[teiid-issues] [JBoss JIRA] (TEIID-2138) PG DSN for for ODBC metadata query LIKE issues

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749304#comment-12749304 ] 

Steven Hawkins commented on TEIID-2138:
---------------------------------------

Based upon https://community.jboss.org/message/784457 also added one more change to 8.3 so that the system property change is not needed out of the box.  If a like is specified using an E'' string literal pattern and no escape is specified we'll assume \ - since E escaping is not generally documented and considered specific to pg support this is not considered a breaking change.
                
> PG DSN for for ODBC metadata query LIKE issues
> ----------------------------------------------
>
>                 Key: TEIID-2138
>                 URL: https://issues.jboss.org/browse/TEIID-2138
>             Project: Teiid
>          Issue Type: Quality Risk
>          Components: ODBC, Query Engine
>    Affects Versions: 7.7
>            Reporter: Johnathon Lee
>            Assignee: Steven Hawkins
>             Fix For: 8.2
>
>
> Various clients (Cognos, Excel, DBVisualizer) exhibit different results when querying metadata.
> For instance:
> Querying ModeShape on a fresh 5.3 deploy.
> {code}
> select relname from pg_catalog.pg_class c, pg_catalog.pg_namespace n where relname like E'ddl\\_alterable' and n.oid = relnamespace
> {code}
>   0 Records
> {code}
> select relname from pg_catalog.pg_class c, pg_catalog.pg_namespace n where relname like E'ddl_alterable' and n.oid = relnamespace
> {code}
>   1 Record:  ddl_alterable
> {code}
> select relname from pg_catalog.pg_class c, pg_catalog.pg_namespace n where relname like E'ddl\_alterab__' and n.oid = relnamespace
> {code}
>   1 Record:  ddl_alterable
> Looking at [1] per [2].  It seems proper escaping of the E'literal' syntax is not always being performed.  The Third example above shows that a wildcard is being escaped and happens to match to a literal value it expects.
> [1]
> PostgreSQL also accepts "escape" string constants, which are an extension to the SQL standard. An escape string constant is specified by writing the letter E (upper or lower case) just before the opening single quote, e.g. E'foo'. (When continuing an escape string constant across lines, write E only before the first opening quote.) Within an escape string, a backslash character (\) begins a C-like backslash escape sequence, in which the combination of backslash and following character(s) represents a special byte value. \b is a backspace, \f is a form feed, \n is a newline, \r is a carriage return, \t is a tab. Also supported are \digits, where digits represents an octal byte value, and \xhexdigits, where hexdigits represents a hexadecimal byte value. (It is your responsibility that the byte sequences you create are valid characters in the server character set encoding.) Any other character following a backslash is taken literally. Thus, to include a backslash character, write two backslashes (\\). Also, a single quote can be included in an escape string by writing \', in addition to the normal way of ''.
> [2]  http://www.postgresql.org/docs/8.3/interactive/sql-syntax-lexical.html#SQL-SYNTAX-STRINGS

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