Graphile V5 Debugging

PostGraphile v5 Debugging

Debug schema generation issues and understand how PostGraphile v5 builds your GraphQL schema.

Official Documentation

• Debugging Guide: https://postgraphile.org/postgraphile/next/debugging
• Configuration: https://postgraphile.org/postgraphile/next/config

When to Apply

Use this skill when:

• You don't understand why a field is named a certain way
• You want to see what inflectors are being called
• You need to detect naming conflicts between schemas
• You're troubleshooting unexpected schema behavior
• You want to understand the build process

Graphile CLI Commands

PostGraphile v5 includes a graphile CLI toolbelt for debugging. These commands help you understand your configuration and schema generation.

Available Commands

graphile config print

Shows your resolved configuration after all presets merge:

npx graphile config print
npx graphile config print plugins  # Show enabled plugins

Use this when:

• Debugging configuration issues
• Verifying which plugins are loaded
• Checking configuration option values

graphile behavior debug

Debug behavior configurations with scope options:

npx graphile behavior debug

Supports scope options like pgResource, pgResourceUnique, and pgCodec to narrow down behavior debugging.

graphile inflection list

Lists all available inflectors with their arguments, documentation, and TypeScript definitions:

npx graphile inflection list

Use this when:

• Debugging naming/inflection issues
• Finding available inflector functions to override
• Understanding how database names become GraphQL names

DEBUG Environment Variables

Enable detailed logging with DEBUG environment variables:

# Schema construction warnings (often includes fixes)
DEBUG="graphile-build:warn" npx postgraphile ...

# Hook execution order
DEBUG="graphile-build:SchemaBuilder" npx postgraphile ...

# SQL query details
DEBUG="@dataplan/pg:PgExecutor" npx postgraphile ...

# SQL queries with EXPLAIN output
DEBUG="@dataplan/pg:PgExecutor:explain" npx postgraphile ...

Useful DEBUG Variables

Ruru Explain Tab

Enable the Explain tab in Ruru (the GraphQL IDE) to see query execution plans:

const preset: GraphileConfig.Preset = {
  grafast: {
    explain: true,  // Enable in development only
  },
};

Warning: Disable in production for security.

Understanding Schema Generation

PostGraphile v5 builds the schema once at startup:

1. Introspection - Reads database structure 2. Plugin Processing - Plugins modify the build 3. Inflection - Names are transformed 4. Type Generation - GraphQL types are created 5. Field Generation - Fields are added to types 6. Schema Finalization - Final schema is cached

Important: The schema is built ONCE and cached. Changes require server restart.

Inflector Logger Plugin

Log all inflector calls to understand naming:

import type { GraphileConfig } from 'graphile-config';

const LOG_ENABLED = process.env.INFLECTOR_LOG === '1';

function log(category: string, message: string, details?: Record<string, unknown>) {
  if (!LOG_ENABLED) return;
  const detailsStr = details ? ` ${JSON.stringify(details)}` : '';
  console.log(`[Inflector:${category}]${detailsStr} => ${message}`);
}

export const InflectorLoggerPlugin: GraphileConfig.Plugin = {
  name: 'InflectorLoggerPlugin',
  version: '1.0.0',

  inflection: {
    replace: {
      // Log query field names
      rowByUnique(previous, _options, details) {
        const result = previous!(details);
        const { unique, resource } = details;
        log('rowByUnique', result, {
          resource: resource.name,
          uniqueAttributes: unique.attributes,
          isPrimary: unique.isPrimary,
        });
        return result;
      },

      // Log forward relation names (post.author)
      singleRelation(previous, _options, details) {
        const result = previous!(details);
        const { codec, relationName, registry } = details;
        const relation = registry.pgRelations[codec.name]?.[relationName];
        log('singleRelation', result, {
          fromType: codec.name,
          relationName,
          toType: relation?.remoteResource?.name,
          localAttributes: relation?.localAttributes,
        });
        return result;
      },

