Q116. What is “Spark streaming” in the Spark ecosystem with Spark core, Spark SQL, Spark MLlib, Spark GraphX, etc? A116. Spark is a distributed and scalable batch processing framework that supports in-memory processing in sub-seconds. The batch processes are scheduled with something like Oozie or Unix cron jobs to run...
Problem Statement: How would you go about writing an SQL WHERE clause parser to evaluate a given condition against the given data in a Hashmap. For example:
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public class ParserTest { public static void main(String[] args) throws ParseException { Map<String, Object> data = new HashMap<>(); data.put("Acct1", "1"); data.put("Acct2", "2"); data.put("Acct3", Integer.valueOf("3")); data.put("Acct4", "4"); String whereClause = "Acct4 = '4' AND Acct1 NOT IN ('3', '2') AND Acct2 = '2' AND Acct3 IN (4,3,1)"; TokenStream tokenStream = tokenize(whereClause); //System.out.println(""); Expr expr = parse(tokenStream); boolean result = expr.evaluate(data); System.out.println(result); } |
Outputs:
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result=true |
Solution, step by step Step 1: Let’s write a tokenize method using regular expressions to tokenize the WHERE condition supplied...
This extends Writing a simple SQL where clause parser in Java – Part 1. In the next post, let’s look at the parsing to an Abstract Syntax Tree (i.e. AST logic). Step 5: Firstly the Expr interface that gets implemented by different expressions. … Read more ›...
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