go-mysql-server is a SQL engine which parses standard SQL (based on MySQL syntax) and executes queries on data sources of your choice. A simple in-memory database and table implementation are provided, and you can query any data source you want by implementing a few interfaces.
go-mysql-server also provides a server implementation compatible with the MySQL wire protocol. That means it is compatible with MySQL ODBC, JDBC, or the default MySQL client shell interface.
These are the goals of go-mysql-server:
- Be a generic extensible SQL engine that performs queries on your data sources.
- Provide a simple database implementation suitable for use in tests.
- Define interfaces you can implement to query your own data sources.
- Provide a runnable server speaking the MySQL wire protocol, connected to data sources of your choice.
- Optimize query plans.
- Allow implementators to add their own analysis steps and optimizations.
- Support indexed lookups and joins on data tables that support them.
- Support external index driver implementations such as pilosa.
- With few caveats and using a full database implementation, be a drop-in MySQL database replacement.
Non-goals of go-mysql-server:
- Be an application/server you can use directly.
- Provide any kind of backend implementation (other than the
memory
one used for testing) such as json, csv, yaml. That's for clients to implement and use.
What's the use case of go-mysql-server?
go-mysql-server has two primary uses case:
-
Stand-in for MySQL in a golang test environment, using the built-in
memory
database implementation. -
Providing access to aribtrary data sources with SQL queries by implementing a handful of interfaces. The most complete real-world implementation is Dolt.
The import path for the package is github.com/dolthub/go-mysql-server
.
To install it, run:
go get github.com/dolthub/go-mysql-server
The goal of go-mysql-server is to support 100% of the statements that MySQL does. We are continuously adding more functionality to the engine, but not everything is supported yet. To see what is currently included check the SUPPORTED file.
We support and actively test against certain third-party clients to ensure compatibility between them and go-mysql-server. You can check out the list of supported third party clients in the SUPPORTED_CLIENTS file along with some examples on how to connect to go-mysql-server using them.
Name | Description |
---|---|
ABS(expr) |
returns the absolute value of an expression |
ACOS(expr) |
returns the arccos of an expression |
ARRAY_LENGTH(json) |
if the json representation is an array, this function returns its size. |
ASIN(expr) |
returns the arcsin of an expression |
ATAN(expr) |
returs the arctan of an expression |
AVG(expr) |
returns the average value of expr in all rows. |
CEIL(number) |
returns the smallest integer value that is greater than or equal to number . |
CEILING(number) |
returns the smallest integer value that is greater than or equal to number . |
CHARACTER_LENGTH(str) |
returns the length of the string in characters. |
CHAR_LENGTH(str) |
returns the length of the string in characters. |
COALESCE(...) |
returns the first non-null value in a list. |
CONCAT(...) |
concatenates any group of fields into a single string. |
CONCAT_WS(sep, ...) |
concatenates any group of fields into a single string. The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL. |
CONNECTION_ID() |
returns the current connection ID. |
COS(expr) |
returns the cosine of an expression. |
COT(expr) |
returns the arctangent of an expression. |
COUNT(expr) |
returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. |
CURRENT_USER() |
returns the current user |
DATE(date) |
returns the date part of the given date . |
DATETIME(expr) |
returns a DATETIME value for the expression given (e.g. the string '2020-01-02'). |
DATE_ADD(date, interval) |
adds the interval to the given date . |
DATE_SUB(date, interval) |
subtracts the interval from the given date . |
DAY(date) |
is a synonym for DAYOFMONTH(). |
DAYOFMONTH(date) |
returns the day of the month (0-31). |
DAYOFWEEK(date) |
returns the day of the week of the given date . |
DAYOFYEAR(date) |
returns the day of the year of the given date . |
DEGREES(expr) |
returns the number of degrees in the radian expression given. |
EXPLODE(...) |
generates a new row in the result set for each element in the expressions provided. |
FIRST(expr) |
returns the first value in a sequence of elements of an aggregation. |
FLOOR(number) |
