Strange SQLAlchemy error message: TypeError: 'dict' object does not support indexing

Question

I am using hand crafted SQL to fetch data from a PG database, using SqlAlchemy. I am trying a query which contains the SQL like operator \'%\' and that seems to throw SqlAlc

Answer 1

Another way of solving your problem, if you don't want to escape % characters or use sqlalchemy.text(), is to use a regular expression.

Instead of:

select id from ref_geog where short_name LIKE '%opt'

Try (for case-sensitive match):

select id from ref_geog where short_name ~ 'opt$' 

or (for case-insensitive):

select id from ref_geog where short_name ~* 'opt$'

Both LIKE and regex are covered in the documentation on pattern matching.

Note that:

Unlike LIKE patterns, a regular expression is allowed to match anywhere within a string, unless the regular expression is explicitly anchored to the beginning or end of the string.

For an anchor, you can use the assertion $ for end of string (or ^ for beginning).

Answer 2

You have to give %% to use it as % because % in python is use as string formatting so when you write single % its assume that you are going to replace some value with this.

So when you want to place single % in string with query allways place double %.

Answer 3

This could also result from the case - in case parameters to be passed onto the SQL are declared in DICT formate and are being manipulated in the SQL in the form of LIST or TUPPLE.

Answer 4

It seems like your problem may be related to this bug.

In which case, you should triple-escape as a workaround.

Answer 5

SQLAlchemy has a text() function for wrapping text which appears to correctly escape the SQL for you.

I.e.

res = executeSql(sqlalchemy.text(sql))

should work for you and save you from having to do the manual escaping.

Answer 6

I found one more case when this error shows up:

c.execute("SELECT * FROM t WHERE a = %s")

In other words, if you provide parameter (%s) in query, but you forget to add query params. In this case error message is very misleading.