client/io.github.octaviusframework.client.query/QueryFragment

QueryFragment

class QueryFragment(val sql: String, val params: Map<String, Any?> = emptyMap())

A piece of SQL and the parameters it names, kept together so that neither can be dropped on the way.

The point of it is a WHERE assembled at runtime. Written as plain strings, a filter that is sometimes there and sometimes not means keeping a condition list and a parameter map in step by hand, and the failure when they drift is a parameter the query names and nobody supplied. Here the two travel together and join keeps them together.

val filter = listOfNotNull(
    name?.let { "cognomen ILIKE @name" withParam ("name" to "%$it%") },
    minRank?.let { "rank_order >= @minRank" withParam ("minRank" to it) },
    province?.let { "home_province = @province" withParam ("province" to it) }
).join(" AND ")

val senators = db.select("*").from("senate")
    .where(filter.sql)
    .fetchObjects<Senator>(filter.params)

The two halves are handed over separately and on purpose. A builder never carries parameters - that is what lets RunnableQuery.toSql be embedded in a larger statement without leaving values behind - so filter.sql goes to the clause and filter.params to the terminal. Writing both is what keeps the pair visible.

Constructors

QueryFragment

constructor(sql: String, params: Map<String, Any?> = emptyMap())

Properties

isEmpty

val isEmpty: Boolean

Whether this fragment contributes nothing, which is how a clause knows to leave itself out.

params

val params: Map<String, Any?>

The parameters the text names, by name and without the leading @.

sql

val sql: String

The SQL text of this fragment. Empty where the fragment contributes no condition.

Functions

toString

open override fun toString(): String