[CALCITE-5764] Puffin, an Awk for Java

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.35.0
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 07/Jun/23 21:04
• Updated: 27/Jul/23 10:22
• Resolved: 28/Jun/23 19:14

Description

Create Puffin, which allows a programming model similar to the awk scripting language.

An awk program is a collection of rules, each of which is a pair: a predicate and an action. For each line in a file, the rules are applied in sequence, and if the predicate evaluates to true, the action is executed. Then awk goes on to the next file.

Here is a simple awk script that counts the number of non-comment lines in a file:

/^#/ {
  ++n;
}
END {
  printf("counter: %d\n", n);
}

Here is the equivalent Puffin program:

    Puffin.Program<Unit> program =
        Puffin.builder(() -> Unit.INSTANCE, u -> new AtomicInteger())
            .add(line -> !line.startsWith("#"),
                line -> line.state().incrementAndGet())
            .after(context ->
                context.println("counter: " + context.state().get()))
            .build();

In Puffin, each predicate is a Predicate<Line>>, and each action is a Consumer<Line>. Line is a data structure that gives access to the text of the line, regular expression matching, and file-local and global state.

Puffin allows thread-safe parallel processing of multiple files (or more generally sources, including URLs). File-local state is allocated by a factory, and each file is processed in a single thread. Therefore rules do not need to coordinate with rules processing other files.

Global state is also allocated by a factory, but it is shared, and rules must coordinate when they access it. In the above example, u -> new AtomicInteger() is the factory that creates global state.

Issue Links

• is related to: CALCITE-5765 Add LintTest, to apply custom lint rules to source code