AnalyticDB for PostgreSQL:Use MaxCompute foreign tables to access MaxCompute data

The MaxCompute FDW module allows you to synchronize data between AnalyticDB for PostgreSQL and MaxCompute. You can create the following types of MaxCompute foreign tables by using MaxCompute FDW:

• Non-partitioned foreign tables, which are mapped to non-partitioned MaxCompute tables.

• Last-level partitioned foreign tables, which are mapped to the last-level partitions of partitioned MaxCompute tables.

• Partitioned foreign tables, which are mapped to partitioned MaxCompute tables.

• For a new AnalyticDB for PostgreSQL instance, the MaxCompute FDW extension is automatically created. In this case, you can skip the preceding steps.

• For an existing AnalyticDB for PostgreSQL instance, you can use the privileged database account to connect to a specific database, run the preceding commands to create the MaxCompute FDW extension, and then grant permissions on the extension to all database accounts.

Before you use a MaxCompute foreign table, you must perform the following operations:

• Create a MaxCompute server to specify the endpoint for accessing MaxCompute.

• Create a MaxCompute user mapping to specify the account that can access the created MaxCompute server.

• Create a MaxCompute foreign table to specify the MaxCompute table that you want to access.

1.1 Sample code

CREATE SERVER odps_serv                        -- The name of the MaxCompute server.
  FOREIGN DATA WRAPPER odps_fdw
  OPTIONS (
    tunnel_endpoint '<odps tunnel endpoint>'   -- The endpoint of the MaxCompute Tunnel service.
  );

1.2 Options

When you create a MaxCompute server in AnalyticDB for PostgreSQL, you need to specify only one of the tunnel_endpoint and odps_endpoint options. The following table describes the options.

For more information about MaxCompute endpoints, see Endpoints.

2.1 Sample code

CREATE USER MAPPING FOR { username | USER | CURRENT_USER | PUBLIC }
  SERVER odps_serv                                  -- The name of the MaxCompute server.
  OPTIONS (
    id '<odps access id>',                                -- The AccessKey ID of the account used to access the MaxCompute server.
    key '<odps access key>'                               --  The AccessKey secret of the account used to access the MaxCompute server.
  );

2.2 Options

When you create an AnalyticDB for PostgreSQL database account that is used to access the MaxCompute server, specify the type, AccessKey ID, and AccessKey secret of the account.

3.1 Sample code

CREATE FOREIGN TABLE IF NOT EXISTS table_name ( -- The name of the MaxCompute foreign table.
    column_name data_type [, ... ]
)
  SERVER odps_serv                              -- The name of the MaxCompute server.
  OPTIONS (
    project '<odps project>',                   -- The name of the MaxCompute project.
    table '<odps table>'                        -- The name of the MaxCompute table.
);

3.2 Options

After you create a MaxCompute server and a user mapping to the MaxCompute server, you can create a MaxCompute foreign table. The following table describes the options.

3.3 Types of foreign tables

MaxCompute FDW allows you to create the following types of MaxCompute foreign tables based on the types of MaxCompute tables:

• Non-partitioned foreign tables

  A non-partitioned foreign table is mapped to a non-partitioned MaxCompute table. When you create a non-partitioned foreign table, you need to specify valid values only for the project and table options. You do not need to specify the partition option, or you can leave the partition option empty. Example:

  CREATE FOREIGN TABLE odps_lineitem (              -- The name of the MaxCompute foreign table.
      l_orderkey      bigint,
      l_partkey       bigint,
      l_suppkey       bigint,
      l_linenumber    bigint,
      l_quantity      double precision,
      l_extendedprice double precision,
      l_discount      double precision,
      l_tax           double precision,
      l_returnflag    char(1),
      l_linestatus    char(1),
      l_shipdate      date,
      l_commitdate    date,
      l_receiptdate   date,
      l_shipinstruct  char(25),
      l_shipmode      char(10),
      l_comment       varchar(44)
  ) SERVER odps_serv                              -- The name of the MaxCompute server.
  OPTIONS (
    project 'odps_fdw',                           -- The name of the MaxCompute project.
    table 'lineitem_big'                          -- The name of the MaxCompute table.
  );

• Last-level partitioned foreign tables

  A last-level partitioned foreign table is mapped to a last-level partition of a MaxCompute table. When you create a last-level partitioned foreign table, you must specify valid values for the partition option. If a MaxCompute table is partitioned at multiple levels, you can map the last-level partitioned foreign table only to a last-level partition of the MaxCompute table. You must set the partition option to the full path of the last-level partition.

  In the following example, a partitioned table that contains two levels of partitions in MaxCompute is created:

  -- Create a partitioned table that contains two levels of partitions. In the partitioned table, pt is used as a level-1 partition key column and region is used as a level-2 partition key column.
  CREATE TABLE src (key string, value bigint) PARTITIONED BY (pt string,region string);

  

  For example, a MaxCompute table is partitioned at two levels and contains the 20170601 partition and the hangzhou subpartition. To create a last-level partitioned foreign table that is mapped to the hangzhou subpartition in an AnalyticDB for PostgreSQL database, the partition option must be set to pt=20170601,region=hangzhou.

