Add CHARINDEX function for sqlserver

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/Function.kt

@@ -137,6 +137,14 @@ class Trim<T : String?>(
     override fun toQueryBuilder(queryBuilder: QueryBuilder): Unit = queryBuilder { append("TRIM(", expr, ")") }
 }
 
+/**
+ * Represents an SQL function that returns the index of the first occurrence of [char] in [expr] or 0
+ */
+class CharIndex<T : String?>(val expr: Expression<T>, val char: String) : Function<Int>(IntegerColumnType()) {
+    override fun toQueryBuilder(queryBuilder: QueryBuilder) =
+        currentDialect.functionProvider.charIndex(queryBuilder, expr, char)
+}
+
 // General-Purpose Aggregate Functions
 
 /**

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/SQLExpressionBuilder.kt

@@ -40,6 +40,9 @@ fun <T : String?> Expression<T>.substring(start: Int, length: Int): Substring<T>
 /** Removes the longest string containing only spaces from both ends of string expression. */
 fun <T : String?> Expression<T>.trim(): Trim<T> = Trim(this)
 
+/** Returns the index of the first occurrence of [char] in this string expression or 0 if it doesn't contain [char] */
+fun <T : String?> Expression<T>.charIndex(char: String): CharIndex<T> = CharIndex(this, char)
+
 // General-Purpose Aggregate Functions
 
 /** Returns the minimum value of this expression across all non-null input values, or `null` if there are no non-null values. */

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/Default.kt

@@ -1,13 +1,12 @@
 package org.jetbrains.exposed.sql.vendors
 
+import org.jetbrains.exposed.exceptions.UnsupportedByDialectException
 import org.jetbrains.exposed.exceptions.throwUnsupportedException
 import org.jetbrains.exposed.sql.*
 import org.jetbrains.exposed.sql.transactions.TransactionManager
 import java.nio.ByteBuffer
 import java.util.*
 import java.util.concurrent.ConcurrentHashMap
-import kotlin.collections.HashMap
-import kotlin.collections.LinkedHashSet
 
 /**
  * Provides definitions for all the supported SQL data types.
@@ -208,6 +207,21 @@ abstract class FunctionProvider {
         append(")")
     }
 
+    /**
+     * SQL function that returns the index of the first occurrence of the given substring [char]
+     * in the string expression [expr]
+     *
+     * @param queryBuilder Query builder to append the SQL function to.
+     * @param expr String expression to find the substring in.
+     * @param char: Substring to find
+     * @return index of the first occurrence of [char] in [expr] starting from 1 or 0 if [expr] doesn't contain [char]
+     */
+    open fun <T : String?> charIndex(queryBuilder: QueryBuilder, expr: Expression<T>, char: String) {
+        throw UnsupportedByDialectException(
+            "There's no generic SQL for CHARINDEX. There must be vendor specific implementation.", currentDialect
+        )
+    }
+
     // Pattern matching
 
     /**

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLServerDialect.kt

@@ -73,6 +73,10 @@ internal object SQLServerFunctionProvider : FunctionProvider() {
         }
     }
 
+    override fun <T : String?> charIndex(queryBuilder: QueryBuilder, expr: Expression<T>, char: String) = queryBuilder {
+        append("CHARINDEX(\'", char, "\',", expr, ")")
+    }
+
     override fun <T : String?> regexp(
         expr1: Expression<T>,
         pattern: Expression<String>,

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/functions/FunctionsTests.kt

@@ -301,6 +301,42 @@ class FunctionsTests : DatabaseTestsBase() {
         }
     }
 
+    @Test
+    fun testCharIndex() {
+        withCitiesAndUsers(TestDB.values().asList().minus(TestDB.SQLSERVER)) { cities, _, _ ->
+            val charIndex = cities.name.charIndex("e")
+            val results = cities.slice(charIndex).selectAll().toList()
+
+            assertEquals(6, results[0][charIndex]) // St. Petersburg
+            assertEquals(0, results[1][charIndex]) // Munich
+            assertEquals(6, results[2][charIndex]) // Prague
+        }
+    }
+
+    @Test
+    fun testCharIndex02() {
+        withCitiesAndUsers(TestDB.values().asList().minus(TestDB.SQLSERVER)) { cities, _, _ ->
+            val charIndex = cities.name.charIndex("Peter")
+            val results = cities.slice(charIndex).selectAll().toList()
+
+            assertEquals(5, results[0][charIndex]) // St. Petersburg
+            assertEquals(0, results[1][charIndex]) // Munich
+            assertEquals(0, results[2][charIndex]) // Prague
+        }
+    }
+
+    @Test
+    fun testCharIndex03() {
+        withCitiesAndUsers(TestDB.values().asList().minus(TestDB.SQLSERVER)) { cities, _, _ ->
+            val charIndex = cities.name.charIndex("p")
+            val results = cities.slice(charIndex).selectAll().toList()
+
+            assertEquals(5, results[0][charIndex]) // St. Petersburg
+            assertEquals(0, results[1][charIndex]) // Munich
+            assertEquals(1, results[2][charIndex]) // Prague
+        }
+    }
+
     @Test
     fun testRandomFunction01() {
         val t = DMLTestsData.Cities