2. Mateusz Herych
Android Developer - Base CRM
Co-organizer - GDG Krakow
Co-organizer - KrakDroid

3. Stats

4. LIKE ‘%smth%’

5. LIKE ‘%smth%’
is not the way.

6. Search

7. Search
Offline.

8. Why?

9. Why?
Let the backend guys do the job

10. Why?
Internet is not everywhere.

11. Why?
Internet is not everywhere.
It takes time. (especially SSL)

12. Why?
Internet is not everywhere.
It takes time. (especially SSL)
And sometimes it’s shitty.

13. Why?
Internet is not everywhere.
It takes time. (especially SSL)
And sometimes it’s shitty.

14. Sure, some apps don’
t really need it
You need an Internet to order
that taxi anyway

15. Do you keep offline
content?
Let your users navigate fast.

16. Did I say fast?

17. How?
Let’s go deeper.

18. Context

19. CRM
- Contacts
- Deals
- Notes
- ...

20. CRM
- Contacts (~100)
- Deals (~50)
- Notes (~100)
- ...2011

21. select id from deals where name LIKE ‘%
something%’

22. CRM
- Contacts (~40K)
- Deals (~20K)
- Notes (~300K)
- ...

24. HOW DOES “LIKE” WORKS
LIKE?

25. Docs saying

26. I tried to put all the
conditions that need to be
satisfied so SQLite can use
indices combined with LIKE
operator.
Docs saying

27. They didn’t fit.
Docs saying

28. http://www.sqlite.
org/optoverview.html
Docs saying

29. Hey, you, SQLite!
EXPLAIN (my) QUERY PLAN

30. PRAGMA case_sensitive_like=1;

31. PRAGMA case_sensitive_like=1;
CREATE INDEX search_index on deals(name);

32. PRAGMA case_sensitive_like=1;
CREATE INDEX search_index on deals(name);
SELECT id FROM deals WHERE name LIKE
‘Some%’;

33. EXPLAIN QUERY PLAN
SELECT id FROM deals WHERE
name LIKE ‘Some%’;
SEARCH TABLE deals USING COVERING
INDEX search_index (name>? AND name<?)
(~31250 rows)

34. EXPLAIN QUERY PLAN
SELECT id FROM deals WHERE
name LIKE ‘%Some%’;

35. EXPLAIN QUERY PLAN
SELECT id FROM deals WHERE
name LIKE ‘%Some%’;
SCAN TABLE deals (~500000 rows)

36. EXPLAIN QUERY PLAN
SELECT id FROM deals WHERE
name LIKE ‘%Some%’;
SCAN TABLE deals (~500000 rows)
(And then you die)

37. first_name || ‘ ‘ || last_name?
complicated queries, VIEWs?
Like is NOT the way
to go.

38. What people think SQLite is

39. What SQLite really is

40. SQLite is
powerful
Not kidding.

41. FTS3
Full Text Search

42. CREATE VIRTUAL TABLE
search USING fts3 (tokens)

43. ?
CREATE VIRTUAL TABLE
search USING fts3 (tokens INT)

44. Nope.
PRAGMA table_info(search);
cid|name|type|notnull|dflt_value|pk
0|word||0||0

45. All is TEXT, except for hidden
rowid.

46. What is virtual table?
Imagine it’s a Java interface.
interface VirtualTable {
void insert(Params p);
void update(Params p);
// etc, also createTable.
}

47. What is a virtual table?
class Fts3 implements VirtualTable {
// …
}

49. MATCH
Let’s go make some magic.

50. SELECT * FROM search WHERE
content MATCH ‘something’

51. SELECT rowid, * FROM search
WHERE content MATCH
‘something’
rowid|word
1|something
2|not something special
3|SoMeThInG

52. SELECT rowid, * FROM search
WHERE content
MATCH ‘some* spe*’
rowid|word
2|not something special

53. CREATE VIRTUAL TABLE
search USING fts3 (author, lyrics)

54. SELECT * FROM search WHERE
lyrics
MATCH ‘author:Giorgio Synthesizer
author |lyrics
Giorgio Moroder|..Why don’t I use a
synthesizer...

55. Cool?

56. Cool?
Look at this.

57. SELECT * FROM search WHERE
lyrics
MATCH ‘why NEAR synthesizer’
author |lyrics
Giorgio Moroder|..Why don’t I use
synthesizer...

58. SELECT * FROM search WHERE
lyrics
MATCH ‘why NEAR/3 synthesizer’
author |lyrics
Giorgio Moroder|..Why don’t I use
synthesizer...

59. Tips.

60. 1. Your FTS vtable should contain
only tokens. Divided into sections.

61. 2. Link your FTS table’s records
with other table (containing real
object’s id and type) using rowid.

62. 3. Remember. FTS is fast enough
for searching purposes. But it’s
always slower than ‘=’ based query
on indexed field.

63. 4. EXPLAIN QUERY PLAN doesn’t
work for fts tables. Try to measure
it with .timer ON.

64. 5. ???

65. 6. QUESTIONS TIME!