  CREATE FOREIGN TABLE odps_src_20170601_hangzhou (   -- The name of the MaxCompute foreign table.
    key string,
    value bigint
  ) SERVER odps_serv                                  -- The name of the MaxCompute server.
  OPTIONS (
    project 'odps_fdw',                               -- The name of the MaxCompute project. 
    table 'src',                                      -- The name of the MaxCompute table.
    partition 'pt=20170601,region=hangzhou'           -- The full path of the last-level partition.
  );

  Note

  • Set the partition option in the key=value format. To specify a last-level partition in a multi-level partitioned table, separate the key-value pairs with commas (,). Do not include spaces in the partition option.

  • You cannot map a last-level partitioned foreign table to a non-last-level partition of a MaxCompute table. In this example, you cannot set the partition option to pt=20170601, which specifies the path of the partition.

  • Make sure that you set the partition option to the full path of a last-level partition. In this example, you cannot set the partition option to

    region=hangzhou, which specifies the relative path of the last-level partition.

• Partitioned foreign tables

  A partitioned foreign table is mapped to a partitioned MaxCompute table. The following code shows how to use the preceding MaxCompute table named src that contains two levels of partitions to create a partitioned foreign table. For more information, see Define table partitioning.

  CREATE FOREIGN TABLE odps_src(                    -- The name of the MaxCompute foreign table.
    key text,
    value bigint,
    pt text,                                        -- The partition key of the MaxCompute foreign table.
    region text                                     -- The subpartition key of the MaxCompute foreign table.
  ) SERVER odps_serv
  OPTIONS (
    project 'odps_fdw',                             -- The name of the MaxCompute project.
    table 'src'                                     -- The name of the partitioned MaxCompute table.
  )
  PARTITION BY LIST (pt)                            -- Use the pt field to partition the table.
  SUBPARTITION BY LIST (region)                     -- Use the region field to subpartition the table.
      SUBPARTITION TEMPLATE (                       -- Specify a subpartition template.
         SUBPARTITION hangzhou VALUES ('hangzhou'),
         SUBPARTITION shanghai VALUES ('shanghai')
      )
  ( PARTITION "20170601" VALUES ('20170601'), 
    PARTITION "20170602" VALUES ('20170602'));

  Note

  When you create a partitioned foreign table in an AnalyticDB for PostgreSQL database, make sure that the following requirements are met. The requirements differ from the requirements for creating partitioned tables in MaxCompute.

  • Append the partition keys as fields to the end of other fields. If you create a multi-level partitioned foreign table, make sure that the order and level of partition keys and the partition levels of the MaxCompute table match one another.

  • When you create a partitioned table, you must specify the partition key values. To partition a table, use the LIST method.

  • When you create a partitioned foreign table, you do not need to specify the partition option. If you specify the partition option, the foreign table is created based on the specified last-level partition of the specified MaxCompute table instead of the whole MaxCompute table.

  • If a partitioned foreign table contains partitions or subpartitions that have no matches in the specified MaxCompute table, an alert is triggered when you query the foreign table. In this case, you can delete the corresponding partition or subpartition from the foreign table. For more information, see the "Delete partitions or subpartitions from a partitioned foreign table" section in this topic.

    

3.4 Add partitions or subpartitions to a partitioned foreign table

In this example, the preceding partitioned foreign table named odps_src is used.

• Add a partition, as shown in the following figure.

-- Add a partition. The subpartitions are automatically created.
alter table odps_src add partition "20170603" values(20170603);

• Add a subpartition, as shown in the following figure.

-- Add a subpartition.
alter table odps_src alter partition "20170603" add partition "nanjing" values('nanjing');

3.5 Delete partitions or subpartitions from a partitioned foreign table

In this example, the preceding partitioned foreign table named odps_src is used.

• Delete a partition, as shown in the following figure.

-- Delete a partition. The cascaded subpartitions are also deleted.
alter table odps_src drop partition "20170602";

• Delete a subpartition, as shown in the following figure.

-- Delete a subpartition.
alter table odps_src alter partition "20170601" drop partition "hangzhou";

The following table describes the data type mappings between MaxCompute and AnalyticDB for PostgreSQL. We recommend that you specify the data types of columns in a foreign table in an AnalyticDB for PostgreSQL database based on the listed mappings.

You can execute foreign scans on AnalyticDB for PostgreSQL databases to scan MaxCompute foreign tables. You can execute the same query statements to query data in foreign tables and data in other tables in AnalyticDB for PostgreSQL. In this example, TPC Benchmark™H (TPC-H) queries are used to illustrate common scenarios in which MaxCompute foreign tables are used.

