaults to 100
  safeMode?: boolean; // Prevent the altering of tables if needed - defaults to false
  deleteColumns?: boolean; // Drop columns if needed - defaults to false

  // Timestamp columns
  addTimestamps?: boolean; // If TRUE, runs function ensureTimestamps as part of AutoSQL function. Which adds a dwh_created_at, dwh_modified_at and dwh_loaded_at timestamp columns that are automatically filled. -- defaults to TRUE

    // Optional advanced insert modes
  useStagingInsert?: boolean; // Enable temporary staging table insert pattern (if supported) -- defaults to TRUE
  addHistory?: boolean; // Automatically duplicate rows into history tables before overwrites -- defaults to FALSE
  historyTables?: string[]; // Names of the tables to have history tracked -- pairs with addHistory above
  autoSplit?: boolean; // Automatically split large datasets (columns) across multiple tables if needed
  addNested?: boolean; // Extracts nested JSON values into separate tables with composite primary keys -- defaults to FALSE
  nestedTables?: string[]; // Nested Table names to apply nested extraction on -- if nesting `columnA` on `tableB`, this would be [`tableB_columnA`]

  // Performance scaling
  useWorkers?: boolean;
  maxWorkers?: number;

  // SSH tunneling support
  sshConfig?: SSHKeys;
  sshStream?: ClientChannel | null;
  sshClient?: SSHClient;
}

🧠 Metadata Format

AutoSQL can infer metadata from your data, or you can specify it manually:

meta_data: [
  {
    created_at: {
      type: 'datetime',
      length: 0,
      allowNull: true,
      default: 'CURRENT_TIMESTAMP',
      index: true
    }
  },
  {
    name: {
      type: 'varchar',
      length: 50,
      allowNull: false,
      unique: true,
      primary: true
    }
  }
]

🔐 SSH Support

AutoSQL supports SSH tunneling for connecting to remote MySQL or PostgreSQL servers via an intermediate gateway.

Include the SSH configuration inside your DatabaseConfig object under the sshConfig key. AutoSQL will automatically establish the tunnel when establishConnection() is called.

const config: DatabaseConfig = {
  ...
  sshConfig: {
    username: 'ssh_user',
    host: 'remote_host',
    port: 22,
    password: 'password',
    private_key: 'PRIVATE_KEY_STRING',
    private_key_path: '/path/to/key.pem',
    source_address: 'localhost',
    source_port: 3306,
    destination_address: 'remote_sql_host',
    destination_port: 3306
  }
}

  const db = Database.create(config);
  await db.establishConnection();
  // Tunnel is now active and DB connection is routed through it

📑 Insert Options

These control how data is batched, inserted, and optionally how schema alterations are handled.

Basic Insert Options

• insertType: 'UPDATE' | 'INSERT'
  Determines behaviour on duplicate keys. UPDATE replaces non-primary key values with new ones. Defaults to 'INSERT'.

• insertStack: number
  Maximum number of rows to insert in a single query. Defaults to 100.

• safeMode: boolean
  If true, prevents any table alterations during runtime. Defaults to false.

• deleteColumns: boolean
  Allows dropping of existing columns when altering tables. Defaults to false.

⏱ Timestamp Columns

• addTimestamps: boolean
  If true, automatically adds and manages the following timestamp columns:
  • dwh_created_at,
  • dwh_modified_at,
  • dwh_loaded_at
    These are injected and updated during insert operations. Defaults to true. This will also check a variety of common timestamp columns and will only add the equivalent if they do not exist in the existing data. As an example, modified timestamps will check modified_at, modify_at, modified_date, update_date etc.

🧪 Advanced Insert Modes

• useStagingInsert: boolean
  Enables a staging table strategy where data is first inserted into a temporary table before being merged into the target. Useful for large or high-concurrency environments. Defaults to true.

• addHistory: boolean
  If enabled, before overwriting rows (in UPDATE mode), AutoSQL writes the previous version into a corresponding history table. Defaults to false.

• historyTables: string[]
  List of table names to track with history inserts. Used in conjunction with addHistory.

• autoSplit: boolean
  Automatically splits datasets across multiple tables when the row size or column count exceeds allowed limits. Prevents failed inserts due to row size limits. Defaults to false

• addNested: boolean
  If enabled, AutoSQL will extract nested objects or arrays from a field and insert them into a separate table.
  Defaults to false.

• nestedTables: string[]
  Used in conjunction with addNested. Specifies which nested structures should be extracted and written into their own relational tables.