returns the largest integer value that is less than or equal to number . |
FROM_BASE64(str) |
decodes the base64-encoded string str . |
GREATEST(...) |
returns the greatest numeric or string value. |
HOUR(date) |
returns the hours of the given date . |
IFNULL(expr1, expr2) |
if expr1 is not NULL, it returns expr1 ; otherwise it returns expr2 . |
IF(expr1, expr2, expr3) |
if expr1 evaluates to true, retuns expr2 . Otherwise returns expr3 . |
INSTR(str1, str2) |
returns the 1-based index of the first occurence of str2 in str1 , or 0 if it does not occur. |
IS_BINARY(blob) |
returns whether a blob is a binary file or not. |
JSON_EXTRACT(json_doc, path, ...) |
extracts data from a json document using json paths. Extracting a string will result in that string being quoted. To avoid this, use JSON_UNQUOTE(JSON_EXTRACT(json_doc, path, ...)) . |
JSON_UNQUOTE(json) |
unquotes JSON value and returns the result as a utf8mb4 string. |
LAST(expr) |
returns the last value in a sequence of elements of an aggregation. |
LEAST(...) |
returns the smaller numeric or string value. |
LEFT(str, int) |
returns the first N characters in the string given. |
LENGTH(str) |
returns the length of the string in bytes. |
LN(X) |
returns the natural logarithm of X . |
LOG(X), LOG(B, X) |
if called with one parameter, this function returns the natural logarithm of X . If called with two parameters, this function returns the logarithm of X to the base B . If X is less than or equal to 0, or if B is less than or equal to 1, then NULL is returned. |
LOG10(X) |
returns the base-10 logarithm of X . |
LOG2(X) |
returns the base-2 logarithm of X . |
LOWER(str) |
returns the string str with all characters in lower case. |
LPAD(str, len, padstr) |
returns the string str , left-padded with the string padstr to a length of len characters. |
LTRIM(str) |
returns the string str with leading space characters removed. |
MAX(expr) |
returns the maximum value of expr in all rows. |
MID(str, pos, [len]) |
returns a substring from the provided string starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken. |
MIN(expr) |
returns the minimum value of expr in all rows. |
MINUTE(date) |
returns the minutes of the given date . |
MONTH(date) |
returns the month of the given date . |
NOW() |
returns the current timestamp. |
NULLIF(expr1, expr2) |
returns NULL if expr1 = expr2 is true, otherwise returns expr1 . |
POW(X, Y) |
returns the value of X raised to the power of Y . |
POWER(X, Y) |
synonym for POW |
RADIANS(expr) |
returns the radian value of the degrees argument given |
RAND(expr?) |
returns a random number in the range 0 <= x < 1. If an argument is given, it is used to seed the random number generator. |
REGEXP_MATCHES(text, pattern, [flags]) |
returns an array with the matches of the pattern in the given text . Flags can be given to control certain behaviours of the regular expression. Currently, only the i flag is supported, to make the comparison case insensitive. |
REPEAT(str, count) |
returns a string consisting of the string str repeated count times. |
REPLACE(str,from_str,to_str) |
returns the string str with all occurrences of the string from_str replaced by the string to_str . |
REVERSE(str) |
returns the string str with the order of the characters reversed. |
ROUND(number, decimals) |
rounds the number to decimals decimal places. |
RPAD(str, len, padstr) |
returns the string str , right-padded with the string padstr to a length of len characters. |
RTRIM(str) |
returns the string str with trailing space characters removed. |
SECOND(date) |
returns the seconds of the given date . |
SIN(expr) |
returns the sine of the expression given. |
SLEEP(seconds) |
waits for the specified number of seconds (can be fractional). |
SOUNDEX(str) |
returns the soundex of a string. |
SPLIT(str,sep) |
returns the parts of the string str split by the separator sep as a JSON array of strings. |
SQRT(X) |
returns the square root of a nonnegative number X . |
SUBSTR(str, pos, [len]) |
returns a substring from the string str starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken. |
SUBSTRING(str, pos, [len]) |
returns a substring from the string str starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken. |
SUBSTRING_INDEX(str, delim, count) |
Returns a substring after count appearances of delim . If count is negative, counts from the right side of the string. |
SUM(expr) |
returns the sum of expr in all rows. |
TAN(expr) |
returns the tangent of the expression given. |
