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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[FEATURE] Predicate Push Down Abstract Implementation","articleBody":"**Feature Description**\r\nDesign and implement an abstract interface (through a provider's `x-stackQL-resources` object) to take advantage of predicate push down to limit data (columns and/or rows) returned. \r\n\r\n**Example(s)**\r\nGiven API operations which map to `SELECT` verbs in StackQL, identify the optional `query` parameters which can be mapped to the following operation:\r\n\r\n- column list for projection, invoked using `SELECT \u003cfield1\u003e, \u003cfield2\u003e` including fields operated on by scalar functions (such as `SPLIT_PART`, `JSON_EXTRACT`, etc.) \r\n- limiting records returned, invoked using `LIMIT \u003cnum\u003e`\r\n- filter expressions, invoked using `WHERE \u003cfield\u003e = '\u003csomething\u003e'`\r\n- ordering predicates, invoked using `ORDER BY \u003cfield\u003e`\r\n\r\nfor example...\r\n\r\n```yaml\r\n  parameters:\r\n    fields:\r\n      description: Selector specifying which fields to include in a partial response.\r\n      in: query\r\n      name: fields\r\n      schema:\r\n        type: string\r\n```\r\nCreate a document based interface to map verbs in the parser to the specified query parameters.\r\n\r\n**Possible Approaches or Libraries to Consider**\r\nA possible approach would be to create an extension to the provider interface for example...\r\n\r\n```yaml\r\ncomponents:\r\n    x-stackQL-resources:\r\n        databases:\r\n          id: google.spanner.databases\r\n          name: databases\r\n          title: Databases\r\n          methods:\r\n            projects_instances_databases_get:\r\n              operation:\r\n                $ref: '#/paths/~1v1~1projects~1{projectsId}~1instances~1{instancesId}~1databases~1{databasesId}/get'\r\n              response:\r\n                mediaType: application/json\r\n                openAPIDocKey: '200'\r\n            projects_instances_databases_list:\r\n              operation:\r\n                $ref: '#/paths/~1v1~1projects~1{projectsId}~1instances~1{instancesId}~1databases/get'\r\n              response:\r\n                mediaType: application/json\r\n                openAPIDocKey: '200'\r\n                objectKey: $.databases\r\n            ...\r\n          sqlVerbs:\r\n            select:\r\n              - $ref: '#/components/x-stackQL-resources/databases/methods/projects_instances_databases_get'\r\n              - $ref: '#/components/x-stackQL-resources/databases/methods/projects_instances_databases_list'\r\n            insert:\r\n              - $ref: '#/components/x-stackQL-resources/databases/methods/projects_instances_databases_create'\r\n            update: []\r\n            delete: []\r\n          predicates:\r\n            select:\r\n              rowFilter: \r\n                param: filter\r\n                example: \"column1 = 'value1' AND column2 = 'value2'\"\r\n              colFilter:\r\n                param: fields\r\n                example: \"column1,column2\"\r\n              orderBy:\r\n                param: orderBy\r\n                example: \"column1 ASC\"\r\n              limit:\r\n                param: limit\r\n                example: 10\r\n```\r\nmay need to implement generalized `format`s for each type of predicate.","author":{"url":"https://github.com/jeffreyaven","@type":"Person","name":"jeffreyaven"},"datePublished":"2023-10-03T01:08:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/223/stackql/issues/223"}