JACR: is_op, slow function analysed

[
  {
    "Plan": {
      "Node Type": "Aggregate",
      "Strategy": "Plain",
      "Partial Mode": "Simple",
      "Parallel Aware": false,
      "Startup Cost": 20373.66,
      "Total Cost": 20373.67,
      "Plan Rows": 1,
      "Plan Width": 8,
      "Actual Startup Time": 307.750,
      "Actual Total Time": 307.750,
      "Actual Rows": 1,
      "Actual Loops": 1,
      "Output": ["count(total_plays)"],
      "Shared Hit Blocks": 1361,
      "Shared Read Blocks": 0,
      "Shared Dirtied Blocks": 0,
      "Shared Written Blocks": 0,
      "Local Hit Blocks": 0,
      "Local Read Blocks": 0,
      "Local Dirtied Blocks": 0,
      "Local Written Blocks": 0,
      "Temp Read Blocks": 0,
      "Temp Written Blocks": 0,
      "Plans": [
        {
          "Node Type": "Seq Scan",
          "Parent Relationship": "Outer",
          "Parallel Aware": false,
          "Relation Name": "songs",
          "Schema": "public",
          "Alias": "songs",
          "Startup Cost": 0.00,
          "Total Cost": 20312.92,
          "Plan Rows": 24297,
          "Plan Width": 4,
          "Actual Startup Time": 3.398,
          "Actual Total Time": 307.684,
          "Actual Rows": 81,
          "Actual Loops": 1,
          "Output": ["total_plays"],
          "Filter": "is_op(songs.last_play, songs.recent_plays)",
          "Rows Removed by Filter": 72984,
          "Shared Hit Blocks": 1361,
          "Shared Read Blocks": 0,
          "Shared Dirtied Blocks": 0,
          "Shared Written Blocks": 0,
          "Local Hit Blocks": 0,
          "Local Read Blocks": 0,
          "Local Dirtied Blocks": 0,
          "Local Written Blocks": 0,
          "Temp Read Blocks": 0,
          "Temp Written Blocks": 0
        }
      ]
    },
    "Planning Time": 0.144,
    "Triggers": [
    ],
    "Execution Time": 307.789
  }
]