Chain Example

SchemaCrawler allows you to run multiple SchemaCrawler commands in sequence (“chaining”) from a single JavaScript script. The script uses a chain object to queue up commands with different output formats and file targets, then executes them all in one pass against the same database connection.

How to Run

Before running this example, complete the setup in Getting Started.

1. Create a file called “chain.js” with the contents shown below.
2. Run the command:

schemacrawler \
  --server postgresql \
  --host postgresql \
  --database schemacrawler \
  --user schemacrawler \
  --password schemacrawler \
  --info-level standard \
  --command script \
  --script share/chain.js

Replace with the connection options for your chosen database. See Getting Started.

This produces two output files in your working directory on the host: - schema.txt — a brief text summary of the schema - schema.png — a visual PNG diagram of the schema

Resource Files

chain.js

Queues two SchemaCrawler commands via chain.addNext(command, outputFormat, outputFile) and then executes them with chain.execute().

var scCommands = function () {

  // Add command to run against the schema metadata
  // Arguments are:
  // 1. --command
  // 2. --output-format
  // 3. --output-file
  chain.addNext("brief", "text", "share/schema.txt");
  chain.addNext("schema", "png", "share/schema.png");

  // Execute the chain, and produce output
  chain.execute();
  
  print('Created files "schema.txt" and "schema.png" in the working directory on the host');
};

scCommands();

Place this file in your working directory. It will be accessible inside the container as share/chain.js.

How to Experiment

1. Add more chain.addNext(...) calls to produce additional outputs — for example, chain.addNext("list", "text", "tables.txt") to list all table names.
2. Change the output format of the schema command to "html" or "svg" to produce a different diagram format.
3. Change the command from "brief" to "details" to include full column and constraint information in the text output.