shramov / tll-odbc

ODBC writer channel for TLL

ODBC Channel for TLL framework

Channel implements read and write operations using ODBC API for flat messages - no lists, submessages or unions.

For example channel with url odbc://;dsn=testdb;quote-mode=sqlite will connect to testdb ODBC database (specified either in user config ~/.odbc.ini or in global one /etc/odbc.ini) with sqlite quoting mode.

Name quoting

Number of table and field name quoting methods are supported:

• sqlite: quote with backticks as `table`;
• psql: quote with double qoutes as "table";
• sybase: quote with square brackets as [table];

Method is selected with quote-mode channel parameter.

Statement templates

SQL statements are built on channel open from message options. Statement can be either write-only (insert or procedure call) or read-write (function call or raw query), where sql.output: message-name controls what messages are filled from result dataset. Possible templates (sql.template message option) are:

• none - don't create any statement;
• insert - insert statement of form INSERT INTO {table}(i0, i1, ...) VALUES ?, ?, ...;
• function - select of form SELECT o0, o1, ... FROM {func}(?, ?, ...), or if function-mode=empty is given - SELECT FROM {func}(?, ?, ...);
• procedure - call of form CALL {func}(?, ?, ...);

Message sequence (msg.seq) number is implicitly included in dataset as _tll_seq field but can be excluded with sql.with-seq: no option.

Example of function call, where Input initiates call and generates bunch of Output messages with swapped fields:

- name: Input
  options.sql.table: TestFunction
  options.sql.output: Output
  options.sql.template: function
  options.sql.with-seq: no
  id: 10
  fields:
    - {name: a, type: int32}
    - {name: b, type: double}
- name: Output
  options.sql.with-seq: no
  options.sql.template: none
  id: 20
  fields:
    - {name: a, type: double}
    - {name: b, type: int32}

Selecting data

There is no template for select statements - it would be either very limited or needs lot of options to provide enough functionality. Two ways to query data are implemented:

• dynamic queries using Query control message
• writing raw query in message sql.query option

Example of prepared SELECT statement, where data is stored in table Table with Insert and queried with Select messages (providing stream of Insert).

- name: Insert
  options.sql.table: Table
  id: 10
  fields:
    - {name: f0, type: int32}
    - {name: f1, type: double}

- name: Select
  options.sql.with-seq: no
  options.sql.query: 'SELECT "_tll_seq", "f0", "f1" FROM "Table" WHERE "f0" < ?'
  options.sql.output: Insert
  id: 20
  fields:
    - {name: upper_bound, type: int32}