feat(postgresql): add accurate analyzer mode for database-only analysis

Add an optional `analyzer.accurate: true` mode for PostgreSQL that bypasses
the internal catalog and uses only database-backed analysis.

Key features:
- Uses database PREPARE for all type resolution (columns, parameters)
- Uses expander package for SELECT * and RETURNING * expansion
- Queries pg_catalog to build catalog structures for code generation
- Skips internal catalog building from schema files

Configuration:
```yaml
sql:
  - engine: postgresql
    database:
      uri: "postgres://..."  # or managed: true
    analyzer:
      accurate: true
```

This mode requires a database connection and the schema must exist in the
database. It provides more accurate type information for complex queries.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: kyleconroy

internal/compiler/compile.go

@@ -1,6 +1,7 @@
 package compiler
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -39,6 +40,13 @@ func (c *Compiler) parseCatalog(schemas []string) error {
 		}
 		contents := migrations.RemoveRollbackStatements(string(blob))
 		c.schema = append(c.schema, contents)
+
+		// In accurate mode, we only need to collect schema files for migrations
+		// but don't build the internal catalog from them
+		if c.accurateMode {
+			continue
+		}
+
 		stmts, err := c.parser.Parse(strings.NewReader(contents))
 		if err != nil {
 			merr.Add(filename, contents, 0, err)
@@ -58,6 +66,15 @@ func (c *Compiler) parseCatalog(schemas []string) error {
 }
 
 func (c *Compiler) parseQueries(o opts.Parser) (*Result, error) {
+	ctx := context.Background()
+
+	// In accurate mode, initialize the database connection pool before parsing queries
+	if c.accurateMode && c.pgAnalyzer != nil {
+		if err := c.pgAnalyzer.EnsurePool(ctx, c.schema); err != nil {
+			return nil, fmt.Errorf("failed to initialize database connection: %w", err)
+		}
+	}
+
 	var q []*Query
 	merr := multierr.New()
 	set := map[string]struct{}{}
@@ -113,6 +130,18 @@ func (c *Compiler) parseQueries(o opts.Parser) (*Result, error) {
 	if len(q) == 0 {
 		return nil, fmt.Errorf("no queries contained in paths %s", strings.Join(c.conf.Queries, ","))
 	}
+
+	// In accurate mode, build the catalog from the database after parsing all queries
+	if c.accurateMode && c.pgAnalyzer != nil {
+		// Default to "public" schema if no specific schemas are specified
+		schemas := []string{"public"}
+		cat, err := c.pgAnalyzer.IntrospectSchema(ctx, schemas)
+		if err != nil {
+			return nil, fmt.Errorf("failed to introspect database schema: %w", err)
+		}
+		c.catalog = cat
+	}
+
 	return &Result{
 		Catalog: c.catalog,
 		Queries: q,

internal/compiler/engine.go

@@ -14,6 +14,7 @@ import (
 	sqliteanalyze "github.com/sqlc-dev/sqlc/internal/engine/sqlite/analyzer"
 	"github.com/sqlc-dev/sqlc/internal/opts"
 	"github.com/sqlc-dev/sqlc/internal/sql/catalog"
+	"github.com/sqlc-dev/sqlc/internal/x/expander"
 )
 
 type Compiler struct {
@@ -27,6 +28,15 @@ type Compiler struct {
 	selector selector
 
 	schema []string
+
+	// accurateMode indicates that the compiler should use database-only analysis
+	// and skip building the internal catalog from schema files
+	accurateMode bool
+	// pgAnalyzer is the PostgreSQL-specific analyzer used in accurate mode
+	// for schema introspection
+	pgAnalyzer *pganalyze.Analyzer
+	// expander is used to expand SELECT * and RETURNING * in accurate mode
+	expander *expander.Expander
 }
 
 func NewCompiler(conf config.SQL, combo config.CombinedSettings) (*Compiler, error) {
@@ -37,6 +47,9 @@ func NewCompiler(conf config.SQL, combo config.CombinedSettings) (*Compiler, err
 		c.client = client
 	}
 
