Join Two Big Tables Fast - oracle

Question

after research via playing with the queries and doing online research, I am turning to you for input. Looking forward to your replies! I am trying to write this in a general way as I am looking for general ideas on how to do this, not for exact statements. If this question is received poorly, I am happy to rework it, let me know. Here we go:
I have two tables:
Table 1 has 10 MIO records. It has only one column:
Column A: A unique ID (a text e.g. '5uz1g09aksmsd')
Table 2 has 300 MIO records. It has two columns:
Column A: A unique ID (a text e.g. '5uz1g09aksmsd')
Column B: A number (e.g. 32.5432)
There are no indices etc. yet, not even a PK as both tables have just been created via CTAS. Both tables have been analysed.
I am now looking for a fast query (the prep-work e.g. index creation can take time, no problem) to create a third table that contains the 10 MIO rows of Table 1, and Column B of Table 2 if a match is found via Column A (for 99% a match will be found). To make it clearer, a simple CTAS could be:
create table3 as
select t1.a,
(select t2.b from table2 t2 where t2.a = t1.a and rownum = 1)
-- the rownum = 1 is to show Oracle that there can only be one match
from table1 t1;
This is not as fast as it can be (I hope). What are your ideas to make it faster? Creating indices? Which ones? What kind of join would you want to see in the execution plan? A hash join? I already found
create table nologging
parallel query execution and parallel table creation
But I am interested in the specifics of how the perfect execution plan for this would look given that we are allowed to alter the system (e.g. create an index). In particular I am asking for 11gR2 but 12c comments are also very welcome.

Answer 1

Start with the simplest possibility using this query
create table c as
select /*+ parallel(6) */ a.a, b.b
from a
left outer join b
on a.a = b.a
;
It will use a hash join, adjust parallel degree based on your hardware setup.
The expected execution plan is as follows
--------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------------------------
| 0 | CREATE TABLE STATEMENT | | 261M| 6238M| 56799 (1)| 00:03:48 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10002 | 261M| 6238M| 31984 (1)| 00:02:08 | Q1,02 | P->S | QC (RAND) |
| 3 | LOAD AS SELECT | C | | | | | Q1,02 | PCWP | |
|* 4 | HASH JOIN OUTER | | 261M| 6238M| 31984 (1)| 00:02:08 | Q1,02 | PCWP | |
| 5 | PX RECEIVE | | 7849K| 44M| 726 (1)| 00:00:03 | Q1,02 | PCWP | |
| 6 | PX SEND HASH | :TQ10000 | 7849K| 44M| 726 (1)| 00:00:03 | Q1,00 | P->P | HASH |
| 7 | PX BLOCK ITERATOR | | 7849K| 44M| 726 (1)| 00:00:03 | Q1,00 | PCWC | |
| 8 | TABLE ACCESS STORAGE FULL| A | 7849K| 44M| 726 (1)| 00:00:03 | Q1,00 | PCWP | |
| 9 | PX RECEIVE | | 261M| 4741M| 31149 (1)| 00:02:05 | Q1,02 | PCWP | |
| 10 | PX SEND HASH | :TQ10001 | 261M| 4741M| 31149 (1)| 00:02:05 | Q1,01 | P->P | HASH |
| 11 | PX BLOCK ITERATOR | | 261M| 4741M| 31149 (1)| 00:02:05 | Q1,01 | PCWC | |
| 12 | TABLE ACCESS STORAGE FULL| B | 261M| 4741M| 31149 (1)| 00:02:05 | Q1,01 | PCWP | |
--------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("A"."A"="B"."A"(+))
My test with synthetic data of your size is 35 seconds.