  Format: Each entry should follow the pattern: "<tableName>_<columnName>"

  For each entry:

  • If the dataset includes a table that matches <tableName>,
  • And that table contains a column named <columnName>,
  • And the column contains a JSON object or an array of JSON objects,
  • AutoSQL will extract the nested structure into a new table named <tableName>_<columnName>

  Behavior:

  • The new nested table will include the parent row’s primary key (e.g., row1_id) to maintain relationships
  • The nested object will define the child table’s schema
  • Arrays will be flattened—each item becomes a separate row in the nested table

🧵 Scaling & Workers

• useWorkers: boolean
  Enables parallel worker threads for inserting batches. Improves performance with large datasets. Defaults to true

• maxWorkers: number
  Maximum number of concurrent workers to use during insertion. Must be used with useWorkers. Defaults to 8

🏁 Core Classes: Database (with AutoSQL Utilities)

The Database class is the primary entry point into AutoSQL's workflow. It handles connection management and exposes high-level autoSQL methods for automated insertions, table creation, and metadata handling.

import { Database } from 'autosql';

const db = Database.create(config);
await db.establishConnection();

await db.autoConfigureTable(
  'target_table', // table name
  sampleData,     // raw input data
  null,           // optional existing metadata
  initialMeta     // optional manually defined metadata
);

This is the core interface for managing connections, generating queries, and executing inserts.

⚙️ Database Class

🔸 Static Method

• Database.create(config) – Returns an instance of either MySQLDatabase or PostgresDatabase based on config.

🔹 Core Methods

• getConfig() – Returns the full DatabaseConfig used to initialise this instance.
• updateSchema(schema: string) – Updates the current schema name being used.
• getDialect() – Returns the SQL dialect (mysql or pgsql).
• establishConnection() – Creates and stores a live database connection.
• testConnection() – Attempts to connect and returns success as a boolean.
• runQuery(queryOrParams: QueryInput | QueryInput[]) – Executes a SQL query or list of queries.
• startTransaction() / commit() / rollback() – Manages manual transaction blocks.
• runTransaction(queries: QueryInput[]) – Runs multiple queries inside a single transaction.
• runTransactionsWithConcurrency(queryGroups: QueryInput[][]) – Runs multiple query batches in parallel.
• closeConnection() – Safely closes the active DB connection.

🔹 Table and Schema Methods

• checkSchemaExists(schemaName: string) – Returns whether the given schema exists.
• createSchema(schemaName: string) – Creates the schema if it doesn't exist already.
• createTableQuery(table: string, headers: MetadataHeader) – Returns QueryInput[] to create a table.
• alterTableQuery(table: string, oldHeaders: MetadataHeader, newHeaders: MetadataHeader) – Returns QueryInput[] to alter an existing table.
• dropTableQuery(table: string) – Returns a QueryInput to drop a table.
• getTableMetaData(schema: string, table: string) – Fetches current metadata from the DB for a given table.

🔹 AutoSQL Methods (Exposed on db)

• autoSQL(table: string, data: Record<string, any>[], schema?: string, primaryKey?: string[])
  The simplest way to handle everything — metadata inference, schema changes, batching, inserting, history, workers, and nested structures — in one call.
  Designed for production-ready automation and one-liner ingestion.

• autoInsertData(inputOrTable: InsertInput | string, inputData?: Record<string, any>[], inputMetaData?: MetadataHeader, inputPreviousMetaData?: AlterTableChanges | MetadataHeader | null, inputComparedMetaData?: { changes: AlterTableChanges, updatedMetaData: MetadataHeader }, inputRunQuery = true, inputInsertType?: 'UPDATE' | 'INSERT')
  Executes a full insert using the dialect-aware batching engine.
  If inputRunQuery is true, queries are executed via runTransactionsWithConcurrency().
  If false, a list of insert queries (QueryInput[]) is returned without running them.

• autoConfigureTable(inputOrTable: InsertInput | string, data?: Record<string, any>[], currentMeta?: MetadataHeader, newMeta?: MetadataHeader, runQuery = true)
  Determines whether a table should be created or altered based on metadata comparison.
  If runQuery is true, schema changes are applied immediately via runTransactionsWithConcurrency().
  If false, queries are returned for inspection.

• autoCreateTable(table: string, newMetaData: MetadataHeader, tableExists?: boolean, runQuery = true)
  Creates a new table with the provided metadata.
  If runQuery is false, returns the CREATE TABLE queries without executing them.