+	// Check for accurate mode
+	accurateMode := conf.Analyzer.Accurate != nil && *conf.Analyzer.Accurate
+
 	switch conf.Engine {
 	case config.EngineSQLite:
 		c.parser = sqlite.NewParser()
@@ -56,10 +69,32 @@ func NewCompiler(conf config.SQL, combo config.CombinedSettings) (*Compiler, err
 		c.catalog = dolphin.NewCatalog()
 		c.selector = newDefaultSelector()
 	case config.EnginePostgreSQL:
-		c.parser = postgresql.NewParser()
+		parser := postgresql.NewParser()
+		c.parser = parser
 		c.catalog = postgresql.NewCatalog()
 		c.selector = newDefaultSelector()
-		if conf.Database != nil {
+
+		if accurateMode {
+			// Accurate mode requires a database connection
+			if conf.Database == nil {
+				return nil, fmt.Errorf("accurate mode requires database configuration")
+			}
+			if conf.Database.URI == "" && !conf.Database.Managed {
+				return nil, fmt.Errorf("accurate mode requires database.uri or database.managed")
+			}
+			c.accurateMode = true
+			// Create the PostgreSQL analyzer for schema introspection
+			c.pgAnalyzer = pganalyze.New(c.client, *conf.Database)
+			// Use the analyzer wrapped with cache for query analysis
+			c.analyzer = analyzer.Cached(
+				c.pgAnalyzer,
+				combo.Global,
+				*conf.Database,
+			)
+			// Create the expander using the pgAnalyzer as the column getter
+			// The parser implements both Parser and format.Dialect interfaces
+			c.expander = expander.New(c.pgAnalyzer, parser, parser)
+		} else if conf.Database != nil {
 			if conf.Analyzer.Database == nil || *conf.Analyzer.Database {
 				c.analyzer = analyzer.Cached(
 					pganalyze.New(c.client, *conf.Database),

internal/compiler/parse.go

@@ -71,7 +71,56 @@ func (c *Compiler) parseQuery(stmt ast.Node, src string, o opts.Parser) (*Query,
 	}
 
 	var anlys *analysis
-	if c.analyzer != nil {
+	if c.accurateMode && c.expander != nil {
+		// In accurate mode, use the expander for star expansion
+		// and rely entirely on the database analyzer for type resolution
+		expandedQuery, err := c.expander.Expand(ctx, rawSQL)
+		if err != nil {
+			return nil, fmt.Errorf("star expansion failed: %w", err)
+		}
+
+		// Parse named parameters from the expanded query
+		expandedStmts, err := c.parser.Parse(strings.NewReader(expandedQuery))
+		if err != nil {
+			return nil, fmt.Errorf("parsing expanded query failed: %w", err)
+		}
+		if len(expandedStmts) == 0 {
+			return nil, errors.New("no statements in expanded query")
+		}
+		expandedRaw := expandedStmts[0].Raw
+
+		// Use the analyzer to get type information from the database
+		result, err := c.analyzer.Analyze(ctx, expandedRaw, expandedQuery, c.schema, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		// Convert the analyzer result to the internal analysis format
+		var cols []*Column
+		for _, col := range result.Columns {
+			cols = append(cols, convertColumn(col))
+		}
+		var params []Parameter
+		for _, p := range result.Params {
+			params = append(params, Parameter{
+				Number: int(p.Number),
+				Column: convertColumn(p.Column),
+			})
+		}
+
+		// Determine the insert table if applicable
+		var table *ast.TableName
+		if insert, ok := expandedRaw.Stmt.(*ast.InsertStmt); ok {
+			table, _ = ParseTableName(insert.Relation)
+		}
+
+		anlys = &analysis{
+			Table:      table,
+			Columns:    cols,
+			Parameters: params,
+			Query:      expandedQuery,
+		}
+	} else if c.analyzer != nil {
 		inference, _ := c.inferQuery(raw, rawSQL)
 		if inference == nil {
 			inference = &analysis{}

internal/config/config.go

@@ -124,6 +124,7 @@ type SQL struct {
 
 type Analyzer struct {
 	Database *bool `json:"database" yaml:"database"`
+	Accurate *bool `json:"accurate" yaml:"accurate"`
 }
 
 // TODO: Figure out a better name for this

internal/config/v_one.json

@@ -80,6 +80,9 @@
                         "properties": {
                             "database": {
                                 "type": "boolean"
+                            },
+                            "accurate": {
+                                "type": "boolean"
                             }
                         }
                     },

internal/config/v_two.json

@@ -83,6 +83,9 @@
                         "properties": {
                             "database": {
                                 "type": "boolean"
+                            },
+                            "accurate": {
+                                "type": "boolean"
                             }
                         }
                     },