      // Log backward relation names (user.posts)
      _manyRelation(previous, _options, details) {
        const result = previous!(details);
        const { codec, relationName, registry } = details;
        const relation = registry.pgRelations[codec.name]?.[relationName];
        log('manyRelation', result, {
          fromType: codec.name,
          relationName,
          toType: relation?.remoteResource?.name,
        });
        return result;
      },

      // Log root connection fields (Query.users)
      allRowsConnection(previous, _options, resource) {
        const result = previous!(resource);
        log('allRowsConnection', result, { resource: resource.name });
        return result;
      },

      // Log table type names
      tableType(previous, _options, codec) {
        const result = previous!(codec);
        log('tableType', result, { codec: codec.name });
        return result;
      },

      // Log attribute names
      attribute(previous, _options, details) {
        const result = previous!(details);
        const { attributeName, codec } = details;
        log('attribute', result, { codec: codec.name, attributeName });
        return result;
      },

      // Log update mutation names
      updateByKeysField(previous, _options, details) {
        const result = previous!(details);
        const { resource, unique } = details;
        log('updateByKeysField', result, {
          resource: resource.name,
          isPrimary: unique.isPrimary,
        });
        return result;
      },

      // Log delete mutation names
      deleteByKeysField(previous, _options, details) {
        const result = previous!(details);
        const { resource, unique } = details;
        log('deleteByKeysField', result, {
          resource: resource.name,
          isPrimary: unique.isPrimary,
        });
        return result;
      },
    },
  },
};

export const InflectorLoggerPreset: GraphileConfig.Preset = {
  plugins: [InflectorLoggerPlugin],
};

Usage

INFLECTOR_LOG=1 pnpm dev

Sample Output

[Inflector:tableType] {"codec":"users"} => User
[Inflector:rowByUnique] {"resource":"users","uniqueAttributes":["id"],"isPrimary":true} => user
[Inflector:rowByUnique] {"resource":"users","uniqueAttributes":["email"],"isPrimary":false} => userByEmail
[Inflector:allRowsConnection] {"resource":"users"} => users
[Inflector:singleRelation] {"fromType":"posts","relationName":"author","toType":"users"} => author
[Inflector:manyRelation] {"fromType":"users","relationName":"posts","toType":"posts"} => posts

Conflict Detector Plugin

Detect naming conflicts between tables in different schemas:

import type { GraphileConfig } from 'graphile-config';

interface CodecInfo {
  name: string;
  schemaName: string;
  tableName: string;
}

export const ConflictDetectorPlugin: GraphileConfig.Plugin = {
  name: 'ConflictDetectorPlugin',
  version: '1.0.0',

  schema: {
    hooks: {
      build(build) {
        const codecsByName = new Map<string, CodecInfo[]>();

        for (const codec of Object.values(build.input.pgRegistry.pgCodecs)) {
          if (!codec.attributes || codec.isAnonymous) continue;

          const pgExtensions = codec.extensions?.pg as { schemaName?: string } | undefined;
          const schemaName = pgExtensions?.schemaName || 'unknown';
          const graphqlName = build.inflection.tableType(codec);

          const info: CodecInfo = {
            name: graphqlName,
            schemaName,
            tableName: codec.name,
          };

          if (!codecsByName.has(graphqlName)) {
            codecsByName.set(graphqlName, []);
          }
          codecsByName.get(graphqlName)!.push(info);
        }

        for (const [graphqlName, codecs] of codecsByName) {
          if (codecs.length > 1) {
            const locations = codecs.map(c => `${c.schemaName}.${c.tableName}`).join(', ');
            console.warn(
              `\nNAMING CONFLICT: GraphQL type "${graphqlName}" from multiple tables:\n` +
              `   Tables: ${locations}\n` +
              `   Resolution options:\n` +
              `   1. Add @name smart tag: COMMENT ON TABLE schema.table IS E'@name UniqueTypeName';\n` +
              `   2. Rename one of the tables\n` +
              `   3. Exclude one table with @omit smart tag\n`
            );
          }
        }

        return build;
      },
    },
  },
};

export const ConflictDetectorPreset: GraphileConfig.Preset = {
  plugins: [ConflictDetectorPlugin],
};

