esql

README

ESQL: Translate SQL to Elasticsearch DSL

Use SQL to query Elasticsearch. ES V6 compatible.

Supported features

• =, !=, <, >, <=, >=, <>, ()
• comparison with arithmetics (e.g. colA + 1 < colB * 2)
• arithmetic operators: +, -, *, /, %, >>, <<, ()
• AND, OR, NOT
• LIKE, IN, REGEX, IS NULL, BETWEEN
• LIMIT, SIZE, DISTINCT
• COUNT, COUNT(DISTINCT)
• AVG, MAX, MIN, SUM
• GROUP BY, ORDER BY
• HAVING
• query key value macro (see usage)
• pagination (search after)
• pagination for aggregation
• functions
• JOIN
• nested queries

Usage

Please refer to code and comments in esql.go. esql.go contains all the apis that an outside user needs.

Basic Usage

sql := `SELECT COUNT(*), MAX(colA) FROM myTable WHERE colB < 10 GROUP BY colC HAVING COUNT(*) > 20`
e := NewESql()
dsl, _, err := e.ConvertPretty(sql)    // convert sql to dsl
if err == nil {
    fmt.Println(dsl)
}

Custom Query Macro

ESQL support API ProcessQueryKey to register custom policy for colName replacement. It accepts 2 functions, the first function determines whether a colName is to be replaced, the second specifies how to do the replacement. Use case: user has custom field field, but to resolve confict, server stores the field as Custom.field. ProcessQueryKey API can automatically do the conversion.

ESQL support API ProcessQueryValue to register custom policy for value processing. It accepts 2 functions, the first function determines whether a value of a colName is to be processed, the second specifies how to do the processing. Use case: user want to query time in readable format, but server stores time as an integer (unix nano). ProcessQueryValue API can automatically do the conversion.

Below shows an example.

sql := "SELECT colA FROM myTable WHERE colB < 10 AND dateTime = '2015-01-01T02:59:59Z'"
// custom policy that change colName like "col.." to "myCol.."
func myKeyFilter(colName string) bool {
    return strings.HasPrefix(colName, "col")
}
func myKeyProcess(colName string) (string, error) {
    return "myCol"+colName[3:], nil
}
// custom policy that convert formatted time string to unix nano
func myValueFilter(colName string) bool {
    return strings.Contains(colName, "Time") || strings.Contains(colName, "time")
}
func myValueProcess(timeStr string) (string, error) {
    // convert formatted time string to unix nano integer
    parsedTime, _ := time.Parse(defaultDateTimeFormat, timeStr)
    return fmt.Sprintf("%v", parsedTime.UnixNano()), nil
}
// with the 2 policies , converted dsl is equivalent to
// "SELECT myColA FROM myTable WHERE myColB < 10 AND dateTime = '1561678568048000000'
// in which the time is in unix nano format
e := NewESql()
e.ProcessQueryKey(myKeyFilter, myKeyProcess)            // set up macro for key
e.ProcessQueryValue(myValueFilter, myValueProcess)      // set up macro for value
dsl, _, err := e.ConvertPretty(sql)                     // convert sql to dsl
if err == nil {
    fmt.Println(dsl)
}

Pagination

ESQL support 2 kinds of pagination: FROM keyword and ES search_after.

• FROM keyword: the same as SQL syntax. Be careful, ES only support a page smaller than 10k, if your offset is large than 10k, search_after is necessary.
• search_after: Once you know the paging tokens, just feed them to Convert or ConvertPretty API in order.

Below shows an example.

