In WP_Meta_Query, don't cast meta_value to CHAR.

`CHAR` is redundant, since the `meta_value` column is `LONGTEXT`. Meanwhile,
use of `CAST()` causes MySQL to ignore any index that the administrator may
have added to the column.

A number of automated tests were doing searches for `CAST` in the SQL strings
generated by `WP_Meta_Query` (for reasons unrelated to the `CAST()` behavior).
These tests have been updated to expect the new query format.

Props ericlewis.
Fixes #36625.

git-svn-id: https://develop.svn.wordpress.org/trunk@37594 602fd350-edb4-49c9-b593-d223f7449a82

Author: boonebgorges

src/wp-includes/class-wp-meta-query.php

@@ -632,7 +632,11 @@ public function get_sql_for_clause( &$clause, $parent_query, $clause_key = '' )
 			}
 
 			if ( $where ) {
-				$sql_chunks['where'][] = "CAST($alias.meta_value AS {$meta_type}) {$meta_compare} {$where}";
+				if ( 'CHAR' === $meta_type ) {
+					$sql_chunks['where'][] = "$alias.meta_value {$meta_compare} {$where}";
+				} else {
+					$sql_chunks['where'][] = "CAST($alias.meta_value AS {$meta_type}) {$meta_compare} {$where}";
+				}
 			}
 		}
 

tests/phpunit/tests/meta/query.php

@@ -493,7 +493,7 @@ public function test_null_value_sql() {
 		) );
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertEquals( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) = ''" ) );
+		$this->assertEquals( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value = ''" ) );
 	}
 
 	/**
@@ -601,7 +601,7 @@ public function test_convert_null_value_to_empty_string() {
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertSame( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) = ''" ) );
+		$this->assertSame( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value = ''" ) );
 	}
 
 	public function test_get_sql_convert_lowercase_compare_to_uppercase() {
@@ -632,7 +632,7 @@ public function test_get_sql_empty_meta_compare_with_array_value() {
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertSame( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) IN" ) );
+		$this->assertSame( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value IN" ) );
 	}
 
 	public function test_get_sql_empty_meta_compare_with_non_array_value() {
@@ -647,7 +647,7 @@ public function test_get_sql_empty_meta_compare_with_non_array_value() {
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertSame( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) =" ) );
+		$this->assertSame( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value =" ) );
 	}
 
 	public function test_get_sql_invalid_meta_compare() {
@@ -663,7 +663,7 @@ public function test_get_sql_invalid_meta_compare() {
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertSame( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) =" ) );
+		$this->assertSame( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value =" ) );
 	}
 
 	/**
@@ -760,7 +760,7 @@ public function test_get_sql_trim_string_value() {
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 
-		$this->assertSame( 1, substr_count( $sql['where'], "CAST($wpdb->postmeta.meta_value AS CHAR) = 'bar'" ) );
+		$this->assertSame( 1, substr_count( $sql['where'], "$wpdb->postmeta.meta_value = 'bar'" ) );
 	}
 
 	public function test_not_exists() {