TIMEDIFF(expr1, expr2) |
returns expr1 − expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type. |
TIMESTAMP(expr) |
returns a timestamp value for the expression given (e.g. the string '2020-01-02'). |
TO_BASE64(str) |
encodes the string str in base64 format. |
TRIM(str) |
returns the string str with all spaces removed. |
UNIX_TIMESTAMP(expr?) |
returns the datetime argument to the number of seconds since the Unix epoch. With nor argument, returns the number of execonds since the Unix epoch for the current time. |
UPPER(str) |
returns the string str with all characters in upper case. |
USER() |
returns the current user name. |
UTC_TIMESTAMP() |
returns the current UTC timestamp. |
WEEKDAY(date) |
returns the weekday of the given date . |
YEAR(date) |
returns the year of the given date . |
YEARWEEK(date, mode) |
returns year and week for a date. The year in the result may be different from the year in the date argument for the first and the last week of the year. |
The behaviour of certain parts of go-mysql-server can be configured using either environment variables or session variables.
Session variables are set using the following SQL queries:
SET <variable name> = <value>
Name | Type | Description |
---|---|---|
INMEMORY_JOINS |
environment | If set it will perform all joins in memory. Default is off. |
inmemory_joins |
session | If set it will perform all joins in memory. Default is off. This has precedence over INMEMORY_JOINS . |
MAX_MEMORY |
environment | The maximum number of memory, in megabytes, that can be consumed by go-mysql-server. Any in-memory caches or computations will no longer try to use memory when the limit is reached. Note that this may cause certain queries to fail if there is not enough memory available, such as queries using DISTINCT, ORDER BY or GROUP BY with groupings. |
DEBUG_ANALYZER |
environment | If set, the analyzer will print debug messages. Default is off. |
go-mysql-server
contains a SQL engine and server implementation. So,
if you want to start a server, first instantiate the engine and pass
your sql.Database
implementation.
It will be in charge of handling all the logic to retrieve the data from your source. Here you can see an example using the in-memory database implementation:
import (
"time"
"github.com/dolthub/go-mysql-server/auth"
"github.com/dolthub/go-mysql-server/memory"
"github.com/dolthub/go-mysql-server/server"
"github.com/dolthub/go-mysql-server/sql"
sqle "github.com/dolthub/go-mysql-server"
)
func main() {
driver := sqle.NewDefault()
driver.AddDatabase(createTestDatabase())
config := server.Config{
Protocol: "tcp",
Address: "localhost:3306",
Auth: auth.NewNativeSingle("user", "pass", auth.AllPermissions),
}
s, err := server.NewDefaultServer(config, driver)
if err != nil {
panic(err)
}
s.Start()
}
func createTestDatabase() *memory.Database {
const (
dbName = "test"
tableName = "mytable"
)
db := memory.NewDatabase(dbName)
table := memory.NewTable(tableName, sql.Schema{
{Name: "name", Type: sql.Text, Nullable: false, Source: tableName},
{Name: "email", Type: sql.Text, Nullable: false, Source: tableName},
{Name: "phone_numbers", Type: sql.JSON, Nullable: false, Source: tableName},
{Name: "created_at", Type: sql.Timestamp, Nullable: false, Source: tableName},
})
db.AddTable(tableName, table)
ctx := sql.NewEmptyContext()
rows := []sql.Row{
sql.NewRow("John Doe", "[email protected]", []string{"555-555-555"}, time.Now()),
sql.NewRow("John Doe", "[email protected]", []string{}, time.Now()),
sql.NewRow("Jane Doe", "[email protected]", []string{}, time.Now()),
sql.NewRow("Evil Bob", "[email protected]", []string{"555-666-555", "666-666-666"}, time.Now()),
}
for _, row := range rows {
table.Insert(ctx, row)
}
return db
}
Then, you can connect to the server with any MySQL client:
> mysql --host=127.0.0.1 --port=3306 -u user -ppass test -e "SELECT * FROM mytable"
+----------+-------------------+-------------------------------+---------------------+
| name | email | phone_numbers | created_at |
+----------+-------------------+-------------------------------+---------------------+
| John Doe | [email protected] | ["555-555-555"] | 2018-04-18 10:42:58 |
| John Doe | [email protected] | [] | 2018-04-18 10:42:58 |
| Jane Doe | [email protected] | [] | 2018-04-18 10:42:58 |
| Evil Bob | [email protected] | ["555-666-555","666-666-666"] | 2018-04-18 10:42:58 |
+----------+-------------------+-------------------------------+---------------------+
See the complete example here.
