Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Igal @ Lucee.org]

On 11/9/2017 8:19 AM, Merlin Moncure wrote:

On Thu, Nov 9, 2017 at 8:22 AM, Adam Brusselback
 wrote:

Since you are migrating data into a staging table in PostgreSQL, you may set
the field data type as TEXT for each field where you have noticed or
anticipate issues.
Then after population perform the datatype transformation query on the given
fields to determine the actual field value that could not be gracefully
transformed.

This is the approach I have come to as the most successful for data migrations.

I will use tools like Kettle / Talend to get data into a staging table
with every column as text, then use SQL to migrate that to a properly
typed table.  Works much better than trying to work within the
constraints of these tools.

YES

I call the approach 'ELT', (Extract, Load, Trasform).  You are much
better off writing transformations in SQL than inside of an ETL tool.
This is a perfect example of why.


All sound advice.  Thanks.


Igal Sapir

Lucee Core Developer
Lucee.org 

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Merlin Moncure]

On Thu, Nov 9, 2017 at 8:22 AM, Adam Brusselback
 wrote:
>> Since you are migrating data into a staging table in PostgreSQL, you may set
>> the field data type as TEXT for each field where you have noticed or
>> anticipate issues.
>> Then after population perform the datatype transformation query on the given
>> fields to determine the actual field value that could not be gracefully
>> transformed.
>
> This is the approach I have come to as the most successful for data 
> migrations.
>
> I will use tools like Kettle / Talend to get data into a staging table
> with every column as text, then use SQL to migrate that to a properly
> typed table.  Works much better than trying to work within the
> constraints of these tools.

YES

I call the approach 'ELT', (Extract, Load, Trasform).  You are much
better off writing transformations in SQL than inside of an ETL tool.
This is a perfect example of why.

merlin


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Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Adam Brusselback]

> Since you are migrating data into a staging table in PostgreSQL, you may set
> the field data type as TEXT for each field where you have noticed or
> anticipate issues.
> Then after population perform the datatype transformation query on the given
> fields to determine the actual field value that could not be gracefully
> transformed.

This is the approach I have come to as the most successful for data migrations.

I will use tools like Kettle / Talend to get data into a staging table
with every column as text, then use SQL to migrate that to a properly
typed table.  Works much better than trying to work within the
constraints of these tools.


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Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Allan Kamau]

On Thu, Nov 9, 2017 at 9:58 AM, Igal @ Lucee.org  wrote:

> On 11/8/2017 6:25 PM, Igal @ Lucee.org wrote:
>
>> On 11/8/2017 5:27 PM, Allan Kamau wrote:
>>
>>> Maybe using NUMERIC without explicitly stating the precision is
>>> recommended. This would allow for values with many decimal places to be
>>> accepted without truncation. Your field may need to capture very small
>>> values such as those in bitcoin trading or some banking fee or interest.
>>>
>>
>> That's a very good idea.  For some reason I thought that I tried that
>> earlier and it didn't work as expected, but I just tested it (again?) and
>> it seems to work well, so that's what I'll do.
>>
>
> Another weird thing that I noticed:
>
> On another column, "total_charged", that was migrated properly as a
> `money` type, when I run `sum(total_charged::money)` I get `null`, but if I
> cast it to numeric, i.e. `sum(total_charged::numeric)`, I get the expected
> sum result.
>
> Is there a logical explanation to that?
>
>
> Igal
>
>
>
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>

Since you are migrating data into a staging table in PostgreSQL, you may
set the field data type as TEXT for each field where you have noticed or
anticipate issues.
Then after population perform the datatype transformation query on the
given fields to determine the actual field value that could not be
gracefully transformed.
For example
SELECT a.* FROM . a WHERE
a.::NUMERIC IS NULL LIMIT 10;


or to identify values not within the expected range, substitute the place
holders in the query below with appropriate values and issue the query.