Debugging Techniques

1. Print Schema to File

import { printSchema } from 'graphql';
import fs from 'fs';

// After building schema
const schema = pgl.getSchema();
fs.writeFileSync('schema.graphql', printSchema(schema));

2. Log Build Information

schema: {
  hooks: {
    build(build) {
      console.log('Available schemas:', build.options.pgSchemas);
      console.log('Number of codecs:', Object.keys(build.input.pgRegistry.pgCodecs).length);
      console.log('Number of resources:', Object.keys(build.input.pgRegistry.pgResources).length);
      return build;
    },
  },
},

3. Inspect a Specific Table

schema: {
  hooks: {
    build(build) {
      const { pgRegistry } = build.input;
      
      // Find a specific table
      const usersCodec = Object.values(pgRegistry.pgCodecs).find(
        c => c.name === 'users'
      );
      
      if (usersCodec) {
        console.log('Users codec:', {
          name: usersCodec.name,
          attributes: Object.keys(usersCodec.attributes || {}),
          extensions: usersCodec.extensions,
        });
      }
      
      return build;
    },
  },
},

4. Log All Generated Fields

schema: {
  hooks: {
    GraphQLObjectType_fields(fields, build, context) {
      const { Self } = context;
      console.log(`Fields for ${Self.name}:`, Object.keys(fields));
      return fields;
    },
  },
},

5. Check Behavior Resolution

schema: {
  entityBehavior: {
    pgResourceUnique: {
      override: {
        provides: ['debugBehavior'],
        callback(behavior, [resource, unique]) {
          console.log(`Behavior for ${resource.name}.${unique.attributes.join(',')}:`, behavior);
          return behavior;
        },
      },
    },
  },
},

Common Issues and Solutions

Field Not Generated

1. Check if table is in the schemas array 2. Check for @omit smart tags 3. Check behavior settings 4. Use InflectorLoggerPlugin to see if inflector is called

Wrong Field Name

1. Use InflectorLoggerPlugin to see what inflector produces 2. Check for @name smart tags 3. Check custom inflector overrides 4. Verify inflector plugin order in preset

Naming Conflict

1. Use ConflictDetectorPlugin to identify conflicts 2. Add @name smart tags to disambiguate 3. Check _schemaPrefix inflector behavior

Mutation Missing

1. Check table has primary key 2. Check for @omit create,update,delete smart tags 3. Check behavior settings for -insert, -update, -delete 4. Verify table is not a view

Filter Not Available

1. Check if column is indexed (default behavior) 2. Use EnableAllFilterColumnsPlugin 3. Check for -filterBy behavior on column 4. Verify connection filter plugin is installed

Complete Debug Preset

import type { GraphileConfig } from 'graphile-config';

export const DebugPreset: GraphileConfig.Preset = {
  plugins: [
    InflectorLoggerPlugin,
    ConflictDetectorPlugin,
  ],
};

// Usage
const preset: GraphileConfig.Preset = {
  extends: [
    MyAppPreset,
    DebugPreset,  // Add for debugging
  ],
};

Run with:

INFLECTOR_LOG=1 pnpm dev

Troubleshooting

Source Code References

• PgAttributesPlugin: https://github.com/graphile/crystal/blob/main/graphile-build/graphile-build-pg/src/plugins/PgAttributesPlugin.ts
• PgTablesPlugin: https://github.com/graphile/crystal/blob/main/graphile-build/graphile-build-pg/src/plugins/PgTablesPlugin.ts
• PgRelationsPlugin: https://github.com/graphile/crystal/blob/main/graphile-build/graphile-build-pg/src/plugins/PgRelationsPlugin.ts

References

• PostGraphile v5 Debugging Docs: https://postgraphile.org/postgraphile/next/debugging
• PostGraphile v5 Configuration Docs: https://postgraphile.org/postgraphile/next/config
• See graphile-v5-inflection skill for customizing inflectors
• See graphile-v5-plugins skill for creating custom plugins
• See graphile-v5-behaviors skill for understanding behaviors