[tracker] SPARQL: Improve predicate variable support

[Jürg Billeter <juergbi src gnome org>]

commit 960a5faf18a3f2a87fa494880d9918731eb48326
Author: Jürg Billeter <j bitron ch>
Date:   Wed Dec 29 17:28:50 2010 +0100

    SPARQL: Improve predicate variable support
    
    This allows use of object from predicate variable pattern as subject in
    other patterns.
    
    Fixes NB#212736.

 src/libtracker-data/tracker-sparql-expression.vala |    1 -
 src/libtracker-data/tracker-sparql-pattern.vala    |   19 +++++++++++++++++--
 tests/libtracker-data/aggregates/aggregate-1.out   |    2 +-
 .../aggregates/aggregate-distinct-1.out            |    2 +-
 4 files changed, 19 insertions(+), 5 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-expression.vala b/src/libtracker-data/tracker-sparql-expression.vala
index 49b49e5..824495b 100644
--- a/src/libtracker-data/tracker-sparql-expression.vala
+++ b/src/libtracker-data/tracker-sparql-expression.vala
@@ -246,7 +246,6 @@ class Tracker.Sparql.Expression : Object {
 	static void convert_expression_to_string (StringBuilder sql, PropertyType type, long begin) {
 		switch (type) {
 		case PropertyType.STRING:
-		case PropertyType.INTEGER:
 			// nothing to convert
 			break;
 		case PropertyType.RESOURCE:
diff --git a/src/libtracker-data/tracker-sparql-pattern.vala b/src/libtracker-data/tracker-sparql-pattern.vala
index da907ab..9080678 100644
--- a/src/libtracker-data/tracker-sparql-pattern.vala
+++ b/src/libtracker-data/tracker-sparql-pattern.vala
@@ -659,6 +659,7 @@ class Tracker.Sparql.Pattern : Object {
 		foreach (var variable in triple_context.variables) {
 			bool maybe_null = true;
 			bool in_simple_optional = false;
+			PropertyType last_type = PropertyType.UNKNOWN;
 			string last_name = null;
 			foreach (VariableBinding binding in triple_context.var_bindings.lookup (variable).list) {
 				string name;
@@ -669,6 +670,7 @@ class Tracker.Sparql.Pattern : Object {
 					// always first in loop as variable is required to be unbound
 					name = variable.sql_expression;
 				}
+				var type = binding.data_type;
 				if (last_name != null) {
 					if (!first_where) {
 						sql.append (" AND ");
@@ -676,11 +678,23 @@ class Tracker.Sparql.Pattern : Object {
 						sql.append (" WHERE ");
 						first_where = false;
 					}
-					sql.append (last_name);
+
+					if (last_type == PropertyType.STRING && type == PropertyType.RESOURCE) {
+						sql.append_printf ("(SELECT ID FROM Resource WHERE Uri = %s)", last_name);
+					} else {
+						sql.append (last_name);
+					}
+
 					sql.append (" = ");
-					sql.append (name);
+
+					if (last_type == PropertyType.RESOURCE && type == PropertyType.STRING) {
+						sql.append_printf ("(SELECT ID FROM Resource WHERE Uri = %s)", name);
+					} else {
+						sql.append (name);
+					}
 				}
 				last_name = name;
+				last_type = type;
 				if (!binding.maybe_null) {
 					maybe_null = false;
 				}
@@ -1409,6 +1423,7 @@ class Tracker.Sparql.Pattern : Object {
 					}
 				} else {
 					// variable as predicate
+					binding.data_type = PropertyType.STRING;
 					binding.sql_db_column_name = "object";
 					binding.maybe_null = true;
 				}
diff --git a/tests/libtracker-data/aggregates/aggregate-1.out b/tests/libtracker-data/aggregates/aggregate-1.out
index 702d22b..8ea62e7 100644
--- a/tests/libtracker-data/aggregates/aggregate-1.out
+++ b/tests/libtracker-data/aggregates/aggregate-1.out
@@ -1 +1 @@
-"9"	"3.333333"	"5"	"1"
+"9"	"3.33333333333333"	"5"	"1"
diff --git a/tests/libtracker-data/aggregates/aggregate-distinct-1.out b/tests/libtracker-data/aggregates/aggregate-distinct-1.out
index 5d49fe0..e5cb99d 100644
--- a/tests/libtracker-data/aggregates/aggregate-distinct-1.out
+++ b/tests/libtracker-data/aggregates/aggregate-distinct-1.out
@@ -1 +1 @@
-"3.333333"	"4.000000"
+"3.33333333333333"	"4.0"