SELECT count(name) FROM mytable
+---------------------+
| COUNT(mytable.name) |
+---------------------+
| 4 |
+---------------------+
SELECT name,year(created_at) FROM mytable
+----------+--------------------------+
| name | YEAR(mytable.created_at) |
+----------+--------------------------+
| John Doe | 2018 |
| John Doe | 2018 |
| Jane Doe | 2018 |
| Evil Bob | 2018 |
+----------+--------------------------+
SELECT email FROM mytable WHERE name = 'Evil Bob'
+-------------------+
| email |
+-------------------+
| [email protected] |
+-------------------+
To create your own data source implementation you need to implement the following interfaces:
-
sql.Database
interface. This interface will provide tables from your data source. You can also implement other interfaces on your database to unlock additional functionality:sql.TableCreator
to support creating new tablessql.TableDropper
to support dropping tablessql.TableRenamer
to support renaming tablessql.ViewCreator
to support creating persisted views on your tablessql.ViewDropper
to support dropping persisted views
-
sql.Table
interface. This interface will provide rows of values from your data source. You can also implement other interfaces on your table to unlock additional functionality:sql.InsertableTable
to allow your data source to be updated withINSERT
statements.sql.UpdateableTable
to allow your data source to be updated withUPDATE
statements.sql.DeletableTable
to allow your data source to be updated withDELETE
statements.sql.ReplaceableTable
to allow your data source to be updated withREPLACE
statements.sql.AlterableTable
to allow your data source to have its schema modified by adding, dropping, and altering columns.sql.IndexedTable
to declare your table's native indexes to speed up query execution.sql.IndexAlterableTable
to accept the creation of new native indexes.sql.ForeignKeyAlterableTable
to signal your support of foreign key constraints in your table's schema and data.sql.ProjectedTable
to return rows that only contain a subset of the columns in the table. This can make query execution faster.sql.FilteredTable
to filter the rows returned by your table to those matching a given expression. This can make query execution faster (if your table implementation can filter rows more efficiently than checking an expression on every row in a table).
You can see a really simple data source implementation in the memory
package.
go-mysql-server provides a suite of engine tests that you can use
to validate that your implementation works as expected. See the
enginetest
package for details and examples.
go-mysql-server
exposes a series of interfaces to allow you to
implement your own indexes so you can speed up your queries.
Tables can declare that they support native indexes, which means that
they support efficiently returning a subset of their rows that match
an expression. The memory
package contains an example of this
behavior, but please note that it is only for example purposes and
doesn't actually make queries faster (although we could change this in
the future).
Integrators should implement the sql.IndexedTable
interface to
declare which indexes their tables support and provide a means of
returning a subset of the rows based on an sql.IndexLookup
provided
by their sql.Index
implementation. There are a variety of extensions
to sql.Index
that can be implemented, each of which unlocks
additional capabilities:
sql.Index
. Base-level interface, supporting equality lookups for an index.sql.AscendIndex
. Adds support for>
and>=
indexed lookups.sql.DescendIndex
. Adds support for<
and<=
indexed lookups.sql.NegateIndex
. Adds support for negating other index lookups.sql.MergeableIndexLookup
. Adds support for merging twosql.IndexLookup
s together to create a new one, representingAND
andOR
expressions on indexed columns.
