Lecture presented at IIUG 2016, mainly directed to developers, but with several good practices from user cases, and suggested solutions and approaches.

1. Alexandre Marini
Senior IT Consultant
Brazil
Don't make your Informix static -
developers do's and don'ts tips

2. Don't make your Informix static - developers do's and don'ts
tips
 - Simple code changes can make a huge
impact
 - Some “don'ts” specific cases
 - How to use UDFs in SQL
 - Tips for generic development / work
Agenda

3. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
1) Choose a right data type/validation method
Create table [tabname]
(col1 integer,
col2 char(14),
col3 varchar(50),
col4 char(14),
primary key (cod1)
);
Columns 2 and 4 stores two kinds of records: personal or company ID,
depending on char length.

4. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
- Validation UDR was running in procedure – isnumeric() based
- Going through all 14/11 digits for != [0-9]
- Running into a big table (around 320 K rows)
- 2 columns (cols 2 and 4)
- Data loading procedure: obviously as fast as a turtle!
- Simple line of cast turned the process 89% faster
ge: Col2::decimal(14,0)

5. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
2) Verify your search patterns
Example: An ITIN, or Individual Taxpayer Identification Number, 9-digit
length, beginning with the number "9", formatted like an SSN (NNN-
NN-NNNN).
- searches with like %chars%, or matches *chars*, in an alpha
column with a pattern on the first “n” digits
select count(nmr_lancto)
from recconta
where cdg_fornecedor like "%01838723%" and dat_cancel is null
and nmr_or is null and dat_recebto is null

6. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
- using like '%[digits]%', the cost is very high
- note that used indexes are the same: before and after changes
Estimated Cost: 13476
Estimated # of Rows Returned: 1
1) informix.recconta: INDEX PATH
(1) Index Name: informix.xie12recconta
Index Keys: dat_cancel nmr_or dat_recebto cdg_fornecedor (Key-First) (Serial,
fragments: ALL)
Lower Index Filter: ((informix.recconta.dat_recebto IS NULL AND
informix.recconta.nmr_or IS NULL ) AND informix.recconta.dat_cancel IS NULL )
Index Key Filters: (informix.recconta.cdg_fornecedor LIKE '%01838723%' )

7. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
- rewritten query, just with like '[digits]%', (same begin
pattern)…
select count(nmr_lancto)
from recconta
where cdg_fornecedor like "01838723%" and
dat_cancel is null and nmr_or is null and dat_recebto is null
Estimated Cost: 79
Estimated # of Rows Returned: 1
1) informix.recconta: INDEX PATH
(1) Index Name: informix.xie12recconta
Index Keys: dat_cancel nmr_or dat_recebto cdg_fornecedor (Serial, fragments: ALL)
Lower Index Filter: (((informix.recconta.cdg_fornecedor LIKE '01838723%' AND
informix.recconta.dat_recebto IS NULL ) AND informix.recconta.nmr_or IS NULL ) AND
informix.recconta.dat_cancel IS NULL

8. Don't make your Informix static - developers do's and don'ts
tips

Simple code changes can make a huge impact
3) Be careful with trigger events – audit trigger example
ORIGINAL CODE:
CREATE TRIGGER [trigger_name] UPDATE on [table_name]
REFERENCING OLD AS o NEW AS n
for each row
if o.column1 != n.column2 then
insert into tbaudit_upd(values…)
end if
end;
RECOMMENDED CODE:
CREATE TRIGGER [trigger_name] UPDATE OF [audit_field] on [table_name]
REFERENCING OLD as o NEW AS n
for each row
WHEN n.column1 != o.column1
insert into tbaudit_upd(values….);
End;
- Focus on the most specific trigger event
Benefits: lower processing avoiding unecessary executions!

9. Don't make your Informix static - developers do's and don'ts
tips

Some don'ts specific cases
- Avoid DISTINCT, unless extremely needed:
Prefer cleaning and normalizing data, create constraints at the fields,
before insert triggers…
- Avoid *s:
 - define clauses: define abc record like [table].*
 - selects, deletes, into clauses
 - updates: update [table] set [table.]* = record.*
 - inserts clauses without column names
 insert into [table] values (record.*)

A simple schema change, with one added column, will demand lots of
code changing! Time is money!

10. Don't make your Informix static - developers do's and don'ts
tips
- Avoid using UDFs in WHERE sections

SELECT 'Email sent: ' || email_subject || ' from ' ||
UPPER(email_from) || ' to ' || UPPER(email_to) || ' at ' ||
email_datetime
FROM USU_EMAIL
WHERE UPPER(email_from) =
'ALEXANDRE@MCSOFTWARE.COM.BR'
Estimated Cost: 326
Estimated # of Rows Returned: 500
1) usu_email: SEQUENTIAL SCAN
Filters: UPPER(usu_email.email_from ) =
'ALEXANDRE@MCSOFTWARE.COM.BR
How to use UDFs in SQL

11. Don't make your Informix static - developers do's and don'ts
tips

How to use UDFs in SQL
- Two possibilities:
1) Normalize data before input
2) Create a functional index
CREATE FUNCTION toUpper(name VARCHAR(100))
RETURNS VARCHAR(100) WITH (NOT
VARIANT);
RETURN upper( name );
END FUNCTION;
CREATE INDEX idx_upper_email ON USU_EMAIL
( toUpper(email_from) );

12. Don't make your Informix static - developers do's and don'ts
tips

How to use UDFs in SQL
- Running the same query again:
SELECT 'Email sent: ' || email_subject || ' from ' ||
UPPER(email_from) || ' to ' || UPPER(email_to) || ' at ' || email_datetime
FROM USU_EMAIL
WHERE UPPER(email_from) = `ALEXANDRE@MCSOFTWARE.COM.BR'
Estimated Cost: 2
Estimated # of Rows Returned: 2
1) usu_email: INDEX PATH
(1) Index Name: idx_upper_email
Index Keys: toupper(email_de) (Serial, fragments: ALL)
Lower Index Filter: toupper(usu_email.email_de)=
`ALEXANDRE@MCSOFTWARE.COM.BR'
 UDRs are shown in sqexplain output:
 UDRs in query:
--------------
UDR id : 454
UDR name: toupper

13. Don't make your Informix static - developers do's and don'ts
tips

Tips for generic development / work
- Simplifying (KISS), Reuse, Documenting


 - Don't try to reinvent the wheel. Database
manager systems have UDRs to do whatever you
need


 - Work together with your DBA. He must be
boring, but he can save your time, brains, and
provide you several tech tips

14. Don't make your Informix static - developers do's and don'ts
tips

Questions?
alexandre@mcsoftware.com.br