Re: [IndexedDB] Proposal for async API changes

[Shawn Wilsher]

On 5/17/2010 6:15 PM, Jonas Sicking wrote:

We've created some examples of what using this proposed API would look like:

http://docs.google.com/document/pub?id=1I__XnwvvSwyjvxi-FAAE0ecnUDhk5DF7L2GI6O31o18

we've also implemented the same examples using the currently drafted API:

http://docs.google.com/document/pub?id=1KKMAg_oHLeBvFUWND5km6FJtKi4jWxwKR0paKfZc8vU

And I've gone ahead and converted these samples to WebDatabase language too for comparison purposes (I think, at least. I haven't used it before, and these aren't actual fully runnable demos. If you spot an error, let me know!)

////////////////////////////////
// Initialize database

var db = window.openDatabase("CandyDB", "", "My candy store database",
                             1024);
if (db.version != "1") {
  db.changeVersion(db.version, "1", function(tx) {
    // User's first visit.  Initialize database.
    var tables = [
      { name: "kids", columns: ["id INTEGER PRIMARY KEY",
                                "name TEXT"]},
      { name: "candy", columns: ["id INTEGER PRIMARY KEY",
                                 "name TEXT"]},
      { name: "candySales", columns: ["kidId INTEGER",
                                      "candyId INTEGER",
                                      "date TEXT"]}
    ];

    for (var index = 0; index < tables.length; index++) {
      var table = tables[index];
      tx.executeSql("CREATE TABLE " + table.name + "(" +
                    table.columns.join(", ") + ");",
                    null, tableCreated);
    }
  }, null, function() { loadData(db); });
}
else {
  // User has been here before, no initialization required.
  loadData(db);
}

function loadData(db) {
  // Do stuff!
}

////////////////////////////////
// List kids

var db = window.openDatabase("CandyDB", "1", "My candy store database",
                             1024);
db.readTransaction(function(tx) {
  // Enumerate the entire table.
  tx.executeSql("SELECT * FROM kids", function(tx, results) {
    var rows = results.rows;
    for (var index = 0; index < rows.length; index++) {
      var item = rows.item(index);
      var element = document.createElement("div");
      element.textContent = item.name;
      document.getElementById("kidList").appendChild(element);
    }
  });
});

////////////////////////////////
// Store kids into database

var kids = [
  { name: "Anna" },
  { name: "Betty" },
  { name: "Christine" },
];

var db = window.openDatabase("CandyDB", "1", "My candy store database",
                             1024);
db.transaction(function(tx) {
  for (var index = 0; index < kids.length; index++) {
    var kid = kids[index];
    tx.executeSql("INSERT INTO kids (name) VALUES (:name);", [kid],
                  function(tx, results) {
      document.getElementById("display").textContent =
          "Saved record for " + kid.name + " with id " + results.insertId;
    });
  }
});


////////////////////////////////
// List kids who bought candy, and the number of purchases they made

var db = window.openDatabase("CandyDB", "1", "My candy store database",
                             1024);
db.readTransaction(function(tx) {
  tx.executeSql("SELECT name, count " +
                "FROM kids " +
                "INNER JOIN candySales " +
                "ON kids.id = candySales.kidId;",
                function(tx, results) {
    var rows = results.rows;
    for (var index = 0; index < rows.length; index++) {
      var item = rows.item(index);
      display.textContent += ", " + item.name + "bought " +
                             item.count + "pieces";
    }
  });
});

////////////////////////////////
// List kids who bought candy, and the number of purchases they made
// (some may have bought 0)

var db = window.openDatabase("CandyDB", "1", "My candy store database",
                             1024);
db.readTransaction(function(tx) {
  tx.executeSql("SELECT name, count " +
                "FROM kids " +
                "LEFT JOIN candySales " +
                "ON kids.id = candySales.kidId;",
                function(tx, results) {
    var rows = results.rows;
    for (var index = 0; index < rows.length; index++) {
      var item = rows.item(index);
      display.textContent += ", " + item.name + "bought " +
                             item.count + "pieces";
    }
  });
});


Cheers,

Shawn

It should be noted that WebDatabase fares much better when it comes to joins, but I suspect we all knew that.

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