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create_function: impossible to call set_error #164
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rangeroob
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Apr 11, 2020
Added tests to demonstrate three issues with the way sqlite3-ruby currently handles aggregate functions: (1) Defining a second aggregate function and using both results in memory violation. The problem is that `rb_iv_set(self, "@agregator", aggregator);` (database.c:399) just overwrites the last reference to the first AggregateHandler, but SQLite still holds a pointer to it and will follow the pointer if the first aggregate function is used in a query. The most straight-forward fix is to insert the aggregator in a ruby array and never release it -- similar to how its done for functions. (2) Using the same aggregate function twice in a query mixes up values from both columns. For example: `SELECT MYAGGREG(a), MYAGGREG(b) FROM foo;` Leads to: Myaggreg.step(a1); Myaggreg.step(b1); Myaggreg.step(a2); Myaggreg.step(b2); ... ; Myaggreg.finalize(), Myaggreg.finalize() The SQLite API expects the caller to differentiate between these chains of invocation via `sqlite3_aggregate_context()`, but current sqlite3-ruby does not account for that. #44 has been a work around for this in the special case that the first aggregation is finalized before the second started (separate queries). sparklemotion#161 does the analog for the function Proxy. (3) Documentation implies that library users shall explicitly set the arity of the function. Consequently the library user is likely to expect that this is passed down to SQLite, so he may define multiple functions with the same name but different arity and SQLite to use the most appropriate one (documented sqlite feature). Unfortunately, sqlite3-ruby does not pass the arity to SQLite, which is surprising given that different arity-values are accounted for in the C code. The problem is that sqlite3-ruby does not call the AggregateHandlers "arity" method but instead queries the arity of the "step" method from Ruby (sqlite3_obj_method_arity). Confusingly, this is not the "step" provided by the library user, but the "step" of the Proxy Wrapper classes introduced by Database.create_aggregate or Database.create_aggregate_handler. Both of these are just `step(*args)`, so the arity reported to SQLite is always -1. Things not addressed: - sparklemotion#164 impossible to call FunctionProxy.set_error (and FunctionProxy.count). because @driver does not exist (anymore) - Database.create_aggregate and the tests contain a 'text_rep' field, that is never passed down to SQLite. It is not advertised in the documentation, though. (cherry picked from commit ae89dea)
alexcwatt
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Mar 1, 2024
This code depends on a SQLite API which is deprecated, sqlite3_aggregate_count. In addition, the present implementation is broken (@driver is always nil). Related: sparklemotion#164.
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FunctionProxy#set_error is implemented like this:
it looks that the instance variable
@driver
is never set, which causes the following error:database.rb:559:in
set_error': undefined methodresult_error' for nil:NilClass (NoMethodError)
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