collations: Refactor to separate basic collation information from data

This refactor separates the full collation data and tables from the basic collation information like names etc. With this separation, tools like `mysqlctld` and `vtbackup` can run without having to compile collation data into the binary at all, since they only depend on basic name functionality for the MySQL protocol bits but they don't need the full collations data package. Reduces the binary size significantly and removes it from in-memory in the process. Before ``` -rwxr-xr-x 1 dirkjan staff 41336562 Aug 10 14:25 mysqlctl* -rwxr-xr-x 1 dirkjan staff 42197394 Aug 10 14:25 mysqlctld* -rwxr-xr-x 1 dirkjan staff 67138226 Aug 10 14:25 vtbackup* ``` After ``` -rwxr-xr-x 1 dirkjan staff 35649490 Aug 10 14:25 mysqlctl* -rwxr-xr-x 1 dirkjan staff 36509970 Aug 10 14:25 mysqlctld* -rwxr-xr-x 1 dirkjan staff 61432706 Aug 10 14:25 vtbackup* ``` This step enforces the separation between these packages which means that lazy loading of actually used collation information also becomes possible and much simpler with this refactor. Signed-off-by: Dirkjan Bussink <[email protected]>
vitessio · Aug 29, 2023 · 66dd93a · 66dd93a
1 parent 68285b3
commit 66dd93a
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Showing 86 changed files with 1,818 additions and 1,324 deletions.
diff --git a/go.mod b/go.mod
@@ -72,15 +72,15 @@ require (
 	go.etcd.io/etcd/client/pkg/v3 v3.5.8
 	go.etcd.io/etcd/client/v3 v3.5.8
 	go.uber.org/mock v0.2.0
-	golang.org/x/crypto v0.8.0 // indirect
-	golang.org/x/mod v0.11.0 // indirect
-	golang.org/x/net v0.9.0
+	golang.org/x/crypto v0.12.0 // indirect
+	golang.org/x/mod v0.12.0 // indirect
+	golang.org/x/net v0.14.0
 	golang.org/x/oauth2 v0.7.0
-	golang.org/x/sys v0.8.0 // indirect
-	golang.org/x/term v0.8.0
-	golang.org/x/text v0.9.0
+	golang.org/x/sys v0.11.0 // indirect
+	golang.org/x/term v0.11.0
+	golang.org/x/text v0.12.0
 	golang.org/x/time v0.3.0
-	golang.org/x/tools v0.8.0
+	golang.org/x/tools v0.12.1-0.20230815132531-74c255bcf846
 	google.golang.org/api v0.121.0
 	google.golang.org/genproto v0.0.0-20230410155749-daa745c078e1 // indirect
 	google.golang.org/grpc v1.55.0-dev
@@ -107,7 +107,7 @@ require (
 	github.com/spf13/jwalterweatherman v1.1.0
 	github.com/xlab/treeprint v1.2.0
 	go.uber.org/goleak v1.2.1
-	golang.org/x/sync v0.1.0
+	golang.org/x/sync v0.3.0
 	modernc.org/sqlite v1.20.3
 )
 

diff --git a/go.sum b/go.sum
@@ -667,8 +667,8 @@ golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5y
 golang.org/x/crypto v0.0.0-20211108221036-ceb1ce70b4fa/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.0.0-20211117183948-ae814b36b871/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/crypto v0.0.0-20220314234659-1baeb1ce4c0b/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
-golang.org/x/crypto v0.8.0 h1:pd9TJtTueMTVQXzk8E2XESSMQDj/U7OUu0PqJqPXQjQ=
-golang.org/x/crypto v0.8.0/go.mod h1:mRqEX+O9/h5TFCrQhkgjo2yKi0yYA+9ecGkdQoHrywE=
+golang.org/x/crypto v0.12.0 h1:tFM/ta59kqch6LlvYnPa0yx5a83cL2nHflFhYKvv9Yk=
+golang.org/x/crypto v0.12.0/go.mod h1:NF0Gs7EO5K4qLn+Ylc+fih8BSTeIjAP05siRnAh98yw=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
@@ -705,8 +705,8 @@ golang.org/x/mod v0.4.1/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/mod v0.11.0 h1:bUO06HqtnRcc/7l71XBe4WcqTZ+3AH1J59zWDDwLKgU=