SELECT a.* FROM . a WHERE NOT
a.::NUMERIC BETWEEN
 AND  LIMIT 10;


Once you have determined the issues and solved them. Construct a second
table having similar field names but more restrictive (correct) data types
such as NUMERIC where appropriate. The insert into this table the data from
the staging table. Your insertion query would have the data casting clauses.


Allan.

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Igal @ Lucee.org]

On 11/8/2017 6:25 PM, Igal @ Lucee.org wrote:

On 11/8/2017 5:27 PM, Allan Kamau wrote:
Maybe using NUMERIC without explicitly stating the precision is 
recommended. This would allow for values with many decimal places to 
be accepted without truncation. Your field may need to capture very 
small values such as those in bitcoin trading or some banking fee or 
interest.


That's a very good idea.  For some reason I thought that I tried that 
earlier and it didn't work as expected, but I just tested it (again?) 
and it seems to work well, so that's what I'll do.


Another weird thing that I noticed:

On another column, "total_charged", that was migrated properly as a 
`money` type, when I run `sum(total_charged::money)` I get `null`, but 
if I cast it to numeric, i.e. `sum(total_charged::numeric)`, I get the 
expected sum result.


Is there a logical explanation to that?


Igal


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Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Igal @ Lucee.org]

On 11/8/2017 5:27 PM, Allan Kamau wrote:
Maybe using NUMERIC without explicitly stating the precision is 
recommended. This would allow for values with many decimal places to 
be accepted without truncation. Your field may need to capture very 
small values such as those in bitcoin trading or some banking fee or 
interest.


That's a very good idea.  For some reason I thought that I tried that 
earlier and it didn't work as expected, but I just tested it (again?) 
and it seems to work well, so that's what I'll do.


Thank you,

Igal Sapir
Lucee Core Developer
Lucee.org 

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Allan Kamau]

On Nov 9, 2017 04:12, "Igal @ Lucee.org"  wrote:

Thank you all for your help:


On 11/8/2017 4:45 PM, Tom Lane wrote:

"Igal @ Lucee.org"   writes:

The value in the offending insert is:  0.0

Why does Postgres decide that 0.0 is "double precision" (which is a
weird name in my opinion -- why can't it just be double) and not money?

Kettle must be telling it that --- on its own, PG would think '0.0'
is numeric, which it does have a cast to money for.


Looks like you are correct.  Kettle shows me the INSERT statement and when
I execute it outside of Kettle (in a regular SQL client), the INSERT
succeeds.

On 11/8/2017 4:45 PM, David G. Johnston wrote:

The lack of quotes surrounding the value is significant.  Money input
requires a string literal.  Only (more or less) integer and double literal
values can be written without the single quotes.


That didn't work.  I CAST'ed the value in the SELECT to VARCHAR(16) but all
it did was change the error message to say that it expected `money` but
received `character varying`.

On 11/8/2017 4:52 PM, Allan Kamau wrote:

 On Nov 9, 2017 03:46, "Tom Lane" 

Maybe using NUMERIC without explicitly stating the precision is
recommended. This would allow for values with many decimal places to be
accepted without truncation. Your field may need to capture very small
values such as those in bitcoin trading or some banking fee or interest.

Allan.

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Igal @ Lucee.org]

Thank you all for your help:

On 11/8/2017 4:45 PM, Tom Lane wrote:

"Igal @ Lucee.org"  writes:

The value in the offending insert is:  0.0

Why does Postgres decide that 0.0 is "double precision" (which is a
weird name in my opinion -- why can't it just be double) and not money?

Kettle must be telling it that --- on its own, PG would think '0.0'
is numeric, which it does have a cast to money for.


Looks like you are correct.  Kettle shows me the INSERT statement and 
when I execute it outside of Kettle (in a regular SQL client), the 
INSERT succeeds.


On 11/8/2017 4:45 PM, David G. Johnston wrote:

The lack of quotes surrounding the value is significant.  Money input 
requires a string literal.  Only (more or less) integer and double 
literal values can be written without the single quotes.


