* refactor: Replace ctx.Done() with ctx.Err()
Prior to this commit we checked for context cancellation with a select
block and context.Context.Done() without multiplexing over any other
channel like:
select {
case <-ctx.Done():
// handle cancellation
default:
// fallthrough
}
This commit replaces those type of blocks with a simple check of
ctx.Err(). This has the following benefits:
* Calling ctx.Err() is much faster than entering a select block.
* ctx.Done() allocates a channel when called for the first time.
* Testing the result of ctx.Err() is a reliable way of determininging if
a context.Context value has been canceled.
* fix: Fix data race in execDeleteTagValueEntry()
Any operation between an int64 and uint64 results in the type becoming a
uint64. This is because the most common will usually be an unsigned
cursor being modified by an int literal. Even in cases where we were to
add an unsigned literal to an integer iterator, that would just result
in it being recast back and overflow.
When using `SHOW MEASUREMENTS ON <db>`, the required permissions didn't
take into account `<db>` and would only use the `db` parameters from the
HTTP parameters.
When an integer cannot be parsed, we attempt to parse it as a uint64. If
that succeeds, we then have an unsigned literal that can then be used to
compare unsigned values.
This method allows us not to introduce new syntax to the language and
continue just doing the right thing at the right time. But, it also
delegates a lot of the heavy lifting to implicit casting in Reduce and
Eval.
All time ranges are combined with AND regardless of context and
regardless of whether it makes any logical sense.
That was the previous behavior and, unfortunately, a lot of people rely
on it.
This is used quite a bit to determine which fields are needed in a
condition. When the condition gets large, the memory usage begins to
slow it down considerably and it doesn't take care of duplicates.
There are several places in the code where comma-ok map retrieval was
being used poorly. Some were benign, like checking existence before
issuing an unconditional delete with no cleanup. Others were potentially
far more serious: assuming that if 'ok' was true, then the resulting
pointer retrieved from the map would be non-nil. `nil` is a perfectly
valid value to store in a map of pointers, and the comma-ok syntax is
meant for when membership is distinct from having a non-zero value.
There was only one or two cases that I saw that being used correctly for
maps of pointers.
This refactors the validation code so it is more flexible and performs a
small bit of work to make preparing and executing the query easier.
The general idea is that compilation will eventually do more heavy
lifting in creating the initial plan and prepare will construct an
actual plan rather than just doing some basic field rewriting.
This change at least sets us up for that change in the future and moves
the validation code to the query execution instead of in the parser.
This also frees up the parser to parse the complete AST without worrying
if the query itself is valid. That could be useful for client code that
wants to compile a partial query to an AST and then perform
modifications on the AST for some reason.
The statement rewriting logic should be in the query engine as part of
preparing a query. This creates a shard mapper interface that the query
engine expects and then passes it to the query engine instead of
requiring the query to be preprocessed before being input into the query
engine. This interface is (mostly) the same as the old interface, just
moved to a different package.
The ConditionExpr function is more accurate because it parses the
condition and ensures that time conditions are actually used correctly.
That means that attempting to combine conditions with OR will not result
in the query silently pretending it's an AND and nested conditions work
correctly so there is only one way to read the query.
It also extracts the non-time conditions into a separate condition so we
can stop attempting to parse around the time conditions in lower layers
of the storage engine. This change does not remove those hacks, but a
following commit should be able to sanitize the condition and remove
them.
This change provides a clear separation between the query engine
mechanics and the query language so that the language can be parsed and
dealt with separate from the query engine itself.
Previously pseudo iterators could be created for meta data such
as series, measurement, and tag data. These iterators were created
at a higher level and lacked a lot of the power of the query engine.
This commit moves system iterators down to the series level and
supports the following:
- _name
- _seriesKey
- _tagKey
- _tagValue
- _fieldKey
These can be used as normal fields such as:
SELECT _seriesKey FROM cpu
This will return all the series keys for `cpu`.
Ayan George
Brett Buddin
Stuart Carnie
Edd Robinson
Andrew Hare
Jonathan A. Sternberg
Joe LeGasse
Ben Johnson