Exercise 2: parsing, regex

.gitignore

@@ -16,32 +16,8 @@
 *.log
 *.aux
 *.synctex.gz
+*.class
 
 #ignore thumbnails created by windows
 Thumbs.db
-#Ignore files build by Visual Studio
-*.obj
-*.exe
-*.pdb
-*.user
-*.aps
-*.pch
-*.vspscc
-*_i.c
-*_p.c
-*.ncb
-*.suo
-*.tlb
-*.tlh
-*.bak
-*.cache
-*.ilk
-*.log
-[Bb]in
-[Dd]ebug*/
-*.lib
-*.sbr
-obj/
-[Rr]elease*/
-_ReSharper*/
-[Tt]est[Rr]esult*
+[Bb]in

01/tinydb/samples/Exercise2.java

@@ -0,0 +1,78 @@
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import tinydb.Database;
+import tinydb.Table;
+
+public class Exercise2 {
+
+	// select (*|attribute(,attribute)*)
+	// from relation binding(,relation binding)*
+	// where binding.attribute=(binding.attribute|constant)
+	// (and binding.attribute=(binding.attribute|constant))*
+	public static void main(String[] args) throws java.io.IOException {
+		Database db = Database.open("../data/uni");
+		System.out.println("Enter your query below. Type 'quit' to exit.");
+
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		loop:
+		while(true){
+			String q = br.readLine();
+			if(q.equals("quit")) break;
+			Pattern p = Pattern.compile("select (.+) from (.+) where (.+)");
+			Matcher m = p.matcher(q);
+			if(!m.matches()){
+				System.err.println("Query doesn't match the pattern: "+p.toString());
+				continue;
+			}
+			String selections = m.group(1);
+			String relations = m.group(2);
+			String joincond = m.group(3);
+			// (*|attribute(,attribute)*)
+			p = Pattern.compile("\\*|\\w+(,\\w+)*");
+			if(!p.matcher(selections).matches()){
+				System.err.println("Selections don't match the pattern: "+p.toString());
+				System.err.println("Your input: "+selections);
+				continue;
+			}
+			// relation binding(,relation binding)*
+			p = Pattern.compile("\\w+ \\w+(,\\w+ \\w+)*");
+			if(!p.matcher(relations).matches()){
+				System.err.println("Relations don't match the pattern: "+p.toString());
+				System.err.println("Your input: "+relations);
+				continue;
+			}
+			// binding.attribute=(binding.attribute|constant)
+			// (and binding.attribute=(binding.attribute|constant))*
+			p = Pattern.compile("\\w+\\.\\w+=\\w+(and \\w+\\.\\w+=\\w+)*");
+			if(!p.matcher(joincond).matches()){
+				System.err.println("Join conditions don't match the pattern: "+p.toString());
+				System.err.println("Your input: "+joincond);
+				continue;
+			}
+
+			// TODO save values in file
+
+			// handle relations
+			Map<String, Table> h_rel = new HashMap<String, Table>();
+			String[] a_rel = relations.split(",");
+			for(String s : a_rel){
+				String[] binding = s.split(" ");
+				System.out.println("trying to open "+binding[0]);
+				Table table = db.getTable(binding[0]);
+				if(table == null){ // TODO java.io.IOException: Stream closed
+					System.err.println("Table "+binding[0]+" doesn't exist");
+					continue loop;
+				}
+				h_rel.put(binding[1], table);
+			}
+
+
+			br.close();
+		}
+	}
+}