Best practices for PySpark programming
History of SQL and all the advanced features over the last 30 years among big vendors.
Credits to: Peter James Thomas:
- Not establishing a dedicated team. The team never escapes from “the day job” or legacy / BAU issues; the past prevents the future from being built.
- Staff lack skills and prior experience of data programmes. Sub-optimal functionality, slippages, later performance problems, higher ongoing support costs. Time is also wasted educating people rather than getting on with work.
- Not establishing an appropriate management / governance structure. The programme is not aligned with business needs, is not able to get necessary time with business users and cannot negotiate the inevitable obstacles that block its way.
- Poor programme management. The programme loses direction. Time is expended on non-core issues. Milestones are missed. Expenditure escalates beyond budget.
- Big Bang approach. Too much time goes by without any value being created. The eventual Big Bang is instead a damp squib. Large sums of money are spent without any benefits.
- Lack of focus on interim deliverables. Business units become frustrated and seek alternative ways to meet their pressing needs. This leads to greater fragmentation and reputational damage to the programme.
- Insufficient time spent understanding source system data and how data is transformed as it flows between systems. This leads to data capabilities that do not reflect business transactions with fidelity. There is inconsistency with reports directly drawn from source systems. Reconciliation issues arise.
- Not enough up-front focus on understanding key business decisions and the information necessary to take them. Analytic capabilities do not focus on what people want or need, leading to poor adoption and benefits not being achieved.
- Lack of leverage of new data capabilities in front-end / digital systems. These systems are less effective. The data team is jealous about its own approved capabilities being the only way that users should get information, rather than adopting a more pragmatic and value-added approach.
- Education is an afterthought, training is technology- rather than business-focused. People neither understand the capabilities of new analytical tools, nor how to use them to derive business value. Again this leads to poor adoption and little return on investment.
Most companies don’t realize the effort involved in Business Intelligence. Often they just throw semi-technical business analysts at a problem instead of committing dedicated technical resources to Data Management and Analytics Reporting.
Taken from a Dataiku meetup slide. This picture hit close to home.
I switched to wordpress.com as my host. I will most likely switch to AWS later.
Redshift is based off branch of PostGreSQL 8.0.2 [ PostgreSQL 8.0.2 was released in 2005]
here’s all the unsupported fancy PostGres Stuff: taken directly from amazon’s manual.
The bigs ones are: No Store Procedures, No Constraints enforcement, No triggers and no table functions, no upserts.
However, don’t ever forget that for an Amazon Redshift query can do:
Select count(disinct column_name) from table.
200x faster than PostGres on a Billion row table.
Unsupported PostgreSQL Features
These PostgreSQL features are not supported in Amazon Redshift.
Do not assume that the semantics of elements that Amazon Redshift and PostgreSQL have in common are identical. Make sure to consult the Amazon Redshift Developer Guide SQL Commands to understand the often subtle differences.
- Only the 8.x version of the PostgreSQL query tool psql is supported.
- Table partitioning (range and list partitioning)
- Foreign key
- Primary key
- Check constraints
- Exclusion constraints
Unique, primary key, and foreign key constraints are permitted, but they are informational only. They are not enforced by the system, but they are used by the query planner.
- Postgres system columnsAmazon Redshift SQL does not implicitly define system columns. However, the PostgreSQL system column names cannot be used as names of user-defined columns. See http://www.postgresql.org/docs/8.0/static/ddl-system-columns.html
- NULLS clause in Window functions
- CollationsAmazon Redshift does not support locale-specific or user-defined collation sequences. See Collation Sequences.
- Value expressions
- Subscripted expressions
- Array constructors
- Row constructors
- Stored procedures
- Management of External Data (SQL/MED)
- Table functions
- VALUES list used as constant tables
- Recursive common table expressions
- Full text search