Extraction Queries for Amazon Redshift¶

Alation Cloud Service Applies to Alation Cloud Service instances of Alation

Customer Managed Applies to customer-managed instances of Alation

Query-based extraction allows users to customize metadata extraction down to the level of specific metadata objects, such as tables, columns, views, and others by using custom queries.

Table, column, view, and function definition metadata types are enabled by default, and users cannot disable them.

By default, the following additional metadata types are enabled, but can be disabled by users:

Primary keys

Foreign keys

Functions

Users can disable the metadata types that are not required by clearing the corresponding checkboxes.

System schemas are disabled by default. Users can enable their extraction if required.

To use this feature, you will need to write custom queries to extract specific metadata. Alation expects that these queries conform to a required structure and use the expected reserved identifiers. Sections below contain the expected query structure for each metadata type.

Catalog¶

Make sure that your query has a column labeled as CATALOG in the SELECT list.

Example:

SELECT
            distinct CURRENT_DATABASE() AS CATALOG
    FROM
            PG_NAMESPACE
    WHERE
            lower(nspname) NOT LIKE  'pg_%%'
            AND lower(nspname) NOT IN   ( 'information_schema')
            AND lower(nspname)  NOT IN ('''');

Schema¶

Make sure that your query has a column labeled as CATALOG, SCHEMA in the SELECT list.

Example:

SELECT
        CURRENT_DATABASE() AS CATALOG,
        nspname AS SCHEMA
FROM
        PG_NAMESPACE
WHERE
        lower(nspname) NOT LIKE  'pg_%%'
        AND lower(nspname) NOT IN   ( 'information_schema')
        AND lower(nspname)  NOT IN ('''');

Table¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, TABLE_NAME, TABLE_OWNER ``, ``TABLE_TYPE, and REMARKS in the SELECT list.

Example:

SELECT
        *
FROM
        (
        SELECT
                CURRENT_DATABASE() AS CATALOG,
                A.SCHEMA AS SCHEMA,
                A.TABLE_NAME,
                A.TABLE_OWNER,
                A.TABLE_TYPE,
                pgd.description AS REMARKS
        FROM
                (
                SELECT
                        T.SCHEMANAME AS SCHEMA,
                        T.TABLENAME AS TABLE_NAME,
                        T.TABLEOWNER AS TABLE_OWNER,
                        'TABLE' AS TABLE_TYPE
                FROM
                        PG_TABLES T
        UNION
                SELECT
                        V.SCHEMANAME AS SCHEMA,
                        V.VIEWNAME AS VIEW_NAME,
                        V.VIEWOWNER AS TABLE_OWNER,
                        'VIEW' AS TABLE_TYPE
                FROM
                        PG_VIEWS V ) A
        LEFT JOIN PG_CATALOG.pg_statio_all_tables c on
                (c.relname = A.table_name
                and c.schemaname = A.SCHEMA)
        LEFT JOIN PG_CATALOG.pg_description pgd on
                (pgd.objoid = c.relid)
        WHERE
                A.SCHEMA NOT IN (
                SELECT
                        schemaname
                from
                        svv_external_schemas)
                AND lower(A.SCHEMA) NOT LIKE  'pg_%%'
                AND (pgd.objsubid = 0)
UNION
        SELECT
                CATALOG,
                SCHEMA,
                TABLE_NAME,
                TABLE_OWNER,
                TABLE_TYPE,
                REMARKS
        from
                (
                SELECT
                        CURRENT_DATABASE() AS CATALOG,
                        A.SCHEMA as SCHEMA,
                        A.TABLE_NAME as TABLE_NAME,
                        A.TABLE_OWNER as TABLE_OWNER,
                        A.TABLE_TYPE as TABLE_TYPE,
                        null AS REMARKS,
                        pgd.objoid as objoid
                FROM
                        (
                        SELECT
                                T.SCHEMANAME AS SCHEMA,
                                T.TABLENAME AS TABLE_NAME,
                                T.TABLEOWNER AS TABLE_OWNER,
                                'TABLE' AS TABLE_TYPE
                        FROM
                                PG_TABLES T
                UNION
                        SELECT
                                V.SCHEMANAME AS SCHEMA,
                                V.VIEWNAME AS VIEW_NAME,
                                V.VIEWOWNER AS TABLE_OWNER,
                                'VIEW' AS TABLE_TYPE
                        FROM
                                PG_VIEWS V ) A
                LEFT JOIN PG_CATALOG.pg_statio_all_tables c on
                        (c.relname = A.table_name
                        and c.schemaname = A.SCHEMA)
                LEFT JOIN PG_CATALOG.pg_description pgd on
                        (pgd.objoid = c.relid)
                WHERE
                        A.SCHEMA NOT IN (
                        SELECT
                                schemaname
                        from
                                svv_external_schemas)
                        AND lower(A.SCHEMA) NOT LIKE  'pg_%%' ) tt
        where
                not exists(
                select
                        1
                from
                        PG_CATALOG.pg_description pt
                where
                        pt.objoid = tt.objoid
                        and pt.objsubid = 0)
UNION
        SELECT
                CURRENT_DATABASE() AS CATALOG,
                A.schemaname AS SCHEMA,
                A.tablename AS TABLE_NAME,
                null as TABLE_OWNER,
                'TABLE' as TABLE_TYPE,
                null as REMARKS
        from
                SVV_EXTERNAL_TABLES A
        join svv_external_schemas B on
                A.schemaname = B.schemaname )
WHERE
        lower(SCHEMA) NOT IN   ( 'information_schema')
        AND lower(SCHEMA) NOT IN ('''')
AND TABLE_TYPE != 'VIEW';

View¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, VIEW_NAME, VIEW_CREATE_STATEMENT, 'VIEW' AS VIEW_TYPE, and REMARKS in the SELECT list.

Example:

SELECT
  CURRENT_DATABASE() AS CATALOG,
  schemaname AS SCHEMA,
  viewname AS VIEW_NAME,
  CASE
          WHEN lower(substring(definition,1,100)) like 'create materialized view%' THEN definition
          WHEN lower(substring(definition,1,100)) like 'create or replace materialized view%' THEN definition
          WHEN lower(substring(definition,1,100)) like 'create view%' THEN definition
          WHEN lower(substring(definition,1,100)) like 'create or replace view%' THEN definition
  ELSE 'CREATE OR REPLACE VIEW ' || SCHEMA || '.' || VIEW_NAME || ' AS ' || definition
  END AS VIEW_CREATE_STATEMENT,
  'VIEW' AS VIEW_TYPE,
  VIEWOWNER AS TABLE_OWNER,
  null AS REMARKS
FROM
  PG_VIEWS
WHERE
  lower(schemaname) NOT LIKE 'pg_%%'
  AND lower(schemaname) NOT IN ('information_schema')
  AND lower(schemaname) NOT IN ('''');

Column¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, TABLE_NAME, TYPE_NAME, DATA_TYPE, COLUMN_NAME, ORDINAL_POSITION, IS_NULLABLE, REMARKS, and COLUMN_DEFAULT in the SELECT list.

Example:

SELECT
  table_catalog AS CATALOG,
  table_schema AS SCHEMA,
  table_name,
  column_name,
  data_type,
  CASE
          WHEN data_type = 'character varying' THEN 'varchar'
          WHEN data_type = 'timestamp without time zone' THEN 'timestamp'
          WHEN data_type = 'timestamp with time zone' THEN 'timestamptz'
          WHEN data_type = 'double precision' THEN 'FLOAT'
          ELSE data_type
  END as type_name,
  CASE
          WHEN data_type = 'character varying' THEN character_maximum_length
          WHEN data_type = 'numeric' THEN numeric_precision
          WHEN data_type = 'character' THEN character_maximum_length
          ELSE -1
  END AS length,
  numeric_scale,
  ordinal_position,
  is_nullable,
  column_default,
  remarks
FROM
  svv_columns
WHERE
  lower(SCHEMA) NOT LIKE 'pg_%%'
  AND lower(SCHEMA) NOT IN ('information_schema')
  AND lower(SCHEMA) NOT IN ('''');

Primary Key¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, TABLE_NAME, COLUMN_NAME and KEY_SEQ in the SELECT list.