// first page
sql_page1 := "SELECT * FROM myTable ORDER BY colA, colB LIMIT 10"
e := NewESql()
dsl_page1, sortFields, err := e.ConvertPretty(sql_page1)

// second page
// 1. Use FROM to retrieve the 2nd page
sql_page2_FROM := "SELECT * FROM myTable ORDER BY colA, colB LIMIT 10 FROM 10"
dsl_page2_FROM, sortFields, err := e.ConvertPretty(sql_page2_FROM)

// 2. Use search_after to retrieve the 2nd page
// we can use sortFields and the query result from page 1 to get the page tokens
sql_page2_search_after := sql_page1
page_token_colA := "123"
page_token_colB := "bbc"
dsl_page2_search_after, sortFields, err := e.ConvertPretty(sql_page2_search_after, page_colA, page_colB)

For Temporal usage, refer to this link.

ES V2.x vs ES V6.5

Item	ES V2.x	ES v6.5
missing check	{"missing": {"field": "xxx"}}	{"must_not": {"exist": {"field": "xxx"}}}
group by multiple columns	nested "aggs" field	"composite" flattened grouping

Attentions

• If you want to apply aggregation on some fields, they should not be in type text in ES
• COUNT(colName) will include documents w/ null values in that column in ES SQL API, while in esql we exclude null valued documents
• ES SQL API and esql do not support SELECT DISTINCT, a workaround is to query something like SELECT * FROM table GROUP BY colName
• ES SQL API does not support ORDER BY aggregation, esql support it by applying bucket_sort
• ES SQL API does not support HAVING aggregation that not show up in SELECT, esql support it
• To use regex query, the column should be keyword type, otherwise the regex is applied to all the terms produced by tokenizer from the original text rather than the original text itself
• Comparison with arithmetics can be potentially slow since it uses scripting query and thus is not able to take advantage of reverse index. For binary operators, please refer to this link on the precedence. We don't support all of them.
• Comparison with arithmetics does not support date type

Acknowledgement

This project is originated from elasticsql. Table below shows the improvement.

Item	detail
comparison	support comparison with arithmetics of different columns
keyword IS	support standard SQL keywords IS NULL, IS NOT NULL for missing check
keyword NOT	support NOT, convert NOT recursively since elasticsearch's must_not is not the same as boolean operator NOT in sql
keyword LIKE	using "wildcard" tag, support SQL wildcard '%' and '_'
keyword REGEX	using "regexp" tag, support standard regular expression syntax
keyword GROUP BY	using "composite" tag to flatten multiple grouping
keyword ORDER BY	using "bucket_sort" to support order by aggregation functions
keyword HAVING	using "bucket_selector" and painless scripting language to support HAVING
aggregations	allow introducing aggregation functions from all HAVING, SELECT, ORDER BY
column name filtering	allow user pass an white list, when the sql query tries to select column out side white list, refuse the converting
column name replacing	allow user pass an function as initializing parameter, the matched column name will be replaced upon the policy
query value replacing	allow user pass an function as initializing parameter, query value will be processed by such function if the column name matched in filter function
pagination	also return the sorting fields for future search after usage
optimization	using "filter" tag rather than "must" tag to avoid scoring analysis and save time
optimization	no redundant {"bool": {"filter": xxx}} wrapped
optimization	does not return document contents in aggregation query
optimization	only return fields user specifies after SELECT

Documentation

Index

• Constants
• type ESql
  • func NewESql() *ESql
  • func (e *ESql) Convert(sql string, pagination ...interface{}) (dsl string, sortField []string, err error)
  • func (e *ESql) ConvertPretty(sql string, pagination ...interface{}) (dsl string, sortField []string, err error)
  • func (e *ESql) ConvertPrettyTemporal(sql string, namespaceID string, pagination ...interface{}) (dsl string, sortFields []string, err error)
  • func (e *ESql) ConvertTemporal(sql string, namespaceID string, pagination ...interface{}) (dsl string, sortFields []string, err error)
  • func (e *ESql) ProcessQueryKey(filterArg FilterFunc, processArg ProcessFunc)
  • func (e *ESql) ProcessQueryValue(filterArg FilterFunc, processArg ProcessFunc)
  • func (e *ESql) SetBucketNum(bucketNumArg int)
  • func (e *ESql) SetPageSize(pageSizeArg int)
  • func (e *ESql) SetTemporal(temporalArg bool)
• type FilterFunc
• type ProcessFunc

