Updated Readme files

pkg/readers/pgsql/README.md

@@ -0,0 +1,138 @@
+# PostgreSQL Reader
+
+Reads schema information directly from a live PostgreSQL database.
+
+## Overview
+
+The PostgreSQL Reader connects to a PostgreSQL database and introspects its schema, extracting complete information about tables, columns, constraints, indexes, views, and sequences.
+
+## Features
+
+- Direct database introspection
+- Extracts complete schema information including:
+  - Tables and columns
+  - Primary keys, foreign keys, unique constraints, check constraints
+  - Indexes
+  - Views
+  - Sequences
+- Supports multiple schemas
+- Captures constraint actions (ON DELETE, ON UPDATE)
+- Derives relationships from foreign keys
+
+## Usage
+
+### Basic Example
+
+```go
+package main
+
+import (
+    "fmt"
+    "git.warky.dev/wdevs/relspecgo/pkg/readers"
+    "git.warky.dev/wdevs/relspecgo/pkg/readers/pgsql"
+)
+
+func main() {
+    options := &readers.ReaderOptions{
+        ConnectionString: "postgres://user:password@localhost:5432/mydb?sslmode=disable",
+    }
+
+    reader := pgsql.NewReader(options)
+    db, err := reader.ReadDatabase()
+    if err != nil {
+        panic(err)
+    }
+
+    fmt.Printf("Database: %s\n", db.Name)
+    fmt.Printf("Schemas: %d\n", len(db.Schemas))
+    for _, schema := range db.Schemas {
+        fmt.Printf("  Schema: %s, Tables: %d\n", schema.Name, len(schema.Tables))
+    }
+}
+```
+
+### CLI Example
+
+```bash
+# Inspect PostgreSQL database and export to JSON
+relspec --input pgsql \
+  --conn "postgres://user:password@localhost:5432/mydb" \
+  --output json \
+  --out-file schema.json
+
+# Generate GORM models from PostgreSQL database
+relspec --input pgsql \
+  --conn "postgres://user:password@localhost:5432/mydb" \
+  --output gorm \
+  --out-file models.go
+
+# Export database structure to YAML
+relspec --input pgsql \
+  --conn "postgres://localhost/mydb?sslmode=disable" \
+  --output yaml \
+  --out-file schema.yaml
+```
+
+## Connection String Format
+
+The reader uses PostgreSQL connection strings in the format:
+
+```
+postgres://username:password@hostname:port/database?parameters
+```
+
+Examples:
+```
+postgres://localhost/mydb
+postgres://user:pass@localhost:5432/mydb
+postgres://user@localhost/mydb?sslmode=disable
+postgres://user:pass@db.example.com:5432/production?sslmode=require
+```
+
+## Extracted Information
+
+### Tables
+- Table name and schema
+- Comments/descriptions
+- All columns with data types, nullable, defaults
+- Sequences
+
+### Columns
+- Column name, data type, length/precision
+- NULL/NOT NULL constraints
+- Default values
+- Auto-increment information
+- Primary key designation
+
+### Constraints
+- Primary keys
+- Foreign keys (with ON DELETE/UPDATE actions)
+- Unique constraints
+- Check constraints
+
+### Indexes
+- Index name and type (btree, hash, gist, gin, etc.)
+- Columns in index
+- Unique/non-unique
+- Partial indexes
+
+### Views
+- View definitions
+- Column information
+
+### Sequences
+- Sequence properties
+- Associated tables
+
+## Notes
+
+- Requires PostgreSQL connection permissions
+- Reads all non-system schemas (excludes pg_catalog, information_schema, pg_toast)
+- Captures PostgreSQL-specific data types
+- Automatically maps PostgreSQL types to canonical types
+- Preserves relationship metadata for downstream conversion
+
+## Requirements
+
+- Go library: `github.com/jackc/pgx/v5`
+- Database user must have SELECT permissions on system catalogs