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feat(mysql): Add database analyzer for MySQL #4201

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e52cd4e
feat(mysql): Add database analyzer for MySQL
kyleconroy Nov 29, 2025
f1238e4
feat(mysql): Use forked driver to get prepared statement metadata
kyleconroy Nov 30, 2025
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feat(mysql): Use forked driver to get prepared statement metadata 
Updates the MySQL analyzer to use the sqlc-dev/mysql forked driver which
exposes column and parameter metadata from COM_STMT_PREPARE responses.
This provides more accurate type information directly from MySQL.

The forked driver adds a StmtMetadata interface with ColumnMetadata() and
ParamMetadata() methods that return type info including DatabaseTypeName,
Nullable, Unsigned, and Length fields.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>
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@kyleconroy @claude
kyleconroy and claude committed Nov 30, 2025
commit f1238e438f6a6fe14ce5eb568f85d5dd53b6b3fc
2 changes: 2 additions & 0 deletions go.mod
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Expand Up @@ -64,3 +64,5 @@ require (
google.golang.org/genproto/googleapis/rpc v0.0.0-20251022142026-3a174f9686a8 // indirect
gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
)

replace github.com/go-sql-driver/mysql => github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2
4 changes: 2 additions & 2 deletions go.sum
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Expand Up @@ -26,8 +26,6 @@ github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/go-sql-driver/mysql v1.9.3 h1:U/N249h2WzJ3Ukj8SowVFjdtZKfu9vlLZxjPXV1aweo=
github.com/go-sql-driver/mysql v1.9.3/go.mod h1:qn46aNg1333BRMNU69Lq93t8du/dwxI64Gl8i5p1WMU=
github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
github.com/gofrs/uuid v4.0.0+incompatible h1:1SD/1F5pU8p29ybwgQSwpQk+mwdRrXCYuPhW6m+TnJw=
github.com/gofrs/uuid v4.0.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
Expand Down Expand Up @@ -159,6 +157,8 @@ github.com/spf13/cobra v1.10.1/go.mod h1:7SmJGaTHFVBY0jW4NXGluQoLvhqFQM+6XSKD+P4
github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2 h1:kmCAKKtOgK6EXXQX9oPdEASIhgor7TCpWxD8NtcqVcU=
github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2/go.mod h1:TrDMWzjNTKvJeK2GC8uspG+PWyPLiY9QKvwdWpAdlZE=
github.com/stoewer/go-strcase v1.2.0 h1:Z2iHWqGXH00XYgqDmNgQbIBxf3wrNq0F3feEy0ainaU=
github.com/stoewer/go-strcase v1.2.0/go.mod h1:IBiWB2sKIp3wVVQ3Y035++gc+knqhUQag1KpM8ahLw8=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
Expand Down
192 changes: 82 additions & 110 deletions internal/engine/dolphin/analyzer/analyze.go
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Expand Up @@ -3,13 +3,14 @@ package analyzer
import (
"context"
"database/sql"
"database/sql/driver"
"fmt"
"hash/fnv"
"io"
"strings"
"sync"

_ "github.com/go-sql-driver/mysql"
"github.com/go-sql-driver/mysql"

core "github.com/sqlc-dev/sqlc/internal/analysis"
"github.com/sqlc-dev/sqlc/internal/config"
Expand Down Expand Up @@ -139,90 +140,102 @@ func (a *Analyzer) Analyze(ctx context.Context, n ast.Node, query string, migrat
}
}

// Count parameters in the query
paramCount := countParameters(query)

// Try to prepare the statement first to validate syntax
stmt, err := a.conn.PrepareContext(ctx, query)
// Get metadata directly from prepared statement via driver connection
result, err := a.getStatementMetadata(ctx, n, query, ps)
if err != nil {
return nil, a.extractSqlErr(n, err)
return nil, err
}
stmt.Close()

return result, nil
}

// getStatementMetadata uses the MySQL driver's prepared statement metadata API
// to get column and parameter type information without executing the query
func (a *Analyzer) getStatementMetadata(ctx context.Context, n ast.Node, query string, ps *named.ParamSet) (*core.Analysis, error) {
var result core.Analysis

// For SELECT queries, execute with default parameter values to get column metadata
if isSelectQuery(query) {
cols, err := a.getColumnMetadata(ctx, query, paramCount)
if err == nil {
result.Columns = cols
}
// If we fail to get column metadata, fall through to return empty columns
// and let the catalog-based inference handle it
// Get a raw connection to access driver-level prepared statement
conn, err := a.conn.Conn(ctx)
if err != nil {
return nil, a.extractSqlErr(n, fmt.Errorf("failed to get connection: %w", err))
}
defer conn.Close()