TPC-H Q1 queries are used to aggregate and filter data in a single table. In this example, a Q1 query is performed on the MaxCompute foreign table named odps_lineitem.

-- Create the MaxCompute foreign table named odps_lineitem.
CREATE FOREIGN TABLE odps_lineitem (
    l_orderkey bigint,
    l_partkey bigint,
    l_suppkey bigint,
    l_linenumber bigint,
    l_quantity double precision,
    l_extendedprice double precision,
    l_discount double precision,
    l_tax double precision,
    l_returnflag CHAR(1),
    l_linestatus CHAR(1),
    l_shipdate DATE,
    l_commitdate DATE,
    l_receiptdate DATE,
    l_shipinstruct CHAR(25),
    l_shipmode CHAR(10),
    l_comment VARCHAR(44)
) server odps_serv
    options (
        project 'odps_fdw', table 'lineitem'
    );

-- TPC-H Q1
select
    l_returnflag,
    l_linestatus,
    sum(l_quantity) as sum_qty,
    sum(l_extendedprice) as sum_base_price,
    sum(l_extendedprice * (1 - l_discount)) as sum_disc_price,
    sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge,
    avg(l_quantity) as avg_qty,
    avg(l_extendedprice) as avg_price,
    avg(l_discount) as avg_disc,
    count(*) as count_order
from
    odps_lineitem
where
    l_shipdate <= date '1998-12-01' - interval '88' day --(3)
group by
    l_returnflag,
    l_linestatus
order by
    l_returnflag,
    l_linestatus;

To import data, perform the following steps:

1. Create a MaxCompute foreign table in an AnalyticDB for PostgreSQL database.

2. To import data to the new table, execute one of the following statements:

-- INSERT statement
INSERT INTO <Destination on-premises table> SELECT * FROM <MaxCompute foreign table>;

-- CREATE TABLE AS statement
CREATE TABLE <Destination on-premises table> AS SELECT * FROM <MaxCompute foreign table>;

• Example 1: Execute the INSERT statement to import the data in odps_lineitem to an on-premises append-optimized column-oriented storage (AOCS) table.

-- Create an on-premises AOCS table.
CREATE TABLE aocs_lineitem (
    l_orderkey bigint,
    l_partkey bigint,
    l_suppkey bigint,
    l_linenumber bigint,
    l_quantity double precision,
    l_extendedprice double precision,
    l_discount double precision,
    l_tax double precision,
    l_returnflag CHAR(1),
    l_linestatus CHAR(1),
    l_shipdate DATE,
    l_commitdate DATE,
    l_receiptdate DATE,
    l_shipinstruct CHAR(25),
    l_shipmode CHAR(10),
    l_comment VARCHAR(44)
) WITH (APPENDONLY=TRUE, ORIENTATION=COLUMN, COMPRESSTYPE=ZSTD, COMPRESSLEVEL=5)
DISTRIBUTED BY (l_orderkey);

-- Import the data in odps_lineitem_orc to the on-premises AOCS table.
INSERT INTO aocs_lineitem SELECT * FROM odps_lineitem;

• Example 2: Execute the CREATE TABLE AS statement to import the data in odps_lineitem to an on-premises heap table.

create table heap_lineitem as select * from odps_lineitem distributed by (l_orderkey);

In this example, a TPC-H Q19 query is performed on the MaxCompute foreign table named odps_part that is associated with the on-premises AOCS table named aocs_lineitem.

-- TPC-H Q19
select
    sum(l_extendedprice* (1 - l_discount)) as revenue
from
    aocs_lineitem,          -- The name of the on-premises AOCS table.
    odps_part               -- The name of the MaxCompute foreign table.
where
    (
        p_partkey = l_partkey
        and p_brand = 'Brand#32'
        and p_container in ('SM CASE', 'SM BOX', 'SM PACK', 'SM PKG')
        and l_quantity >= 8 and l_quantity <= 8 + 10
        and p_size between 1 and 5
        and l_shipmode in ('AIR', 'AIR REG')
        and l_shipinstruct = 'DELIVER IN PERSON'
    )
    or
    (
        p_partkey = l_partkey
        and p_brand = 'Brand#41'
        and p_container in ('MED BAG', 'MED BOX', 'MED PKG', 'MED PACK')
        and l_quantity >= 15 and l_quantity <= 15 + 10
        and p_size between 1 and 10
        and l_shipmode in ('AIR', 'AIR REG')
        and l_shipinstruct = 'DELIVER IN PERSON'
    )
    or
    (
        p_partkey = l_partkey
        and p_brand = 'Brand#44'
        and p_container in ('LG CASE', 'LG BOX', 'LG PACK', 'LG PKG')
        and l_quantity >= 22 and l_quantity <= 22 + 10
        and p_size between 1 and 15
        and l_shipmode in ('AIR', 'AIR REG')
        and l_shipinstruct = 'DELIVER IN PERSON'
    );