-golang.org/x/mod v0.11.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
+golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20180218175443-cbe0f9307d01/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -759,8 +759,8 @@ golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd/go.mod h1:CfG3xpIq0wQ8r1q4Su
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/net v0.1.0/go.mod h1:Cx3nUiGt4eDBEyega/BKRp+/AlGL8hYe7U9odMt2Cco=
 golang.org/x/net v0.3.0/go.mod h1:MBQ8lrhLObU/6UmLb4fmbmk5OcyYmqtbGd/9yIeKjEE=
-golang.org/x/net v0.9.0 h1:aWJ/m6xSmxWBx+V0XRHTlrYrPG56jKsLdTFmsSsCzOM=
-golang.org/x/net v0.9.0/go.mod h1:d48xBJpPfHeWQsugry2m+kC02ZBRGRgulfHnEXEuWns=
+golang.org/x/net v0.14.0 h1:BONx9s002vGdD9umnlX1Po8vOZmrgH34qlHcD1MfK14=
+golang.org/x/net v0.14.0/go.mod h1:PpSgVXXLK0OxS0F31C1/tv6XNguvCrnXIDrFMspZIUI=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
@@ -784,8 +784,9 @@ golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.3.0 h1:ftCYgMx6zT/asHUrPw8BLLscYtGznsLAnjq5RH9P66E=
+golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -856,14 +857,14 @@ golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.3.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
-golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.1.0/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.3.0/go.mod h1:q750SLmJuPmVoN1blW3UFBPREJfb1KmY3vwxfr+nFDA=
-golang.org/x/term v0.8.0 h1:n5xxQn2i3PC0yLAbjTpNT85q/Kgzcr2gIoX9OrJUols=
-golang.org/x/term v0.8.0/go.mod h1:xPskH00ivmX89bAKVGSKKtLOWNx2+17Eiy94tnKShWo=
+golang.org/x/term v0.11.0 h1:F9tnn/DA/Im8nCwm+fX+1/eBwi4qFjRT++MhtVC4ZX0=
+golang.org/x/term v0.11.0/go.mod h1:zC9APTIj3jG3FdV/Ons+XE1riIZXG4aZ4GTHiPZJPIU=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -875,8 +876,8 @@ golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
 golang.org/x/text v0.4.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
-golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+golang.org/x/text v0.12.0 h1:k+n5B8goJNdU7hSvEtMUz3d1Q6D/XW4COJSJR6fN0mc=
+golang.org/x/text v0.12.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20191024005414-555d28b269f0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
@@ -936,8 +937,8 @@ golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
 golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/tools v0.4.0/go.mod h1:UE5sM2OK9E/d67R0ANs2xJizIymRP5gJU295PvKXxjQ=
-golang.org/x/tools v0.8.0 h1:vSDcovVPld282ceKgDimkRSC8kpaH1dgyc9UMzlt84Y=
-golang.org/x/tools v0.8.0/go.mod h1:JxBZ99ISMI5ViVkT1tr6tdNmXeTrcpVSD3vZ1RsRdN4=
+golang.org/x/tools v0.12.1-0.20230815132531-74c255bcf846 h1:Vve/L0v7CXXuxUmaMGIEK/dEeq7uiqb5qBgQrZzIE7E=
+golang.org/x/tools v0.12.1-0.20230815132531-74c255bcf846/go.mod h1:Sc0INKfu04TlqNoRA1hgpFZbhYXHPr4V5DzpSBTPqQM=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

diff --git a/go/mysql/collations/coercion.go b/go/mysql/collations/coercion.go
@@ -19,8 +19,6 @@ package collations
 import (
 	"fmt"
 	"unsafe"
-
-	"vitess.io/vitess/go/mysql/collations/charset"
 )
 
 func init() {
@@ -95,11 +93,6 @@ const (
 	RepertoireUnicode
 )
 
-// Coercion is a function that will transform either the given argument
-// arguments of the function into a specific character set. The `dst` argument
-// will be used as the destination of the coerced argument, but it can be nil.