// Build parameter info
for i := 1; i <= paramCount; i++ {
name := ""
if ps != nil {
name, _ = ps.NameFor(i)
err = conn.Raw(func(driverConn any) error {
// Get the driver connection that supports PrepareContext
preparer, ok := driverConn.(driver.ConnPrepareContext)
if !ok {
return fmt.Errorf("driver connection does not support PrepareContext")
}
result.Params = append(result.Params, &core.Parameter{
Number: int32(i),
Column: &core.Column{
Name: name,
DataType: "any",
NotNull: false,
},
})
}

return &result, nil
}

// isSelectQuery checks if a query is a SELECT statement
func isSelectQuery(query string) bool {
trimmed := strings.TrimSpace(strings.ToUpper(query))
return strings.HasPrefix(trimmed, "SELECT") ||
strings.HasPrefix(trimmed, "WITH") // CTEs
}
// Prepare the statement - this sends COM_STMT_PREPARE to MySQL
// and receives column and parameter metadata
stmt, err := preparer.PrepareContext(ctx, query)
if err != nil {
return err
}
defer stmt.Close()

// Access the metadata via the StmtMetadata interface from our forked driver
meta, ok := stmt.(mysql.StmtMetadata)
if !ok {
// Fallback: just use param count from NumInput
paramCount := stmt.NumInput()
for i := 1; i <= paramCount; i++ {
name := ""
if ps != nil {
name, _ = ps.NameFor(i)
}
result.Params = append(result.Params, &core.Parameter{
Number: int32(i),
Column: &core.Column{
Name: name,
DataType: "any",
NotNull: false,
},
})
}
return nil
}

// getColumnMetadata executes the query with default values to retrieve column information
func (a *Analyzer) getColumnMetadata(ctx context.Context, query string, paramCount int) ([]*core.Column, error) {
// Generate default parameter values (use 1 for all - works for most types)
args := make([]any, paramCount)
for i := range args {
args[i] = 1
}
// Get column metadata
for _, col := range meta.ColumnMetadata() {
result.Columns = append(result.Columns, &core.Column{
Name: col.Name,
DataType: strings.ToLower(col.DatabaseTypeName),
NotNull: !col.Nullable,
Unsigned: col.Unsigned,
Length: int32(col.Length),
})
}

// Wrap query to avoid fetching data: SELECT * FROM (query) AS _sqlc_wrapper LIMIT 0
// This ensures we get column metadata without executing the actual query
wrappedQuery := fmt.Sprintf("SELECT * FROM (%s) AS _sqlc_wrapper LIMIT 0", query)
// Get parameter metadata
paramMeta := meta.ParamMetadata()
for i, param := range paramMeta {
name := ""
if ps != nil {
name, _ = ps.NameFor(i + 1)
}
result.Params = append(result.Params, &core.Parameter{
Number: int32(i + 1),
Column: &core.Column{
Name: name,
DataType: strings.ToLower(param.DatabaseTypeName),
NotNull: !param.Nullable,
Unsigned: param.Unsigned,
Length: int32(param.Length),
},
})
}

rows, err := a.conn.QueryContext(ctx, wrappedQuery, args...)
if err != nil {
// If wrapped query fails, try direct query with LIMIT 0
// Some queries may not support being wrapped (e.g., queries with UNION at the end)
return nil, err
}
defer rows.Close()
return nil
})

colTypes, err := rows.ColumnTypes()
if err != nil {
return nil, err
}

var columns []*core.Column
for _, col := range colTypes {
nullable, _ := col.Nullable()
columns = append(columns, &core.Column{
Name: col.Name(),
DataType: strings.ToLower(col.DatabaseTypeName()),
NotNull: !nullable,
})
return nil, a.extractSqlErr(n, err)
}

return columns, nil
return &result, nil
}

// replaceDatabase replaces the database name in a MySQL DSN
Expand Down Expand Up @@ -253,47 +266,6 @@ func replaceDatabase(dsn string, newDB string) string {
return dsn[:slashIdx+1] + newDB + dsn[slashIdx+paramIdx:]
}

// countParameters counts the number of ? placeholders in a query
func countParameters(query string) int {
count := 0
inString := false
stringChar := byte(0)
escaped := false

for i := 0; i < len(query); i++ {
c := query[i]

if escaped {
escaped = false
continue
}

if c == '\\' {
escaped = true
continue
}

if inString {
if c == stringChar {
inString = false
}
continue
}

if c == '\'' || c == '"' || c == '`' {
inString = true
stringChar = c
continue
}

if c == '?' {
count++
}
}

return count
}

func (a *Analyzer) extractSqlErr(n ast.Node, err error) error {
if err == nil {
return nil
Expand Down
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