• autoAlterTable(table: string, tableChanges: AlterTableChanges, tableExists?: boolean, runQuery = true)
  Alters an existing table using a computed diff.
  Like above, runQuery controls whether to return or execute the queries.

• fetchTableMetadata(table: string)
  Looks up metadata for the given table and returns { currentMetaData, tableExists }.
  Used internally for decisions about schema creation or alteration.

• splitTableData(table: string, data: Record<string, any>[], metaData: MetadataHeader)
  If autoSplit is enabled, splits a wide dataset across multiple smaller tables.
  Returns an array of InsertInput instructions for multi-table insert execution.

• handleMetadata(table: string, data: Record<string, any>[], primaryKey?: string[])
  Combines metadata inference and comparison into one call.
  Returns an object with:

  • currentMetaData: existing table metadata from the DB
  • newMetaData: metadata inferred from new data
  • mergedMetaData: result of merging existing and new metadata
  • initialComparedMetaData: diff result, if any
  • changes: schema changes needed for alignment

• getMetaData(config: DatabaseConfig, data: Record<string, any>[], primaryKey?: string[])
  Analyses sample data and returns a metadata map with type, length, nullability, uniqueness, and key suggestions.

• compareMetaData(oldMeta: MetadataHeader, newMeta: MetadataHeader)
  Compares two metadata structures and returns:

  • changes: an AlterTableChanges diff object
  • updatedMetaData: the merged metadata structure

Each method is designed to work with the same Database instance.

🧰 Convenience Utilities

AutoSQL exposes utilities that power autoSQL and can be used independently. These include metadata analysis, SQL formatting, batching, config validation, and more.

🔍 Type Inference & Normalisation

• predictType(value) – Predicts SQL-compatible type (varchar, datetime, int, etc.) based on a single input value.
• collateTypes(typeSetOrArray) – Accepts a Set or Array of types and returns a single compatible SQL type.
• normalizeNumber(input, thousands, decimal) – Standardises numeric values to SQL-safe format with optional locale indicators.
• calculateColumnLength(column, value, sqlLookup) – Dynamically computes and updates column length and decimal precision based on input data.
• shuffleArray(array) – Randomly reorders an array (used for sampling).
• isObject(val) – Type-safe check to determine if a value is a non-null object.

⚙️ Config & Metadata Tools

• validateConfig(config) – Validates and merges the provided DatabaseConfig with default settings.
• mergeColumnLengths(lengthA, lengthB) – Chooses the greater length definition between two metadata column states.
• setToArray(set) – Converts a Set to a regular array.
• normalizeKeysArray(keys) – Flattens and sanitizes arrays of key strings (e.g., for primary keys).
• isValidDataFormat(data) – Checks if the input is a valid array of plain objects suitable for inserts.

🧠 Metadata Inference & Preparation

• initializeMetaData(headers) – Constructs a default metadata object from column headers with default flags and null types.
• getDataHeaders(data, config) – Scans sample data to derive column names and infer initial metadata.
• predictIndexes(metaData, maxKeyLength?, primaryKey?, sampleData?) – Suggests primary keys, unique constraints, and indexes based on uniqueness, length limits, or configured priorities.
• updateColumnType(existingMeta, newValue) – Adjusts the type and attributes of a column based on new sample input.

📦 Insert Planning & Execution

• splitInsertData(data, config) – Splits large datasets into batches that meet size and row count constraints.
• getInsertValues(metaData, row, dialectConfig) – Extracts a single row's values as a SQL-safe array, accounting for dialect-specific formatting.
• organizeSplitData(data, splitMetaData) – Partitions the dataset by metadata groups for multiple table insert strategies.
• organizeSplitTable(table, newMetaData, currentMetaData, dialectConfig) – Generates split metadata configurations based on structural divergence.
• estimateRowSize(metaData, dialect) – Estimates the byte size of a row using provided metadata and flags potential overflows.
• parseDatabaseMetaData(rows, dialectConfig?) – Transforms SQL column descriptions into AutoSQL-compatible metadata.
• tableChangesExist(alterTableChanges) – Returns true if the proposed table changes indicate schema modification is needed.
• isMetaDataHeader(obj) – Type guard to check if an object qualifies as a metadata header.
• isValidDataFormat(data) – Validates that the input is an array of row objects suitable for processing.

📬 Feedback

This library is under active development. Suggestions, issues, and contributions are welcome.

Contact: w@walterchoi.com