Example:

SELECT
  CURRENT_DATABASE() AS CATALOG,
  S.NSPNAME AS SCHEMA,
  C.RELNAME AS TABLE_NAME,
  CONSTR.CONNAME AS PK_NAME,
  ATTR.ATTNAME AS COLUMN_NAME,
  ATTR.ATTNUM AS KEY_SEQ
FROM
  PG_CONSTRAINT CONSTR
INNER JOIN PG_ATTRIBUTE ATTR ON
  ATTR.ATTNUM = ANY (CONSTR.CONKEY)
  AND ATTR.ATTRELID = CONSTR.CONRELID
INNER JOIN PG_CLASS C ON
  CONSTR.CONRELID = C.OID
INNER JOIN PG_NAMESPACE S ON
  C.RELNAMESPACE = S.OID
WHERE
  lower(S.NSPNAME) NOT LIKE 'pg_%%'
  AND lower(S.NSPNAME) NOT IN ('''')
  AND lower(S.NSPNAME) NOT IN ('information_schema')
  AND CONSTR.CONTYPE = 'p';

Foreign Key¶

Make sure that your query has columns labeled as PK_CATALOG, PK_SCHEMA, PK_TABLE, PK_COLUMN, FK_CATALOG, FK_SCHEMA, FK_TABLE, and FK_COLUMN in the SELECT list.

Example:

SELECT
  CURRENT_DATABASE() AS FK_CATALOG,
  CURRENT_DATABASE() AS PK_CATALOG,
  F.FKTABLE_SCHEM AS FK_SCHEMA,
  F.FKTABLE_NAME AS FK_TABLE,
  F.FK_NAME,
  F.FKCOLUMN_NAME AS FK_COLUMN,
  F.KEY_SEQ,
  P.PKTABLE_SCHEM AS PK_SCHEMA,
  P.PKTABLE_NAME AS PK_TABLE,
  P.PK_NAME,
  P.PKCOLUMN_NAME AS PK_COLUMN
FROM
  (
  SELECT
          S.NSPNAME AS FKTABLE_SCHEM,
          C.RELNAME AS FKTABLE_NAME,
          CONSTR.CONNAME AS FK_NAME,
          ATTR.ATTNAME AS FKCOLUMN_NAME,
          ATTR.ATTNUM AS KEY_SEQ,
          CONSTR.CONFKEY,
          CONSTR.CONFRELID
  FROM
          PG_CONSTRAINT CONSTR
  INNER JOIN PG_ATTRIBUTE ATTR ON
          ATTR.ATTNUM = ANY (CONSTR.CONKEY)
          AND ATTR.ATTRELID = CONSTR.CONRELID
  INNER JOIN PG_CLASS C ON
          CONSTR.CONRELID = C.OID
  INNER JOIN PG_NAMESPACE S ON
          C.RELNAMESPACE = S.OID
          AND CONSTR.CONTYPE = 'f'
  WHERE
          lower(S.NSPNAME) NOT LIKE 'pg_%%'
          AND lower(S.NSPNAME) NOT IN ('''')
          AND lower(S.NSPNAME) NOT IN ( 'information_schema')
 ) F
INNER JOIN (
  SELECT
          S.NSPNAME AS PKTABLE_SCHEM,
          C.RELNAME AS PKTABLE_NAME,
          CONSTR.CONNAME AS PK_NAME,
          ATTR.ATTNAME AS PKCOLUMN_NAME,
          ATTR.ATTNUM AS PKEY_SEQ,
          C.OID
  FROM
          PG_CONSTRAINT CONSTR
  INNER JOIN PG_ATTRIBUTE ATTR ON
          ATTR.ATTNUM = ANY (CONSTR.CONKEY)
          AND ATTR.ATTRELID = CONSTR.CONRELID
  INNER JOIN PG_CLASS C ON
          CONSTR.CONRELID = C.OID
  INNER JOIN PG_NAMESPACE S ON
          C.RELNAMESPACE = S.OID
          AND CONSTR.CONTYPE = 'p'
  WHERE
          lower(S.NSPNAME) NOT LIKE 'pg_%%'
          AND lower(S.NSPNAME) NOT IN ('''')
          AND lower(S.NSPNAME) NOT IN ( 'information_schema')
 ) P ON
  P.PKEY_SEQ = ANY (F.CONFKEY)
  AND P.OID = F.CONFRELID;