Constants

const (
	DefaultPageSize      = 1000
	DefaultBucketNumber  = 1000
	ESDefaultMaxPageSize = 10000
	TieBreaker           = "RunId"
	RunID                = "RunId"
	StartTime            = "StartTime"
	NamespaceID          = "NamespaceId"
	WorkflowID           = "WorkflowId"
	ExecutionTime        = "ExecutionTime"
	TieBreakerOrder      = "desc"
	StartTimeOrder       = "desc"
)

default sizes and identifiers used in temporal visibility

Types

type ESql

type ESql struct {
	// contains filtered or unexported fields
}

ESql ... ESql is used to hold necessary information that required in parsing

func NewESql

func NewESql() *ESql

NewESql ... return a new default ESql

func (*ESql) Convert

func (e *ESql) Convert(sql string, pagination ...interface{}) (dsl string, sortField []string, err error)

Convert ... Transform sql to elasticsearch dsl string

usage:

• dsl, sortField, err := e.Convert(sql, pageParam1, pageParam2, ...)

arguments:

• sql: the sql query needs conversion in string format
• pagination: variadic arguments that indicates es search_after

return values:

• dsl: the elasticsearch dsl json style string
• sortField: string array that contains all column names used for sorting. useful for pagination.
• err: contains err information

func (*ESql) ConvertPretty

func (e *ESql) ConvertPretty(sql string, pagination ...interface{}) (dsl string, sortField []string, err error)

ConvertPretty ... Transform sql to elasticsearch dsl, and prettify the output json

usage:

• dsl, sortField, err := e.ConvertPretty(sql, pageParam1, pageParam2, ...)

arguments:

• sql: the sql query needs conversion in string format
• pagination: variadic arguments that indicates es search_after for pagination

return values:

• dsl: the elasticsearch dsl json style string
• sortField: string array that contains all column names used for sorting. useful for pagination.
• err: contains err information

func (*ESql) ConvertPrettyTemporal

func (e *ESql) ConvertPrettyTemporal(sql string, namespaceID string, pagination ...interface{}) (dsl string, sortFields []string, err error)

ConvertPrettyTemporal ... convert sql to es dsl, for temporal usage

func (*ESql) ConvertTemporal

func (e *ESql) ConvertTemporal(sql string, namespaceID string, pagination ...interface{}) (dsl string, sortFields []string, err error)

ConvertTemporal ... convert sql to es dsl, for temporal usage

func (*ESql) ProcessQueryKey

func (e *ESql) ProcessQueryKey(filterArg FilterFunc, processArg ProcessFunc)

ProcessQueryKey ... set up user specified column name processing policy should not be called if there is potential race condition

func (*ESql) ProcessQueryValue

func (e *ESql) ProcessQueryValue(filterArg FilterFunc, processArg ProcessFunc)

ProcessQueryValue ... set up user specified column value processing policy should not be called if there is potential race condition

func (*ESql) SetBucketNum

func (e *ESql) SetBucketNum(bucketNumArg int)

SetBucketNum ... set the number of bucket returned in an aggregation query should not be called if there is potential race condition

func (*ESql) SetPageSize

func (e *ESql) SetPageSize(pageSizeArg int)

SetPageSize ... set the number of documents returned in a non-aggregation query should not be called if there is potential race condition

func (*ESql) SetTemporal

func (e *ESql) SetTemporal(temporalArg bool)

SetTemporal ... specify whether do special handling for temporal visibility should not be called if there is potential race condition should not be called by non-temporal user

type FilterFunc

type FilterFunc func(string) bool

FilterFunc ... esql use FilterFunc to determine whether a target is to be processed by ProcessFunc only those FilterFunc(colName) == true will be processed

type ProcessFunc

type ProcessFunc func(string) (string, error)

ProcessFunc ... esql use ProcessFunc to process query key value macro