-type Coercion func(dst, in []byte) ([]byte, error)
-
 // TypedCollation is the Collation of a SQL expression, including its coercibility
 // and repertoire.
 type TypedCollation struct {
@@ -112,208 +105,13 @@ func (tc TypedCollation) Valid() bool {
 	return tc.Collation != Unknown
 }
 
-func checkCompatibleCollations(
-	left Collation, leftCoercibility Coercibility, leftRepertoire Repertoire,
-	right Collation, rightCoercibility Coercibility, rightRepertoire Repertoire,
-) bool {
-	leftCS := left.Charset()
-	rightCS := right.Charset()
-
-	switch leftCS.(type) {
-	case charset.Charset_utf8mb4:
-		if leftCoercibility <= rightCoercibility {
-			return true
-		}
-
-	case charset.Charset_utf32:
-		switch {
-		case leftCoercibility < rightCoercibility:
-			return true
-		case leftCoercibility == rightCoercibility:
-			if !charset.IsUnicode(rightCS) {
-				return true
-			}
-			if !left.IsBinary() {
-				return true
-			}
-		}
-
-	case charset.Charset_utf8mb3, charset.Charset_ucs2, charset.Charset_utf16, charset.Charset_utf16le:
-		switch {
-		case leftCoercibility < rightCoercibility:
-			return true
-		case leftCoercibility == rightCoercibility:
-			if !charset.IsUnicode(rightCS) {
-				return true
-			}
-		}
-	}
-
-	if rightRepertoire == RepertoireASCII {
-		switch {
-		case leftCoercibility < rightCoercibility:
-			return true
-		case leftCoercibility == rightCoercibility:
-			if leftRepertoire == RepertoireUnicode {
-				return true
-			}
-		}
-	}
-
-	return false
-}
-
-// CoercionOptions is used to configure how aggressive the algorithm can be
-// when merging two different collations by transcoding them.
-type CoercionOptions struct {
-	// ConvertToSuperset allows merging two different collations as long
-	// as the charset of one of them is a strict superset of the other. In
-	// order to operate on the two expressions, one of them will need to
-	// be transcoded. This transcoding will always be safe because the string
-	// with the smallest repertoire will be transcoded to its superset, which
-	// cannot fail.
-	ConvertToSuperset bool
-
-	// ConvertWithCoercion allows merging two different collations by forcing
-	// a coercion as long as the coercibility of the two sides is lax enough.
-	// This will force a transcoding of one of the expressions even if their
-	// respective charsets are not a strict superset, so the resulting transcoding
-	// CAN fail depending on the content of their strings.
-	ConvertWithCoercion bool
-}
-
-// MergeCollations returns a Coercion function for a pair of TypedCollation based
-// on their coercibility.
-//
-// The function takes the typed collations for the two sides of a text operation
-// (namely, a comparison or concatenation of two textual expressions). These typed
-// collations includes the actual collation for the expression on each size, their
-// coercibility values (see: Coercibility) and their respective repertoires,
-// and returns the target collation (i.e. the collation into which the two expressions
-// must be coerced, and a Coercion function. The Coercion function can be called repeatedly
-// with the different values for the two expressions and will transcode either
-// the left-hand or right-hand value to the appropriate charset so it can be
-// collated against the other value.
-//
-// If the collations for both sides of the expressions are the same, the returned
-// Coercion function will be a no-op. Likewise, if the two collations are not the same,
-// but they are compatible and have the same charset, the Coercion function will also
-// be a no-op.
-//
-// If the collations for both sides of the expression are not compatible, an error
-// will be returned and the returned TypedCollation and Coercion will be nil.
