{
  "$schema": "https://json-schema.org/draft/2020-12",
  "$id": "https://electric.ax/schemas/subset-snapshot",
  "title": "SubsetSnapshot",
  "description": "Response object returned by the Electric HTTP API when any subset__* parameters are present. Contains a data array of operation messages and PostgreSQL snapshot metadata.",
  "type": "object",
  "required": ["data", "metadata"],
  "properties": {
    "metadata": {
      "type": "object",
      "description": "PostgreSQL snapshot metadata used by clients to determine which subsequent change-stream events to skip.",
      "properties": {
        "xmin": {
          "type": "string",
          "description": "Minimum active transaction ID at snapshot time (uint64 as string)."
        },
        "xmax": {
          "type": "string",
          "description": "Next transaction ID that had not yet started at snapshot time (uint64 as string)."
        },
        "xip_list": {
          "type": "array",
          "items": { "type": "string" },
          "description": "Transaction IDs that were in-progress during the snapshot (uint64 as strings)."
        },
        "snapshot_mark": {
          "type": "integer",
          "description": "Random number identifying this snapshot, matching snapshot_mark in operation headers."
        },
        "database_lsn": {
          "type": "string",
          "description": "PostgreSQL write-ahead log sequence number at snapshot time."
        }
      }
    },
    "data": {
      "type": "array",
      "description": "Array of operation messages representing the subset snapshot data (no control messages).",
      "items": {
        "type": "object",
        "properties": {
          "headers": {
            "type": "object",
            "properties": {
              "operation": {
                "type": "string",
                "enum": ["insert", "update", "delete"]
              },
              "snapshot_mark": {
                "type": "integer"
              },
              "lsn": { "type": "string" },
              "op_position": { "type": "integer" },
              "txids": {
                "type": "array",
                "items": { "type": "string" }
              }
            }
          },
          "key": { "type": "string" },
          "value": {
            "type": "object",
            "additionalProperties": { "type": "string" }
          },
          "old_value": {
            "type": "object",
            "additionalProperties": { "type": "string" }
          }
        }
      }
    }
  }
}