That didn't work.  I CAST'ed the value in the SELECT to VARCHAR(16) but 
all it did was change the error message to say that it expected `money` 
but received `character varying`.


On 11/8/2017 4:52 PM, Allan Kamau wrote:


 On Nov 9, 2017 03:46, "Tom Lane" 

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Allan Kamau]

On Nov 9, 2017 03:46, "Tom Lane"  wrote:

"Igal @ Lucee.org"  writes:
> I have a column named "discount" of type money in SQL Server.  I created
> the table in Postgres with the same name and type, since Postgres has a
> type named money, and am transferring the data by using PDI (Pentaho
> Data Integration) Kettle/Spoon.

> Kettle throws an error though:  column "discount" is of type money but
> expression is of type double precision.

> The value in the offending insert is:  0.0

> Why does Postgres decide that 0.0 is "double precision" (which is a
> weird name in my opinion -- why can't it just be double) and not money?

Kettle must be telling it that --- on its own, PG would think '0.0'
is numeric, which it does have a cast to money for.

regression=# create table m (m1 money);
CREATE TABLE
regression=# insert into m values (0.0);
INSERT 0 1
regression=# insert into m values (0.0::numeric);
INSERT 0 1
regression=# insert into m values (0.0::float8);
ERROR:  column "m1" is of type money but expression is of type double
precision
LINE 1: insert into m values (0.0::float8);
  ^
HINT:  You will need to rewrite or cast the expression.

You'll need to look at the client-side code to see where it's going wrong.

> The only solution I found is to set the column in Postgres to DOUBLE
> PRECISION instead of MONEY, but I'm not sure if there are negative side
> effects to that?

Well, it's imprecise.  Most people don't like that when it comes to
monetary amounts.

regards, tom lane


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Could try using NUMERIC datatype for such a field.

Allan

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[David G. Johnston]

On Wednesday, November 8, 2017, Igal @ Lucee.org  wrote:
>
> Kettle throws an error though:  column "discount" is of type money but
> expression is of type double precision.
>
> The value in the offending insert is:  0.0
>
> Why does Postgres decide that 0.0 is "double precision" (which is a weird
> name in my opinion -- why can't it just be double) and not money?
>
The lack of quotes surrounding the value is significant.  Money input
requires a string literal.  Only (more or less) integer and double literal
values can be written without the single quotes.

David J.

Re: [GENERAL] Migrating money column from MS SQL Server to Postgres

[Tom Lane]

"Igal @ Lucee.org"  writes:
> I have a column named "discount" of type money in SQL Server.  I created 
> the table in Postgres with the same name and type, since Postgres has a 
> type named money, and am transferring the data by using PDI (Pentaho 
> Data Integration) Kettle/Spoon.

> Kettle throws an error though:  column "discount" is of type money but 
> expression is of type double precision.

> The value in the offending insert is:  0.0

> Why does Postgres decide that 0.0 is "double precision" (which is a 
> weird name in my opinion -- why can't it just be double) and not money?

Kettle must be telling it that --- on its own, PG would think '0.0'
is numeric, which it does have a cast to money for.

regression=# create table m (m1 money);
CREATE TABLE
regression=# insert into m values (0.0);
INSERT 0 1
regression=# insert into m values (0.0::numeric);
INSERT 0 1
regression=# insert into m values (0.0::float8);
ERROR:  column "m1" is of type money but expression is of type double precision
LINE 1: insert into m values (0.0::float8);
  ^
HINT:  You will need to rewrite or cast the expression.

You'll need to look at the client-side code to see where it's going wrong.

> The only solution I found is to set the column in Postgres to DOUBLE 
> PRECISION instead of MONEY, but I'm not sure if there are negative side 
> effects to that?

Well, it's imprecise.  Most people don't like that when it comes to
monetary amounts.

regards, tom lane


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