Index drivers provide different backends for storing and querying indexes, without the need for a table to store and query its own native indexes. To implement a custom index driver you need to implement a few things:
sql.IndexDriver
interface, which will be the driver itself. Not that your driver must return an unique ID in theID
method. This ID is unique for your driver and should not clash with any other registered driver. It's the driver's responsibility to be fault tolerant and be able to automatically detect and recover from corruption in indexes.sql.Index
interface, returned by your driver when an index is loaded or created.sql.IndexValueIter
interface, which will be returned by yoursql.IndexLookup
and should return the values of the index.- Don't forget to register the index driver in your
sql.Context
usingcontext.RegisterIndexDriver(mydriver)
to be able to use it.
To create indexes using your custom index driver you need to use
extension syntax USING driverid
on the index creation statement. For
example:
CREATE INDEX foo ON table USING driverid (col1, col2)
go-mysql-server does not provide a production index driver implementation. We previously provided a pilosa implementation, but removed it due to the difficulty of supporting it on all platforms (pilosa doesn't work on Windows).
You can see an example of a driver implementation in the memory package.
go-mysql-server
utilizes github.com/go-kit/kit/metrics
module to
expose metrics (counters, gauges, histograms) for certain packages (so
far for engine
, analyzer
, regex
). If you already have
metrics server (prometheus, statsd/statsite, influxdb, etc.) and you
want to gather metrics also from go-mysql-server
components, you
will need to initialize some global variables by particular
implementations to satisfy following interfaces:
// Counter describes a metric that accumulates values monotonically.
type Counter interface {
With(labelValues ...string) Counter
Add(delta float64)
}
// Gauge describes a metric that takes specific values over time.
type Gauge interface {
With(labelValues ...string) Gauge
Set(value float64)
Add(delta float64)
}
// Histogram describes a metric that takes repeated observations of the same
// kind of thing, and produces a statistical summary of those observations,
// typically expressed as quantiles or buckets.
type Histogram interface {
With(labelValues ...string) Histogram
Observe(value float64)
}
You can use one of go-kit
implementations or try your own. For
instance, we want to expose metrics for prometheus server. So,
before we start mysql engine, we have to set up the following
variables:
import(
"github.com/go-kit/kit/metrics/prometheus"
promopts "github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
//....
// engine metrics
sqle.QueryCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
Namespace: "go_mysql_server",
Subsystem: "engine",
Name: "query_counter",
}, []string{
"query",
})
sqle.QueryErrorCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
Namespace: "go_mysql_server",
Subsystem: "engine",
Name: "query_error_counter",
}, []string{
"query",
"error",
})
sqle.QueryHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
Namespace: "go_mysql_server",
Subsystem: "engine",
Name: "query_histogram",
}, []string{
"query",
"duration",
})
// analyzer metrics
analyzer.ParallelQueryCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
Namespace: "go_mysql_server",
Subsystem: "analyzer",
Name: "parallel_query_counter",
}, []string{
"parallelism",
})
// regex metrics
regex.CompileHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
Namespace: "go_mysql_server",
Subsystem: "regex",
Name: "compile_histogram",
}, []string{
"regex",
"duration",
})
regex.MatchHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
Namespace: "go_mysql_server",
Subsystem: "regex",
Name: "match_histogram",
}, []string{
"string",
"duration",
})
One important note - internally we set some labels for metrics,
that's why have to pass those keys like "duration", "query", "driver",
... when we register metrics in prometheus
. Other systems may have
different requirements.
go-mysql-server was originally developed by the {source-d} organzation, and this repository was originally forked from src-d. We want to thank the entire {source-d} development team for their work on this project, especially Miguel Molina (@erizocosmico) and Juanjo Álvarez Martinez (@juanjux).
Apache License 2.0, see LICENSE