-func (env *Environment) MergeCollations(left, right TypedCollation, opt CoercionOptions) (TypedCollation, Coercion, Coercion, error) {
-	leftColl := left.Collation.Get()
-	rightColl := right.Collation.Get()
-	if leftColl == nil || rightColl == nil {
-		return TypedCollation{}, nil, nil, fmt.Errorf("unsupported TypeCollationID: %v / %v", left.Collation, right.Collation)
-	}
-
-	leftCS := leftColl.Charset()
-	rightCS := rightColl.Charset()
-
-	if left.Coercibility == CoerceExplicit && right.Coercibility == CoerceExplicit {
-		if left.Collation != right.Collation {
-			goto cannotCoerce
-		}
-	}
-
-	if leftCS.Name() == rightCS.Name() {
-		switch {
-		case left.Coercibility < right.Coercibility:
-			left.Repertoire |= right.Repertoire
-			return left, nil, nil, nil
-
-		case left.Coercibility > right.Coercibility:
-			right.Repertoire |= left.Repertoire
-			return right, nil, nil, nil
-
-		case left.Collation == right.Collation:
-			left.Repertoire |= right.Repertoire
-			return left, nil, nil, nil
-		}
-
-		if left.Coercibility == CoerceExplicit {
-			goto cannotCoerce
-		}
-
-		leftCsBin := leftColl.IsBinary()
-		rightCsBin := rightColl.IsBinary()
-
-		switch {
-		case leftCsBin && rightCsBin:
-			left.Coercibility = CoerceNone
-			return left, nil, nil, nil
-
-		case leftCsBin:
-			return left, nil, nil, nil
-
-		case rightCsBin:
-			return right, nil, nil, nil
-		}
-
-		defaults := env.byCharset[leftCS.Name()]
-		return TypedCollation{
-			Collation:    defaults.Binary.ID(),
-			Coercibility: CoerceNone,
-			Repertoire:   left.Repertoire | right.Repertoire,
-		}, nil, nil, nil
-	}
-
-	if _, leftIsBinary := leftColl.(*Collation_binary); leftIsBinary {
-		if left.Coercibility <= right.Coercibility {
-			return left, nil, nil, nil
-		}
-		goto coerceToRight
-	}
-	if _, rightIsBinary := rightColl.(*Collation_binary); rightIsBinary {
-		if left.Coercibility >= right.Coercibility {
-			return right, nil, nil, nil
-		}
-		goto coerceToLeft
-	}
-
-	if opt.ConvertToSuperset {
-		if checkCompatibleCollations(leftColl, left.Coercibility, left.Repertoire, rightColl, right.Coercibility, right.Repertoire) {
-			goto coerceToLeft
-		}
-		if checkCompatibleCollations(rightColl, right.Coercibility, right.Repertoire, leftColl, left.Coercibility, left.Repertoire) {
-			goto coerceToRight
-		}
-	}
-
-	if opt.ConvertWithCoercion {
-		if left.Coercibility < right.Coercibility && right.Coercibility > CoerceImplicit {
-			goto coerceToLeft
-		}
-		if right.Coercibility < left.Coercibility && left.Coercibility > CoerceImplicit {
-			goto coerceToRight
-		}
-	}
-
-cannotCoerce:
-	return TypedCollation{}, nil, nil, fmt.Errorf("Illegal mix of collations (%s,%s) and (%s,%s)",
-		leftColl.Name(), left.Coercibility, rightColl.Name(), right.Coercibility)
-
-coerceToLeft:
-	return left, nil,
-		func(dst, in []byte) ([]byte, error) {
-			return charset.Convert(dst, leftCS, in, rightCS)
-		}, nil
-
-coerceToRight:
-	return right,
-		func(dst, in []byte) ([]byte, error) {
-			return charset.Convert(dst, rightCS, in, leftCS)
-		}, nil, nil
-}
-
 func (env *Environment) EnsureCollate(fromID, toID ID) error {
 	// these two lookups should never fail
-	from := fromID.Get()
-	to := toID.Get()
-	if from.Charset().Name() != to.Charset().Name() {
-		return fmt.Errorf("COLLATION '%s' is not valid for CHARACTER SET '%s'", to.Name(), from.Charset().Name())
+	fromCharsetName := env.LookupCharsetName(fromID)
+	toCharsetName := env.LookupCharsetName(toID)
+	if fromCharsetName != toCharsetName {
+		toCollName := env.LookupName(toID)
+		return fmt.Errorf("COLLATION '%s' is not valid for CHARACTER SET '%s'", toCollName, fromCharsetName)
 	}
 	return nil
 }