Function¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, FUNCTION_NAME, and REMARKS in the SELECT list.

Example:

SELECT
  CURRENT_DATABASE() AS CATALOG,
  S.NSPNAME AS SCHEMA,
  P.PRONAME AS FUNCTION_NAME,
          P.PROSRC AS FUNCTION_DEFINITION,
  NULL AS SPECIFIC_NAME,
  NULL AS REMARKS
FROM
  PG_PROC P
INNER JOIN PG_NAMESPACE S ON
  P.PRONAMESPACE = S.OID
INNER JOIN PG_LANGUAGE L ON
  P.PROLANG = L.OID
WHERE
  (L.LANNAME IN ('internal', 'sql')
  AND p.prorettype <> 'pg_catalog.trigger'::pg_catalog.regtype
  OR L.LANNAME IN ('plpythonu'))
  AND lower(S.NSPNAME) NOT IN ('''')
  AND lower(S.NSPNAME) NOT LIKE 'pg_%%'
  AND lower(S.NSPNAME) NOT IN ( 'information_schema');

Function Definition¶

Make sure that your query has columns labeled as CATALOG, SCHEMA, FUNCTION_NAME, ARG_NAME, TYPE_NAME, ARG_TYPE, and ARG_DEF in the SELECT list.

Example:

SELECT
  CURRENT_DATABASE() AS CATALOG,
  N.NSPNAME AS SCHEMA,
  P.PRONAME AS FUNCTION_NAME,
  ISNULL(P.PROARGNAMES,'{}') AS ARG_NAME,
  P.PRONARGS AS NUM_OF_FUNCTION_ARGS,
  ISNULL(STRING_TO_ARRAY(REPLACE(OIDVECTORTYPES(P.PROARGTYPES), '\"', ''), ','),'{}') AS ARG_TYPE,
  FORMAT_TYPE(P.PRORETTYPE, NULL) AS TYPE_NAME,
  P.PROSRC AS ARG_DEF
FROM
  PG_PROC P
INNER JOIN PG_NAMESPACE N ON
  P.PRONAMESPACE = N.OID
INNER JOIN PG_LANGUAGE L ON
  P.PROLANG = L.OID
WHERE
  (L.LANNAME IN ('internal',
  'sql')
  AND p.prorettype <> 'pg_catalog.trigger'::pg_catalog.regtype
  OR L.LANNAME IN ('plpythonu'))
  AND lower(N.NSPNAME) NOT IN ('''')
  AND lower(N.NSPNAME) NOT LIKE 'pg_%%'
  AND lower(N.NSPNAME) NOT IN ('information_schema');

Extraction Queries for Amazon Redshift¶

Catalog¶

Schema¶

Table¶

View¶

Column¶

Primary Key¶

Foreign Key¶

Function¶

Function Definition¶

Alation User Documentation PDFs